committee on materials and pavements€¦ · j. mp 23(2014) – reclaimed asphalt shingles for use...

Tech Subcommittee 2d Annual Meeting 2020 of 9

COMMITTEE ON MATERIALS AND PAVEMENTS

Meeting (Annual or Mid-Year) Annual Date August 4th Scheduled Time 10:00 AM Mountain Daylight Time Technical Subcommittee & Name 2d – Proportioning of Asphalt Aggregate Mixtures Chair Name and (State) Oak Metcalfe (MT) Vice Chair Name and (State) Greg Milburn (WY) Research Liaison Name and (State)

Vacant (Any volunteers??)

I. Introduction and Housekeeping

II. Call to Order and Opening Remarks

Our main goal today is to address the TS Ballots from earlier in the year, get task force updates, and introduce a few new revisions.

If you would like to be a member please reach out to Oak and Casey to be added to the list. Two hundred and fifty-two (252) people registered and two hundred and nineteen (219) people attended.

III. Roll Call of Voting Members

Present Member Name State Present Member Name State ☒ Michael San Angelo (Steve

Saboundjian present) AK ☒ Brett Trautman & Shane Adams MO

☒ Scott George AL ☒ Oak Metcalfe MT (Chair)

☒ Jesus Sandoval-Gil AZ ☒ Charlie Pan NV ☒ Jonathan Annable AR ☒ Russell Thielke NY ☒ Craig Wieden CO ☒ Todd Whittington NC ☒ Robert Lauzon (Scott Zakszewski

present) CT ☒ Eric Biehl OH

☒ Jennifer Pinkerton (Erin Osbourne & Mark Schaffer present)

DE ☒ Matt Romero OK

☐ Rezene Medhani DC ☒ Larry Ilg (Sean Parker & Others present)

OR

☒ Wayne Rilko (Howie Mosley & Greg Sholar present)

FL ☒ Anne Holt ON

☒ Jacob Walker GA ☒ Tim Ramirez PA ☐ Anita Joaquin HI ☒ Michael Byrne RI ☒ Mike Santi (Lori Copeland

present) ID ☒ Tom Grannes (proxy) SD

☒ Brian Pfeifer IL ☒ Michael Doran TN ☒ Matt Beeson IN ☒ Scott Nussbaum UT ☒ Rick Barenzinsky KS ☒ Aaron Schwartz VT ☒ Allen Myers KY ☒ Robert Crandol (Andy Babish

present) VA

☒ Chandra Akisetty (proxy) MD ☒ Kurt Williams WA ☒ Casey Nash ME ☒ Barry Pate WI ☒ Clement Fung MA ☒ Greg Milburn WY (Vice) ☒ Curt Turgeon (John Garrity

present) MN


Quorum Rules Met? Yes Annual Meeting: Simple majority of voting members (☐y/ ☐n)

A. Review of Membership (New members, exiting members, etc.)

1. Replace Brian Egan with Mike Doran in membership

B. The Chair gave honors to the late Becky McDaniel who ran the Purdue research lab and was a huge positive influence on the community. We observed a moment of silence for Becky.

IV. Approval of Technical Subcommittee Minutes

A. Attachment A (pp. 6-11) Motion to approve minutes with changes below: MO

Second by AZ Add Missouri to the meeting minutes, as well as Eric Biehl (OH) and moves to accept the minutes as changed.

V. Old Business

A. No outstanding COMP Ballot items. Review of new published standards: 2. MP 46 – Standard Specification for Balanced Mix Design 3. PP 105 – Standard Practice for Balanced Design of Asphalt Mixtures 4. TP 140 – Standard Method of Test for Moisture Sensitivity Using Hydrostatic Pore Pressure to

Determine Cohesion and Adhesion Strength of Compacted Asphalt Mixture Specimens 5. TP 141 – Standard Method of Test for Determining the Indirect Tensile Nflex Factor to Assess the

Cracking Resistance of Asphalt Mixtures (Note from Midyear minutes says we need to ballot the use of a 25°C environmental chamber (FL comment) but that language is already in there.)

B. R35 and Kerosene just won’t go away 😊😊…Spoke to Andy Babish and Griffin Sullivan (TS 1a). T 100 isn’t going anywhere soon. Based on this and the comments previously submitted, will leave existing reference in R 35 and drop this from the agenda. Andy and Griffin have assured me they will let me know if anything is proposed to T100 that would affect this.

C. TP 107 – Did not add PP99 and TP 133 to list of references, however, work is going on to revise TP 107 so hopefully that will take care of this.

D. Technical Subcommittee Ballots TS Ballot # Standard

Results (neg/affirm) Comments/Negatives Action

20-01 T 283 1/20 Gerry Huber: Section 10.4.2, Note 4 70 and 80 percent should be 70 to 80 percent

Done

T 283 – Resistance of Compacted Asphalt Mixtures to Moisture- Induced Damage

FL: We wish to retain the ability to test roadway cores per T 283.

Done (there was a request to remove ability to remove roadway cores so it was left in)

(Attachment B – pp. 12-23) IL: ASTM D3387/D979, pan depth, “air void content”, achieving air void content, Pa

Discuss (This std is listed as a reference but has been w/drawn from ASTM.)

NV: Time frame before testing, NCHRP 444 Discuss MA: Pa Make change ON: “gyrations”, 24hrs, add “cores” to 8.2,

SGC definition Make editorial changes, discuss

MO: 24hr cure time, doing their own research

Discuss

KY: 24hr cure time Discuss OH: Negative (withdrawn/addressed)

regarding measurement accuracy, enough mix for two specimens, add adjust SGC

Addressed negative, make editorial changes, discuss




height, “gyrations”, visual degree of stripping

UT: 24hr cure time Cure time seems to be the biggest, most common comment. (MO): Performed in-house study and noted a difference in results based on core (1-3% drop in dry set). Noted that breaking them early made the TSR results “better” (NV): Agrees with MO. Intent is to break dry and wet set at the same time, likes the change

Discuss

Motion to move these changes to T 283 full COMP ballot Motion by MO Second by WI T283 will be moved to a COMP ballot with changes 20-02 TP 124

(appendix) 0/33 FL: General comments on proposed aging 9-54 project recommends 95C,

time is based on location. TP 124 - Determining the Fracture Potential of Asphalt Mixtures Using the Illinois Flexibility Index Test (I-FIT)

PA: Editorial and Style comments, discussion on aging at 95C

Discuss

(Attachment C – pp. 24-25, 28-54) NV: Comment on air void tolerance, T283? Discuss TN: “specimens” instead of “bricks” Make editorial change ON: Add traffic category to list of factors,

air void tolerance, “similar”, notch width, hours vs days, definition of “cool”

Discuss

Presentation by Prof. Imad Al-Qadi (attached) – discussed I-FIT test (TP-124). Emphasized you must have a notch because it’s a fracture test. If there’s no fracture it’s just a strength test. I-FIT distinguishes between fracture energy. Discussed material scenarios and aggregate/matrix arrangement and mix design. Will substantially change results. Crack speed is responsible for the coefficient of variation. Captures inherent variability of AC MN moves to add changes to TP 124 and make a COMP ballot. MD seconds. No discussion. This will be added to a COMP ballot 20-02 TP 124

(full standard)

0/33 None Call for motion

Motion to move TP 124 to a full standard by VT Second by NY. No discussion. This will be added to a COMP ballot. 20-02 TP 133 0/33 PA: Style and editorial comments Refer to author TP 133 - Determining the Damage Characteristic Curve and Failure Criterion Using Small Specimens in the Asphalt Mixture Performance Tester (AMPT) Cyclic Fatigue Test

NV: Clarifying comments Refer to author

(Attachment C – pp. 26-27, 55-89) MO: Formatting comments Refer to author TN: LVDT, 6.2 Refer to author KY Motion to change the wording in the comments to full COMP ballot MO seconds. No discussion

E. Task Force Reports


Task Force # Title Members Status/Update 19-01 R 30 Revisions OH-Chair, WA, MT, OR,

MD Some of the sections in R30 were out of place; waiting on the results of some of te 20-44 projects to try to incorporate the results into this TF

19-02 T 340

OH-Chair, PA, GA May create some specimens to compare APA and APA Junior

VI. New Business

A. AASHTO re:source (Observations from assessments, as applicable.)

B. Presentation by Industry/Academia – Mississippi DOT & Mississippi State presentation – Griffin Sullivan, MS and Dr. Issac Howard, MSU – 15 mins (Webinar attachments ‘TP 108’ and ‘RTrack’)

RTrack - Testing while dry, testing while wet, and then comparing the difference is the standout feature of Rtrack TP 108 – Dr. Howard would like to submit changes to TP 108 to broaden language to include dense

graded mixes. Would also like to add appendix that includes conditioning protocols.

C. Revisions/Work on Standards for Coming Year Standard # Title Task/Summary Assigned to T 312 Preparing and Determining

the Density of Asphalt Mixture Specimens by Means of the Superpave Gyratory Compactor

Editorial changes from WAQTC (Attachment D – p. 90) Chair

M 323 Superpave Volumetric Mix Design

Proposed Revisions (Attachment E – pp. 91-109) Indiana

R 35 Superpave Volumetric Design for Asphalt Mixtures

Proposed Revisions (Attachment F – p. 110-140) Indiana

Discussion on M 323 and R 35: rolling in the work of superpave 5. This may be the cleanest way of incorporating the other design methodology. There is also information about incorporating RAP as binder replacement. How should this be incorporated? Appendix? Addendum? Separate document entirely? IN: reiterated Chair’s comments above, opened up comments to the group – MN requested that IN prepare a superpave 5 standalone standard so COMP could see what it looks like WA: suggests having a webinar prior to balloting to get everything squared away before a ballot. Would like to see case studies to validate changes before getting too far down the road WI: this started off by trying to find the best way to get the superpave 5 information into the hands of users. If you’re going to do SP5 you have to do it all – if it gets blended into M 323 then some of it might be lost. Trying to find the cleanest way to do this. If it’s stand-alone will probably have to refer back or copy a lot of M 323 Jim Musselman (Auburn): available for research. Randy West – this discussion is only in reference to virgin binder grade (table 2 in M 323) when RAP/Binder ratio exceeds a certain amount ME: As part of this discussion, I suggest we include the findings of 20-07/Task 412 TS will work with AASHTO to arrange a webinar towards the end of 2020

D. Review of Standards up for reconfirmation/Stewardship List 1. Full standards

a. M 323-17 – Superpave Volumetric Mix Design – (Underway) Next Year b. M 325-08(2017) – Stone Matrix Asphalt (SMA) – Next Year c. R 35-17 – Superpave Volumetric Mix Design for Asphalt Mixtures – (Underway) Next Year d. R 46-07(2017) – Designing Stone Matrix Asphalt – Next Year e. R 62-13(2017) – Developing Dynamic Modulus Master Curves for Asphalt Mixtures – Next

Year f. R 83-17 – Preparation of Cylindrical Performance Test Specimens Using the Superpave

Gyratory Compactor (SGC) – Next Year g. R 84-17 – Developing Dynamic Modulus Master Curves for Asphalt Mixtures Using the

Asphalt Mixture Performance Tester (AMPT) – Next Year


h. T 321-17 – Determining the Fatigue Life of Compacted Asphalt Mixtures Subjected to Repeated Flexural Bending – Next Year

i. T 378-17 – Determining the Dynamic Modulus and Flow Number for Asphalt Mixtures Using the Asphalt Mixture Performance Tester (AMPT) – Next Year

2. Provisional Standards (Provisional Year in Parentheses) j. MP 23(2014) – Reclaimed Asphalt Shingles for Use in Asphalt Mixtures– 1-year extension this

year (last provisional extension) k. PP 76(2013) – Troubleshooting Asphalt Specimen Volumetric Differences between Superpave

Gyratory Compactors (SCGs) Used in the Design and the Field Management of Superpave Mixtures – Adopt or Drop for 2021 Publication

a. Motion to adopt the standard by MN; OR seconds. No discussion l. PP 77(2014) – Materials Selection and Mixture Design of Permeable Friction Courses – 1-year

extension this year (last provisional extension) m. PP 78(2014) – Design Considerations When Using Reclaimed Asphalt Shingles (RAS) in

Asphalt Mixtures – 1-year extension this year (last provisional extension) n. PP 99(2019) – Preparation of Small Cylindrical Performance Test Specimens Using the

Superpave Gyratory Compactor (SGC) or Field Cores – 2-year extension this year o. TP 105(2013) – Determining the Fracture Energy of Asphalt Mixtures Using the Semicircular

Bend Geometry (SCB) – Adopt or Drop for 2021 Publication a. Motion to adopt the standard into full std: ONT; second by OK. No discussion

p. TP 107(2014) – Determining the Damage Characteristic Curve of Asphalt Mixtures from Direct Tension Cyclic Fatigue Tests – 1-year extension this year (last provisional extension)

q. TP 108(2014) – Abrasion Loss of Asphalt Mixture Specimens – 1-year extension this year (last provisional extension)

r. TP 116(2015) – Rutting Resistance of Asphalt Mixtures Using Incremental Repeated Load Permanent Deformation (iRLPD) – 1-year extension next year (Haleh Azari may still need volumetric samples for P&B work)

s. TP 117(2015) – Determination of the Voids of Dry Compacted Filler – 1-year extension next year

t. TP 124(2016) – IFIT – 2-year extension next year (potentially move to full standard from above)

u. TP 125(2016) – Determining the Flexural Creep Stiffness of Asphalt Mixtures Using the Bending Beam Rheometer (BBR) – 2-year extension next year

v. TP 131(2018) – Determining Dynamic Modulus of Asphalt Concrete Using the Indirect Tension Test – 2-year extension next year

w. TP 132(2019) – Determining the Dynamic Modulus for Asphalt Mixtures Using Small Specimens in the Asphalt Mixture Performance Tester (AMPT) – 2-year extension this year

x. TP 133(2019) – Determining the Damage Characteristic Curve and Failure Criterion Using Small Specimens in the Asphalt Mixture Performance Tester (AMPT) Cyclic Fatigue Test – 2-year extension this year

y. TP 134(2019) – Stress Sweep Rutting (SSR) Test Using Asphalt Mixture Performance Tester (AMPT) – 2-year extension this year

E. NCHRP Issues 1. NCHRP 20-07/Task 427 Developing a Recommended AASHTO Standard Practice for Selection of

Temperature-Measuring Devices (FYI – Previously discussed throughout the COMP Meeting) 2. RNS Submitted by Illinois – Recycled Binder Availability (Webinar attachment ‘RNS’)

F. Correspondence, Calls, Meetings


1. FHWA Asphalt Materials Research Program Mixture Performance Test Comparison Study is looking for States to provide mixture samples – Dave Mensching, FHWA (p. 141)

2. TFASH is looking for members with expertise in asphalt mixtures – Joe Kerstetter, TNDOT TS 2d has 3 standards in TFASH

G. Proposed New Task Forces (Include list of volunteers to lead and/or join TF.)

H. New TS Ballots 1.

VII. Open Discussion

A.

B.

VIII. Adjourn

TS Meeting Summary

Meeting Summary Items Approved by the TS for Ballot (Include reconfirmations.)

Standard Designation Summary of Changes Proposed Ballot Type

T 283 – Resistance of Compacted Asphalt Mixtures to Moisture- Induced Damage

Editorial changes, curing time, ability to test road cores

☐TS ☒COMP ☐CONCURRENT TP 124 - Determining the Fracture Potential of Asphalt Mixtures Using the Illinois Flexibility Index Test (I-FIT)

Make changes noted in table

☐TS ☒COMP ☐CONCURRENT TP 124 - Determining the Fracture Potential of Asphalt Mixtures Using the Illinois Flexibility Index Test (I-FIT)

Move to full standard (does this need to be a second ballot item or can it be combined with previous item?)

☐TS ☒COMP ☐CONCURRENT TP 133 - Determining the Damage Characteristic Curve and Failure Criterion Using Small Specimens in the Asphalt Mixture Performance Tester (AMPT) Cyclic Fatigue Test

Make changes noted in table then move to COMP ballot with changes

☐TS ☒COMP ☐CONCURRENT PP 76(2013) – Troubleshooting Asphalt Specimen Volumetric Differences between Superpave Gyratory Compactors (SCGs) Used in the Design and the Field Management of Superpave Mixtures

Adopt as full standard

☐TS ☒COMP ☐CONCURRENT TP 105(2013) – Determining the

Adopt as full standard ☐TS ☒COMP ☐CONCURRENT


Meeting Summary Fracture Energy of Asphalt Mixtures Using the Semicircular Bend Geometry (SCB) ☐TS ☐COMP ☐CONCURRENT New Task Forces Formed

Task Force Name Summary of Task TF Member Names and (States)

No new TF Research Proposals (Include number/title/states interested.) Other Action Items Plan for a late 2020 webinar to discuss M 323, R35, and superpave 5 IN will draft a stand-alone superpave 5 standard to present to the committee

Metcalfe, Oak

From: Metcalfe, Oak Sent: Wednesday, August 5, 2020 5:09 PM To: '[email protected]' Cc: Mensching, David (FHWA); Joseph Kerstetter; Michael Doran; Scott

Veglahn; Howard, Isaac; Haleh Azari; [email protected] Subject: Follow up from TS2d Virtual Session

Greetings everyone, Thanks again to all who participated in the TS2d Virtual Meeting on Tuesday of this week, I

know we didn’t answer all the questions at hand, but we got a good deal accomplished and a direction forward. Because we didn’t really have enough time for questions and answers, I wanted to try and tie all those together here and give folks the opportunity to either ask questions of or get in touch with the folks who presented or were looking for volunteers or mixture samples. I’ve included email addresses in the cc line of this email in case anyone wants to get in touch with folks directly, but I am happy to pass along names to the appropriate folks if you’d prefer.

So…

We saw Professor Imad Al-Qadi’s (University of Illinois) presentation on the IFIT and variability. As was discussed during the call, we’ll make that presentation available to everyone via the COMP website. But if anyone has any questions on variability or comparing fracture energy to strength (the latter portion of the presentation) feel free to send them and I’ll pass them on to Professor Al-Qadi.

mailto:[email protected]


We heard from Professor Isaac Howard (Mississippi State University) and the work he’s doing on the RTrack rutting test as well as TP 108 – Cantabro. As discussed on the call, TP 108 is in it’s provisional status so I encouraged him to work on a draft to include the revisions he discussed and will be happy to put that in front of the TS at the appropriate time. As far as the RTrack, we didn’t get much time to discuss that, so if anyone has any questions feel free to send them and I’ll pass them on to Professor Howard. In addition, if any states out there are interested in working with Mississippi and MSU on this, I will gladly pass your name along.

I mentioned the ongoing ASTM – AASHTO Harmonization effort (TFASH) and the need for mixture subject matter experts to participate in the effort. While there are only the three standards I mentioned on the call relevant to this committee (2d), there are other standards in 2c that could use the assistance and the same TFASH group is working on all of them. I mentioned Mike Doran and Joe Kerstetter from Tennessee DOT on the call but forgot to mention Scott Veglahn from Mathy Construction who I believe is representing ASTM on the committee. If you’d like to assist in that effort feel free to send me your name and I’ll pass it along to the group.

I also mentioned a few research efforts going that could benefit from mixture samples…

Haleh Azari with Pavement Systems LLC is looking for volumetric mixture samples to assist in developing a precision and bias statement for TP 116, the iRLPD (incremental Repeated Load Permanent Deformation) test. If you’d like to help out, feel free to contact me and I and will put you in touch with Haleh. And finally, …

Dave Mensching at FHWA’s Turner Fairbanks Research Center Asphalt Materials Research Program is leading a comparison study on Mixture Performance Tests and is looking for samples of loose mixture from DOTs to perform cracking test comparisons. If you’d like to help out, feel free to contact me and I and will put you in touch with Dave.

Again, all these folks are cc’d above so you can reach out to them directly if you have questions or would like more information, but I’m happy to act as an intermediary.

I think that was all I wanted to follow up on, at least for now, with this group. I’m working on getting the minutes finalized from yesterday and I’ll be back in touch with everyone to start sorting out when the best time would be for a webinar on the ongoing M 323/R35 discussion. I figure we’re still in the thick of construction season and COVID19, not to mention the COMP meeting is still going on. But I don’t want to wait to long. I don’t think folks are going to forget about this, but with more and more meetings going virtual, schedules will start to fill up soon.

Thank you again for the good discussion yesterday on the call and for your continued patience with me and my shenanigans as chair :..; -

Stay safe and we’ll “see” you at the next webinar.


Ross “Oak” Metcalfe,

P.E. State Materials

Engineer 406-444-9201

[email protected]

“Nullius in Verba”

mailto:[email protected]

Tech Subcommittee 2d Mid-year Meeting 2020 Page 1 of 6

COMMITTEE ON MATERIALS AND PAVEMENTS

Meeting (Annual or Mid-Year) Mid-year Date January 22nd, 2020 Scheduled Time 12:00 PM – 2:00 PM MST Technical Subcommittee & Name TS2d – Proportioning of Asphalt-Aggregate Mixtures Chair Name and (State) Oak Metcalfe – MT Vice Chair Name and (State) Greg Milburn – WY Research Liaison Name and (State) Open – Any Volunteers???

I. Introduction and Housekeeping

II. Call to Order and Opening Remarks

A. Today’s goals are to address the 2019 Rolling and reconfirmation ballot items and to hear Task Force updates.

III. Roll Call of Voting Members

Present Member Name State Present Member Name State Present AL NV AK NY AZ OH Michael Benson AR OK Craig Wieden CO Imran Bashir ON Bob Lauzon CT Larry ilg OR Jennifer Pinkerton DE PA DC RI Wayne Rilko FL SD GA Mike Doran TN HI Scott Nussbaum UT ID Aaron schwarts VT Brian Hill IL Rob Crandal VA IN Joe Devol WA KS WI Allen Myers KY WY ME Rick Bradbury MA MN MO Oak Metcalfe MT

Quorum Rules Met? Annual Meeting: Simple majority of voting members ( y/ n) | Mid-Year Meeting: Voting members present ( y/ n)

A. Review of Membership (New members, exiting members, etc.)

IV. Approval of Technical Subcommittee Minutes

Attachment A

Motion by Missouri second Wisconsin motion passed

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Tech Subcommittee 2d Mid-Year Meeting 2020 Page 2 of 6

V. Old Business

(Outstanding or action items from previous meeting; use Heading 1 through Heading 6 styles to get outline format.)

A. R35 and Kerosene as a wetting agent 1. This keeps falling off my radar, so I need to get with Andy Babish (TS1a). This was requested by

AASHTO RE:source.

B. TP 105 machining tolerances 2. Didn’t provide an updated figure for balloting purposes, waiting for the figure from AASHTO pubs.

C. COMP Ballot Items (Include any ASTM changes/equivalencies, including ASTM standards’ revision years.) COMP Ballot # Standard


22 MP XXX BMD

0/42 FL - Section 6.9. The typical ESALs per traffic level shown in Table 12 are not duplicated in Appendix X.1, Table X.6. Table X.6, 1000,000 should be 1,000,000.

Editorial – make change.

MA - Appendix X.1.2 Table X.2 - MassDOT test temperature is 45°F.

Editorial – make change 45 deg C

SC - Would prefer some guidance for test criteria. Basically, I assume we need to establish our state's limitations / local calibration for this guidance?

Publish and see how it is used and at the end of the 2 years, then have discussion if it is working and we want to keep it going. Randy West said they are setting up a webinar to teach how to use the provisional specification. Possible new task force any volunteers for Chair of Task force?

23 PP XXX BMD

0/42 None

24 TP XXX (M.I.S.T.)

0/42 KS - 2.1 AASHTO T 168 is withdrawn and replaced with R 97

Editorial – make change

25 TP XXX (Nflex)

0/42 FL - Add a provision for use of a 25 degree C air chamber.

Not editorial, will be balloted next year so it can be included in the next cycle

26 TP 116 0/42 None 27 TP 124 0/42 VT - Note 6 seems out of place. Add Illinoi’s long term aging

procedure to Appendix Leave note 6 as and move to publish

28 TP 105 0/42 None



22 MP XXX BMD

0/30 D’Angelo - At best this should be a procedure for how to set up a specification for BMD. It should describe how to evaluate if a test is appropriate for a locations and how to set the limits as seen in the next item. it is not ready for a M specification.

There was a long discussion on this topic, nothing was decided, Chair felt like a task force was needed to get more states input before anything is decided.

FHWA - I find this document to be onerous to update and really not an appropriate location for a directory of what states are

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doing for performance testing. Suggest this be explored in more detail (the proper location for a directory of this nature). Who will be responsible for updating this, especially when an overwhelming majority of States do not have criteria set for a particular test? The reference section is not up to date with emerging tests (such as AASHTO TP 116, TP 133, TP 134, TP 108). What constitutes when a test should be referenced in this document or not? For example, why is UTSST or BBR slivers included, but not Cantabro? Is a test referenced when a State is using for research-level work? Full-blown implementation via standard specification language? There needs to be documented objectivity in when or how a certain test is included in this document.

23 PP XXX BMD

0/30 FHWA - Title: the title doesn't tell us enough about what the practice entails. A title should include the terms "performance tests" at a bare minimum and remove "balanced", which can be misleading (if rutting isn't a concern why is it being "balanced" with cracking resistance). Mixture design using performance tests should focus on optimization of materials and proportioning to achieve field performance goals. This practice is focused on asphalt content alone (with the exception of language when moisture damage tests fail), which does not encourage the degree of innovation possible using a technique such as a performance-based/related mixture design. Section 1.1: this should be rephrased. There is little indication that the design will be "balanced" simply by using performance tests without a myriad of additional information on how these materials actually perform in the field. I recommend instead: This standard practice serves as a framework for design of asphalt mixtures using volumetric and/or performance test results.

Dave Mensching explained that the definitions and terms could be improved to make it clearer. Performance tests to design the mix

24 TP XXX (M.I.S.T.)

0/30 OH - Section 9.4.1.2: Missing deg C after the 35. Section 9.6: What if the drain valve doesn't open? Section 10.1.2: Space needed between R and 79.

Make editorial changes Oak will follow up with the authors about the drain valve question. Will move forward to publish

25 TP XXX (Nflex)

0/30 None

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26 TP 116 0/30 None Can the states send volumetric samples to Haleh Azari for precision and bias work. Oak will send out a request to states

27 TP 124 0/30 Was the precision and bias work done in accordance with ASTM E691 or other standardized procedure?

Yes. ILDOT worked with AASHTO Resource to make sure they were following E691

E. Reconfirmation Ballots Reconf. Ballot # Standard


1 T 320 0/32 None Approve as is – 4 yrs. 2 T 322 0/32 None Approve as is – 4 yrs. 3 T 344 0/32 None Approve as is – 4 yrs. 4 MP 38 0/32 None Extend 2 years 5 PP 94 0/32 None Extend 2 years 6 PP 95 0/32 None Extend 2 years 7 PP 96 0/32 None Extend 2 years 8 TP 125 0/32 None Extend 2 years 9 TP 131 0/32 None Extend 2 years 10 MP 23 0/32 None Extend 1 year 11 PP 76 0/32 None Extend 1 year 12 PP 77 0/32 None Extend 1 year 13 PP 78 0/32 None Extend 1 year 14 TP 107 0/32 None Extend 1 year 15 TP 108 0/32 None Extend 1 year

F. Task Force Reports Task Force # Title Members Status/Update 19-01 R30 Revisions OH – Chair, WA, MT, OR,

MD Change HMA to Asphalt mixture, Cooling test specimen for 16 hours plus or minus 1 hour why is it here and not in other places?

19-02 T340 OH – Chair, PA, GA Manufacturer wanted to have updated to let new equipment that uses 4 specimens and not 6 be used. Have a mini round robin to see if states are seeing any differences in the equipment

VI. New Business

A. AASHTO re:source/NTPEP - None

B. Presentation by Industry/Academia - None

C. Revisions/Work on Standards for Coming Year Standard # Title Task/Summary Assigned to TP 107 Add PP 99 and TP 133 to list of referenced standards Chair

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No direct references to PP 99 and TP 133 in TP 107, will probably add a new section to list them in the standard. Then change the standard to list them in the correct places as needed.

D. Review of Stewardship List T 312 – ID

R 30 – UT Is Scott on the task force for R30? He is not but needs to be added so he can be aware of proposed changes from the task force. R 68 – TN T 245 – TN M 323 – IN R 35 - IN Any other volunteers? If there are no volunteers then the chair will assign standards to states as needed NCHRP project that had recommendations to make changes to M 323 and R 35 the information wasn’t presented. Chair will review and decide if it will be beneficial to share with the TS

E. Proposed New Standards – NONE!!!

F. NCHRP Issues – RNS on Plastics in Asphalt was the #1 Ranked RNS from the COMP. Discuss follow up research from 20-07 Task 406 BMD. Several (7) proposed RNS’s came as deliverables from Task 406. I submitted 3 of them through the State of MT this go ‘round because I forgot to bring them to the TS. Will submit them to the TS for consideration/ranking for the next research cycle. Since I doubt anyone would support all 7, perhaps a TS ballot for the members to rank their top 3?

FHWA proposed a RNS for Modification to binder with recycled plastic COMP proposed a RNS to include plastics as aggregate

G. Correspondence, Calls, Meetings - None

H. Proposed New Task Forces (Include list of volunteers to lead and/or join TF.)

I. New TS Ballots 1.

VII. Open Discussion

A. Is there a list of states and what they are stewards over? Chair doesn’t know of one. List of what standards TS 2d is over? Yes it is on the web site

VIII. Adjourn

TS Meeting Summary

Meeting Summary Items Approved by the TS for Ballot (Include reconfirmations.)

Standard Designation Summary of Changes Proposed Ballot Type

TS COMP CONCURRENT TS COMP CONCURRENT TS COMP CONCURRENT TS COMP CONCURRENT TS COMP CONCURRENT

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Meeting Summary TS COMP CONCURRENT TS COMP CONCURRENT TS COMP CONCURRENT TS COMP CONCURRENT TS COMP CONCURRENT TS COMP CONCURRENT New Task Forces Formed Task Force Name Summary of Task TF Member Names and (States) Research Proposals (Include number/title/states interested.) Other Action Items

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Ballot Detail

Ballot Name: Revisions to T 283

Ballot Manager: Ross Oak Metcalfe

Ballot Start Date: 4/3/2020

Ballot Due Date: 5/5/2020

Revisions to T 283

Item Number: 1

Description: Please indicate your approval or disproval of the suggested revisions to T 283 and provide any comments.

Decisions: Affirmative: 20 of 40 Negative: 1 of 40 No Vote: 16 of 40 (Was 19 – Remove OK, MA and ME - MEF)

Agency (Individual Name) Comments Decision

Heritage Research Group (Gerald Anton Huber) ([email protected])

Section 10.4.2, Note 4: 70 and 80 percent should be 70 to 80 percent

Florida Department of Transportation (Wayne Andrew Rilko) ([email protected])

We wish to retain the ability to test roadway cores per T 283. Done. Affirmative

Utah Department of Transportation (L. Scott Nussbaum) ([email protected])

UDOT isn't currently using the test but may again. We do believe the cure time adjustment may affect the test results.

Affirmative

Illinois Department of Transportation (Brian Pfeifer) ([email protected])

Section 2.2 - Determine if any states use ASTM D3387 for T283. If it’s not being used delete ASTM D3387. Add the following ASTM reference from 15.1: "ASTM. D979/D979M, Standard Practice for Sampling Bituminous Paving Mixtures." Section 5.8 - It is recommended to avoid changing the pan depth to a minimum of 1 in. The shallower depth creates more uniformity in the oven conditioning process. Sections 6 and 7 - There are several instances of "void content" and "percent air voids". It is recommended to maintain consistency and change all instances of "void content" to "air void content". Section 6.2 - Revise the first two sentences to read: "Compact specimens to 7.0 ± 0.5% air voids. This level of voids can be obtained by adjusting the mass of the mixtures or by adjusting the compactive effort (i.e. gyrations, blows or tamps) for the respective compaction procedure." Section 6.4 - Keep existing wording. These pan dimensions were set intentionally to have the mix samples spread thin to allow uniform aging. Section 7.3.1 - Revise the first two sentences to read: "Compact specimens to 7.0 ± 0.5% air voids. This level of voids can be obtained by adjusting the mass of the mixtures or by adjusting the compactive effort (i.e. gyrations, blows or tamps) for the respective compaction procedure." Section 9.4 - Equation 1: The result of the equation is shown as Va. However, the calculation is for Pa. It is recommended to change the equation to equal Pa. Section 15 - This is a second references section. It is recommended to move this reference to Section 2.

Affirmative

Nevada Department of Transportation (CHANGLIN PAN) ([email protected])

Section 6.9, 7.7, and 9.1 need a specific time frame before starting Section 9 for consistency purpose if 24 hours curing time got removed. Section 10.2 needs to include a language to specify when the dry subset can be tested for consistency purpose.

Affirmative

Massachusetts Department of Transportation (Clement Fung) ([email protected])

Section 9.4 Calculate the percentage of air voids (Va). Should be Va instead of Pa that matches the formula.

Affirmative

12 of 141

Ontario Ministry Of Transportation (Becca Lane) ([email protected])

Section 6.3 and 7.3.1: Replace "revolutions" with "gyrations" Section 6.9: Is the 24hrs requirement to help to stabilize the mix while it is cooling down? If removed, maybe put a requirement in terms of temperature of the specimen: "Allow compacted specimens to cool at normal room temperature until cool to the touch". Was any testing done with and without removing this 24hr requirement and if so, what was its effect especially for testing for dry specimens? Section 8.2: It should read "Obtain at least six cores for each" Section 9.1: The abbreviation “SGC" is not defined or mentioned anywhere in the document. SGC = Superpave Gyratory Compactor?

Affirmative

Missouri Department of Transportation (Brett Steven Trautman) ([email protected])

Affirmative vote with a comment. Missouri has no issues with the vast majority of the changes. We do have a concern with removing the requirement to store the specimens for 24 +/- 3 hours at room temperature. For over 15 years, Missouri has required QC and QA to perform T283 testing on material sampled from the field. We are not sure what the overall impact this will have on test results. To help answer this question, Missouri is conducting a small in-house study to determine the impact of not storing the specimens for 24 hours. For the Technical Subcommittee Ballot, Missouri will vote affirmative since we are unsure of the impact at this time. By the time these proposed changes are ready to be voted on by the full COMP we should have data available to make an inform decision at that time on this issue.

Affirmative

Kentucky Transportation Cabinet (Allen H Myers) ([email protected])

As discussed previously, this proposed revision removes the requirement to store the samples at room temperature for 24 hours. We are concerned about eliminating these sections without any supporting data.

Affirmative

Ohio Department of Transportation (Eric R Biehl) ([email protected])

Negative vote: I would like to see my comment below from Section 9.1 addressed. All other comments are general or editorial suggestions. Great work on reorganizing! Section 6.1.2: Any reason why they cannot make enough for two specimens? I know it's old language but seems odd. Section 6.2: You can adjust the height for SGC specimens too and would like to see this added. It's a lot easier than adjusting gyrations. Section 6.2: I would change "revolutions" to "gyrations" to be consistent with terminology used. Section 9.1: Measuring to an accuracy of only 3 mm when the accuracy of a 100 mm diameter specimen is 2.5 mm? There is no reason why we can't measure to the nearest mm. I would also like to see calipers (something other than a ruler) required but fine if it is not. Section 11.1.1: Rate has to be exactly 50 mm? Section 11.1.2: Just commenting that there is no reference to determine the degree of visual stripping as it relates to a rating of 5 to 0. This should be something that is considered in an update. Not this one, but a future one.

Negative

Date: 5/6/2020

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AASHTO Designation: T 283-

Technical Subcommittee: 2d, Proportioning of Asphalt–Aggregate Mixtures

Release: Group 3 (July)

American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001

14 (2018)

14 of 141

TS-2d T 283-1 AASHTO

Standard Method of Test for

AASHTO Designation: T 283-



1. SCOPE

1.1. This method covers preparation of specimens and the measurement of the change of diametral tensile strength resulting from the effects of water saturation and accelerated water conditioning, with a freeze–thaw cycle, of compacted asphalt mixtures. The results may be used to predict long-term stripping susceptibility of the asphalt mixture and evaluate liquid antistripping additives that are added to the asphalt binder or pulverulent solids, such as hydrated lime or portland cement, which are added to the mineral aggregate.

1.2. The values stated in SI units are to be regarded as the standard.

1.3. This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

2. REFERENCED DOCUMENTS

2.1. AASHTO Standards:

R 30, Mixture Conditioning of Hot Mix Asphalt (HMA)

R 47, Reducing Samples of Asphalt Mixtures to Testing Size

R 67, Sampling Asphalt Mixtures after Compaction (Obtaining Cores)

R 68, Preparation of Asphalt Mixtures by Means of the Marshall Apparatus

R 97, Sampling Asphalt Mixtures

T 166, Bulk Specific Gravity (Gmb) of Compacted Asphalt Mixtures Using Saturated Surface-Dry Specimens

T 167, Compressive Strength of Hot Mix Asphalt

T 209, Theoretical Maximum Specific Gravity (Gmm) and Density of Asphalt Mixtures

T 245, Resistance to Plastic Flow of Asphalt Mixtures Using Marshall Apparatus

T 247, Preparation of Test Specimens of Hot Mix Asphalt (HMA) by Means of California Kneading Compactor

T 312, Preparing and Determining the Density of Asphalt Mixture Specimens by Means of the Superpave Gyratory Compactor

14 (2018)

<#>T 269, Percent Air Voids in Compacted Dense and Open Asphalt Mixtures¶

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2.2. ASTM Standards:

D3387, Standard Test Method for Compaction and Shear Properties of Bituminous Mixtures by Means of the U.S. Corps of Engineers Gyratory Testing Machine (GTM)

3. SIGNIFICANCE AND USE

3.1. This method is intended to evaluate the effects of saturation and accelerated water conditioning, with a freeze–thaw cycle, of compacted asphalt mixtures. This method can be used to test: (a) asphalt mixtures in conjunction with mixture design testing (lab-mixed, lab-compacted); (b) asphalt mixtures produced at mixing plants (field-mixed, lab-compacted); and (c) asphalt mixture cores obtained from completed pavements of any age (field-mixed, field-compacted).

3.2. Numerical indices of retained indirect-tensile properties are obtained by comparing the properties of laboratory specimens subjected to moisture and freeze–thaw conditioning with the similar properties of dry specimens.

4. SUMMARY OF METHOD

4.1. Test specimens for each set of mix conditions, such as those prepared with untreated asphalt binder, asphalt binder treated with antistripping agent, or aggregate treated with lime, are prepared. Each set of specimens is divided into subsets. One subset is tested in dry condition for indirect-tensile strength. The other subset is subjected to vacuum saturation and a freeze cycle, followed by a warm-water soaking cycle, before being tested for indirect-tensile strength. Numerical indices of retained indirect-tensile strength properties are calculated from the test data obtained by the two subsets: dry and conditioned.

5. APPARATUS

5.1. Equipment for preparing and compacting specimens from one of the following: R 68, T 167, T 247, T 312, or ASTM D3387.

5.2. Equipment for determining the theoretical maximum specific gravity (Gmm) of the asphalt mixture from T 209.

5.3. Balance and water bath from T 166.

5.4. Water bath capable of maintaining a temperature of 60 ± 1°C (140 ± 2°F).

5.5. Freezer maintained at –18 ± 3°C (0 ± 5°F).

5.6. A supply of plastic film for wrapping specimens; heavy-duty, leakproof plastic bags to enclose the saturated specimens; and masking tape.

5.7. 10-mL graduated cylinder.

5.8. Pans having a surface area of 48 400 to 129 000 mm2 (75 to 200 in.2) in the bottom and at least a depth 25 mm (1 in.).

5.9. A tape, rule or calipers for measuring specimen thickness.

5.10. Forced-draft oven, thermostatically controlled, capable of maintaining any desired temperature setting from room temperature to 176°C (350°F) within ±3°C (±5°F).

<#>D3549/D3549M, Standard Test Method for Thickness or Height of Compacted Bituminous Paving Mixture Specimens ¶

As noted in the scope, t

T 245,

of approximately

Added measuring devices for speimen thickness.

16 of 141


5.11. Loading jack and ring dynamometer from T 245, or a mechanical or hydraulic testing machine from T 167, to provide a range of accurately controllable rates of vertical deformation, including 50 mm/min (2 in./min).

5.12. Steel loading strips with a concave surface having a radius of curvature equal to the nominal radius of the test specimen. For specimens 100 mm (4 in.) in diameter, the loading strips shall be 12.7 mm (0.5 in.) wide, and for specimens 150 mm (6 in.) in diameter, the loading strips shall be 19.05 mm (0.75 in.) wide. The length of the loading strips shall exceed the thickness of the specimens. The edges of the loading strips shall be rounded to the appropriate radius of curvature by grinding.

6. PREPARATION OF LABORATORY-MIXED, LABORATORY-COMPACTED SPECIMENS

6.1. Prepare mixture for at least six specimens for each test, half to be tested dry and the other half to be tested after partial saturation and moisture conditioning with a freeze–thaw cycle (Note 1).

Note 1—It is recommended that mixture for at least two additional specimens for each set be prepared. These specimens can then be used to establish compaction procedures for specimen void content as given in Section 6.2 and the vacuum saturation technique as given in Section 10.4.

6.1.1. If Gmm is unknown, prepare additional mixture according to R 30 Section 7.1, and determine the Gmm according to T 209.

6.1.2. Prepare mixtures in batches large enough to make at least three specimens or, alternatively, prepare a batch large enough to just make one specimen at a time. If preparing a multispecimen batch, split the batch into single-specimen quantities before placing in the oven.

6.2. Prepared compacted specimens shall be 7.0 ± 0.5 percent air voids. This level of voids can be obtained by adjusting the mass of the mixture; the number of blows in R 68; adjusting foot pressure, number of tamps, leveling load, or some combination in T 247; or adjusting the number of revolutions in T 312 or ASTM D3387. The effective adjustment must be determined experimentally for each mixture before compacting the specimens for each set. (Note 1).

6.3. Specimens 100 mm (4 in.) in diameter by 63.5 ± 2.5 mm (2.5 ± 0.1 in.) thick, or 150 mm (6 in.) in diameter by 95 ± 5 mm (3.75 ± 0.20 in.) thick are used. Specimens 150 mm (6 in.) in diameter by 95 ± 5 mm (3.75 ± 0.20 in.) thick should be used if aggregate larger than 25 mm (1 in.) is present in the mixture.

6.4. Place the mixture in a pan and cool at room temperature for 2 ± 0.5 h.

6.5. Place the cooled mixture in a 60 ± 3°C (140 ± 5°F) oven for 16 ± 1 h for curing. The pans should be placed on spacers to allow air circulation under the pan if the shelves are not perforated.

6.6. Place the mixture in an oven for 2 h ± 10 min at the compaction temperature ±3°C (5°F). Determine compaction temperature according to R 30.

6.7. Compact the specimens according to one of the following methods: R 68, T 167, T 247, T 312, or ASTM D3387 to 7.0 ± 0.5 percent air voids.

6.8. Remove the specimens from the molds (Note 2).

Note 2—Due to the elevated void content and potential instability of the specimens, ensure that each specimen is adequately cool and stable before removing from the mold.

Make

the

5

or 7.4

3

<#>Prepare mixtures in batches large enough to make at least three specimens or, alternatively, prepare a batch large enough to just make one specimen at a time. If preparing a multispecimen batch, split the batch into single-specimen quantities before placing in the oven.¶

<#>After mixing,

<#> shall be placed

<#>having a surface area of 48 400 to 129 000 mm2 (75 to 200 in.2) in the bottom and a depth of approximately 25 mm (1 in.)

<#>ed

Then the mixture shall be p

After curing, p

prior to compaction.

T 245,

. The mixture shall be compacted

This level of voids can be obtained by adjusting the number of blows in T 245; adjusting foot pressure, number of tamps, leveling load, or some combination in T 247; or adjusting the number of revolutions in T 312 or ASTM D3387. The exact procedure must be determined experimentally for each mixture before compacting the specimens for each set (Note 2).

prior to

al

17 of 141


6.9. Determine air voids according to Sections 9.3 and 9.4. The void content must be within 7.0 ± 0.5 percent.

7. PREPARATION OF FIELD-MIXED, LABORATORY-COMPACTED SPECIMENS

7.1. Obtain field-mixed asphalt mixture sample in accordance with R 97 of sufficient size to determine Gmm and make at least six specimens.

Note 3—It is recommended that mixture for at least two additional specimens for each set be obtained. These specimens can then be used to establish compaction procedures for specimen void content as given in Section 7.3.1 and the vacuum saturation technique as given in Section 10.4.

7.2. Determine Gmm by T 209.

7.3. Make at least six specimens for each test, half to be tested dry and the other half to be tested after partial saturation and moisture conditioning with a freeze–thaw cycle (Note 3).

7.3.1. Prepared compacted specimens shall be 7.0 ±0.5 percent air voids. This level of voids can be obtained by adjusting the mass of the mixture, the number of blows in R 68; adjusting foot pressure, number of tamps, leveling load, or some combination in T 247; or adjusting the number of revolutions in T 312 or ASTM D3387. The exact procedure must be determined experimentally for each mixture before compacting the specimens for each set. (Note 3)

7.4. Specimens 100 mm (4 in.) in diameter by 63.5 ± 2.5 mm (2.5 ± 0.1 in.) thick, or 150 mm (6 in.) in diameter by 95 ± 5 mm (3.75 ± 0.20 in.) thick are used. Specimens 150 mm (6 in.) in diameter by 95 ± 5 mm (3.75 ± 0.20 in.) thick should be used if aggregate larger than 25 mm (1 in.) is present in the mixture.

7.5. No loose-mix curing as described in Section 6.5 shall be performed on the field-mixed samples. After sampling, divide the sample to obtain the desired size in accordance with R 47. Next, place the mixture in an oven until it reaches the compaction temperature ±3°C (5°F). Then compact the specimen according to one of the following methods: R 68, T 167, T 247, T 312, or ASTM D3387 to 7.0 ± 0.5 percent air voids.

7.6. Remove the specimens from the molds (Note 2).

7.7. Determine air voids according to Sections 9.3 and 9.4. The void content must be within 7.0 ± 0.5 percent.

8. PREPARATION OF FIELD-MIXED, FIELD-COMPACTED SPECIMENS (CORES)

8.1. Select locations on the completed pavement to be sampled, and obtain cores according to R 67. When testing pavement layers with a thickness less than or equal to 63.5 mm (2.5 in.), use 100-mm (4-in.) diameter cores. Otherwise, use either 100-mm (4-in.) or 150-mm (6-in.) diameter cores.

8.2. Obtain at least six for each set of mix conditions. Additional cores may be required to determine Gmm by T 209.

8.3. Separate the core layers as necessary by sawing them or by other suitable means, and store the layers to be tested at room temperature until they are dry.

After removal from the molds, the specimens shall be stored for 24 ± 3 h at room temperature.

1

<#>Field-mixed asphalt mixtures shall be sampled in accordance with T 168.¶

<#>4

<#>, T 245

<#>The mixture shall be compacted to 7.0 ± 0.5 percent air voids. This level of voids can be obtained by adjusting the number of blows in T 245; adjusting foot pressure, number of tamps, leveling load, or some combination in T 247; or adjusting the number of revolutions in T 312 or ASTM D3387. The exact procedure must be determined experimentally for each mixture before compacting the specimens for each set (Note 2).

After removal from the molds, the specimens shall be stored for 24 ± 3 h at room temperature.

The number of cores shall be

18 of 141


8.4. No loose-mix curing (Section 6.5) or compacted-mix curing (Section 6.6) shall be performed on the field-mixed, field-compacted specimens (cores).

9. EVALUATION AND GROUPING OF SPECIMENS

9.1. Determine each specimen thickness (t) by measuring to 1mm (1/16 in.) in four locations around the specimen and averaging or, if the specimen is prepared by T 312, use the final height from the SGC.

9.2. Record each specimen diameter (D) as defined in Section 6.3, 7.4, or 8.1, as appropriate.

9.3. Determine each bulk specific gravity (Gmb) by Method A of T 166. Express the volume (E) of the specimens, or the saturated, surface-dry mass minus the mass in water, in cubic centimeters.

9.4. Calculate the percentage of air voids (Pa).

(1)

where:

Gmb = the bulk specific gravity; and;

Gmm = the theoretical maximum specific gravity.

9.5. Separate the specimens into two subsets, of at least three specimens each, so that the average air voids of the two subsets are approximately equal.

9.6. For those specimens to be subjected to vacuum saturation, a freeze cycle, and a warm-water soaking cycle, calculate the volume of air voids (Va) in cubic centimeters using the following equation:

100a

a

P EV = (1)

where:

Va = volume of air voids, cm3;

Pa = air voids, percent; and

E = volume of the specimen, cm3.

Note 4—A data sheet that is convenient for use with this test method is shown as Table 1.

10. PRECONDITIONING OF TEST SPECIMENS

10.1. One subset will be tested dry, and the other will be partially vacuum saturated, subjected to freezing, and soaked in warm water before testing.

10.2. Wrap the dry subset with plastic or place in a heavy-duty, leakproof plastic bag.

10.3. Place the specimens in a water bath with the conditioned subset according to section 10.4.11.

10.4. The other subset shall be conditioned as follows:

10.4.1. Place the specimen in the vacuum container supported a minimum of 25 mm (1 in.) above the container bottom by a perforated spacer. Fill the container with potable water at room temperature so that the specimens have at least 25 mm (1 in.) of water above their surface.

10.4.2. Saturate the specimen to 70 to 80 percent by applying a vacuum (Note 5).

4

<#>After curing, heating, or drying mixture samples or cores for the theoretical maximum specific gravity (Gmm) test as described in Sections 6.4 and 6.5, Section 7.4, or Section 8.2 as appropriate, determine the Gmm of those samples by T 209.¶

<#>3 mm (0.125 in.)

Replaced the 3mm reference with 1mm. Measurement is now consistent with ASTM 3549 requirments.

<#>in accordance with ASTM D3549/D3549M.

2

2

in accordance with T 269

3

The

will be stored at room temperature as described in Section 6.6 or Section 7.5, as appropriate. At the end of the curing period from Section 6.6 or 7.5, as appropriate, the specimens shall be wrapped

d

The

shall

then be placed

in a 25 ± 0.5°C (77 ± 1°F) water bath for 2 h ± 10 min with a minimum 25 mm (1 in.) of water above their surface. Then test the specimens as described in Section 11.

19 of 141


Note 5— Apply a vacuum for approximately 5 to 10 min. at approximately 13 to 67 kPa absolute pressure (10 to 26 in.Hg partial pressure). The time required for some specimens to achieve 70 and 80 percent may be less than 5 min. In addition, some specimens may require the use of an absolute pressure of greater than 67 kPa (26 in.Hg partial pressure) or less than 13 kPa (10 in.Hg partial pressure).

10.4.3. Remove the vacuum and leave the specimen submerged in water for a approximately 5 to 10 min.

10.4.4. Damp-dry the specimen by blotting it with a damp towel, and determine the surface-dry mass (B ) as quickly as possible (the entire operation is not to exceed 15 s). Any water that seeps from the specimen during the weighing operation is considered part of the saturated specimen. Each specimen shall be immersed and weighed individually.

Note 6— Terry cloth has been found to work well for an absorbent cloth. Damp is considered to be when no water can be wrung from the towel.

10.4.5. Calculate the volume of absorbed water (J ) in cubic centimeters by use of the following equation:

J = B – A (2)

where:

J = volume of absorbed water, cm3;

B = mass of the saturated, surface-dry specimen after partial vacuum saturation, g; and

A = mass of the dry specimen in air, g (Section 9.3).

10.4.6. Determine the degree of saturation (S ) by comparing the volume of absorbed water (J ) with the volume of air voids (Va) from Section 9.6 using the following equation:

100

a

JS

V

′′ = (3)

where:

S = degree of saturation, percent.

10.4.7. If the degree of saturation is between 70 and 80 percent, proceed to Section 10.4.9.

10.4.8. If the degree of saturation is less than 70 percent, repeat the procedure beginning with Section 10.4.1 using more vacuum and/or time. If the degree of saturation is more than 80 percent, the specimen has been damaged and must be discarded. In this case, repeat the procedure on the next specimen beginning with Section 10.4.1 using less vacuum and/or time.

10.4.9. Cover each of the vacuum-saturated specimens tightly with a plastic film (Saran Wrap® brand or equivalent). Place each wrapped specimen in a plastic bag containing 10 ± 0. 5 mL of water and seal the bag. Place the plastic bags containing the specimens in a freezer at a temperature of –18 ± 3°C (0 ± 5°F) for a minimum of 16 h. Remove the specimens from the freezer.

10.4.10. Place the specimens in a bath containing potable water at 60 ± 1°C (140 ± 2°F) for 24 ± 1 h. The specimens should have a minimum of 25 mm (1 in.) of water above their surface. As soon as possible after placement in the water bath, remove the plastic bag and film from each specimen.

10.4.11. After 24 ± 1 h in the 60 ± 1°C (140 ± 2°F) water bath, remove the specimens and place them and the dry subset in a water bath at 25 ± 0.5°C (77 ± 1°F) for 2 h ± 10 min. The specimens should have a minimum of 25 mm (1 in.) of water above their surface. It may be necessary to add ice to the water bath to prevent the water temperature from rising above 25°C (77°F). Not more than 15 min should be required for the water bath to reach 25 ± 0.5°C (77 ± 1°F).

4

the

correct degree of saturation (between

)

Apply a vacuum of 13 to 67 kPa absolute pressure (10 to 26 in.Hg partial pressure) for a short time (approximately 5 to 10 min).

short time (

)

Note 4—The time required for some specimens to achieve the correct degree of saturation (between 70 and 80 percent) may be less than 5 min. In addition, some specimens may require the use of an absolute pressure of greater than 67 kPa (26 in.Hg partial pressure) or less than 13 kPa (10 in.Hg partial pressure). ¶

Determine the mass of the saturated, surface-dry specimen after partial vacuum saturation (B ) by Method A of T 166.

4

3.7

3

3

Added language to tie section 10.3 to the conditioned subset. That way the 24 hr. is satisfied and now both the dry and conditioned subset will be in the same state for testing.

20 of 141


10.4.12 Remove the specimens from the water bath, and test them as described in Section 11.

11. TESTING

11.1. Determine the indirect-tensile strength of dry and conditioned specimens at 25 ± 0.5°C (77 ± 1°F).

11.1.1. Remove the specimen from 25 ± 0.5°C (77 ± 1°F) water bath, and determine the thickness (t ) according to Section 9.1. Place it between the steel loading strips and then place the specimen and loading strips between the two bearing plates in the testing machine. Care must be taken so that the load will be applied along the diameter of the specimen. Apply the load to the specimen, by means of the constant rate of movement of the testing machine head, at 50 mm/min (2 in./min).

11.1.2. Record the maximum compressive strength noted on the testing machine, and continue loading until a vertical crack appears. Remove the specimen from the machine, and pull it apart at the crack. Inspect the interior surface for evidence of cracked or broken aggregate; visually estimate the approximate degree of moisture damage on a scale from “0” to “5” (with “5” being the most stripped), and record the observations in Table 1.

Provided a step for the breaking reference. This was at the end of 10.4.11.

by ASTM D3549/D3549M

21 of 141


Table 1—Moisture Damage Laboratory Data Sheet (Nonmandatory Information)

Project

Additive Dosage Compaction Method Effort Date Tested By

Sample identification Diameter, mm (in.) D Thickness, mm (in.) t Dry mass in air, g A SSD mass, g B Mass in water, g C Volume (B – C), cm3 E Bulk specific gravity (A/E) Gmb Maximum specific gravity Gmm % air voids [100(Gmm – Gmb)/Gmm] Pa Volume of air voids (PaE/100), cm3 Va Load, N (lbf) P Saturated min @ kPa (psi) or mmHg (in.Hg)

Thickness, mm (in.) t

SSD mass, g B

Volume of absorbed water (B – A), cm3 J

% saturation (100J /Va) S

Load, N (lbf) P

Dry strength [2000P/ tD (2P/ tD)], kPa (psi) S1

Wet strength [2000P / t D (2P/ t D)], kPa (psi) S2

Visual moisture damage (0 to 5 rating)

Cracked/broken aggregate? TSR (S2/S1)

12. CALCULATIONS

12.1. Calculate the tensile strength as follows:

SI units:

2000t

PS

tD= (4)

where:

St = tensile strength, kPa;

P = maximum load, N;

t = specimen thickness, mm; and

D = specimen diameter, mm.

U.S. Customary units:

2t

PS

tD= (5)

where:

St = tensile strength, psi;

22 of 141


P = maximum load, lbf;

t = specimen thickness, in.; and

D = specimen diameter, in.

12.2. Express the numerical index of resistance of asphalt mixtures to the detrimental effect of water as the ratio of the original strength that is retained after the moisture and freeze–thaw conditioning. Calculate the tensile strength ratio to two decimal places as follows:

2

1

tensile strength ratio (TSR)S

S= (6)

where:

S1 = average tensile strength of the dry subset, kPa (psi); and

S2 = average tensile strength of the conditioned subset, kPa (psi).

13. REPORT

13.1. Report the following information:

13.1.1. Number of specimens in each subset;

13.1.2. Average air voids of each subset;

13.1.3. Tensile strength of each specimen in each subset;

13.1.4. Tensile strength ratio;

13.1.5. Results of visually estimated moisture damage observed when the specimen fractures; and

13.1.6. Results of observations of cracked or broken aggregate.

14. KEYWORDS

14.1. Accelerated water conditioning; diametral tensile strength; freeze–thaw cycle; liquid antistripping additives; long-term stripping; portland cement; pulverulent solids; water saturation.

15. REFERENCE

15.1. ASTM. D979/D979M, Standard Practice for Sampling Bituminous Paving Mixtures.

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Ballot Detail

Ballot Name: Updates to TP 124 and TP 133

Ballot Manager: Ross Oak Metcalfe

Ballot Start Date: 6/11/2020

Ballot Due Date: 7/2/2020

Updates to TP 124 and TP 133

Item Number: 1

Description: Revise TP 124 - The Illinois Department of Transportation has submitted a new appendix for long term aging with regard to the I-Fit test method. As a result, the reference to R 30 for long term aging has been removed while work on R 30 continues. This is the major change although there are other minor and editorial changes. Attached are a redline version of the document and a commentary explaining the changes.

Decisions: Affirmative: 33 of 37 Negative: 0 of 37 No Vote: 4 of 37


Florida Department of Transportation (Wayne Andrew Rilko) ([email protected])

X.2.2.3: Oven set at 95 ± 3°C (203 ± 5°F). X.2.2.4: 3 days ± 1 hour · NCAT determined that 5 days at 95Â°C was the most appropriate protocol to simulate 70,000 CDD of field aging. · A similar level of asphalt aging was achieved by loose mix aging for approximately 8 hours at 135Â°C. As a time-saving measure, the 8-hour, 135Â°C protocol was recommended as an alternative aging protocol to simulate 70,000 CDD of field aging. · Are we confident that 95 ± 3C (203 ± 5F) for 3 days ± 1 hour is the appropriate temperature and duration? · Although three days is less than five days, it is still a long time to wait for test results, especially if the same level of aging can be achieved in approximately eight hours at a higher temperature.

Affirmative

Pennsylvania Department of Transportation (Timothy L Ramirez) ([email protected])

Affirmative with comments: 1) On cover page and on page TP 124-1, revise AASHTO designation from "TP 124-18" to "TP 124-21". 2) In Section 9.1.1, Note 4, revise from "bricks" to "specimens" in three (3) locations (1st line, 3rd line, & 4th line) and from "brick" to "specimen" in one (1) location (5th line) for consistency with other sections of the standard which refer to "specimen" or "specimens". 3) In Section 9.1.2.1, 3rd from last line, suggest revising from "Cut each cylindrical specimen" to "Cut each cylindrical disc" for consistency of terminology used in the standard. 4) In Section 9.2, 1st line, revise from "directly on the discs" to "directly on each disc". 5) I am a little confused on whether the bulk specific gravity and percent air voids should be determined on the discs or on the semi-circular specimens (before the notch is cut) due to order and text contained in Sections 9.1.1, 9.1.2, and 9.3. Sections 9.1.1 and 9.1.2 indicate to prepare discs and then cut discs in half to form semi-circular test specimens. Then, Section 9.3 indicates to determine bulk specific gravity on the discs. If user were following this procedure in order, the discs would have already been cut in half to make semi-circular test specimens before they got to Section 9.3 to determine the bulk specific gravity on the discs. Consider moving text around somewhat to be in the proper order, especially if the bulk specific gravity and percent air voids are to be determined on each disc rather than on each semi-circular test specimen. 6) As follow-up to comment 5) above, at a minimum, consider revising existing

Affirmative

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Section 9.3 to read as follows: "9.3 Determining the Bulk Specific Gravity and Percent Air Voids--Determine the bulk specific gravity according to T 166 on each disc obtained from SGC specimens or pavement cores. Determine the percent air voids according to T 269. The air voids for each disc prepared from SGC specimens shall be 7.0 +/- 1.0 percent. The air voids for each disc prepared from pavement cores will not be subject to air void tolerances." This suggested revision will then require removal of some text from Sections 9.1.1 and 9.1.2 (i.e., reference to T 269 and the air voids criteria). 7) In Section X2.2.2, 1st line, revise from "notched face down" to "notched side face-down" for better readability. 8) In Section X2, regarding the long-term aging temperature, it's ten degrees Celsius higher than R 30. Based on the referenced R27-175 study, it is assumed that this conditioning procedure has been used by some labs. However, does this increased long-term aging temperature change the density of the sample (resulting in change to test results) and is there any concern of the samples getting distorted or falling apart at the higher temperature before they can be tested?


9.1.1, The wide range of air voids is inducing a wide range of FI in some mixes, it would be nice if the air voids range is tightened. 11.1, In a sealed bag in a water bath similar to T283 dry subset?

Affirmative

Tennessee Department of Transportation (Brian K. Egan) ([email protected])

Comment: Recommend replacing the word "bricks" with the word "specimens" in Note 4 of 9.1.1.

Affirmative

Ontario Ministry of Transportation (Anne Holt) ([email protected])

Comments: 5.1 - suggest adding Traffic Category to the list of factors affecting FI. 9.1.1 - The test is very sensitive to air voids. A 1.0% tolerance will introduce a large variation in the results. Although difficult, it is recommended to limit to a 0.5% tolerance. When we cut a disc into two halves, sometimes the air voids between the two halves is remarkably different. 9.1.1 - 6th line: "Similar" is not strong enough. Another term should be used to encourage making the discs as identical as possible. 9.1.2.1 - same comment as for 9.1.1 9.3 - 2.25 mm is very precise. It would be more achievable as 2.2 or 2.3 mm. Also, a range for the notch width would be preferred, for example: 1.0 to 2.2 mm. 14.1.5 - Recommend including notch width measurement on report. 15.3 - Is the precision estimate based on the revised notch width of 2.25 mm or is it based on the original notch width of 1.5 ± 0.5 mm? X.2.2.4 - It is recommended to specify 72 hours instead of 3 days. X2.2.6 - Not clear how to determine if the sample is cool. Suggest deleting the overnight sentence. 1 hr in front of fan should be sufficient. Or could include statement like "Allow specimens to cool at normal room temperature until cool to the touch".

Affirmative

Item Number: 2

Description: Move TP 124 to a Full Standard - With regard to Item 1, I would like to again seek the members input on moving TP 124 to a full standard. The provisional method was first published in 2016 however as of last year the method contains a precision and bias statement. It is also being evaluated in the NCHRP 9-57A ruggedness study. And while that report isnâ€™t due to be published until October, Illinois DOT has submitted a Technical Report from NCHRP 9-57A (available on the TRB website) and some internal DOT research, which are attached for your reference.


NO COMMENTS

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Item Number 3

Description: Revise TP 133 - TP 133 is also going through a ruggedness study and as such NC State has submitted significant revisions to TP 133. Attached are a redline version of the Provisional Method and a commentary document explaining the proposed revisions.



Pennsylvania Department of Transportation (Timothy L Ramirez) ([email protected])

Affirmative with comments: 1) In Section 3.7, there seems to be something missing from the remaining text "the peak-to-peak stress by the peak-to-peak axial strain". Should "by" be revised to "divided by"? 2) In Section 5.1, delete the existing 2nd sentence which starts "This property" as it seems redundant with the revised first sentence. 3) In Section 6.7, revise from "0.031-in. (0.8-mm) diameter" to "0.8-mm (0.031-in.) diameter" for consistency with standard in using SI units with inch-pound units in parenthesis. Also consider revising from "0.8-mm Diameter Carbon Steel Wire" to "Carbon Steel Wire". 4) Consider combining Sections 6.10 and 6.12 due to Note 4 and Note 5 being the same and Note 6 indicating same Epoxy Adhesive is satisfactory for affixing both loading platens and gauge points to the test specimen. 5) In Section 9.1, the sentence is missing something. I think it needs the period removed after the word "percent" and the word "in" added between "percent" and "accordance". 6) In Section 9.2, consider revising first line if comment 4) above is implemented so as not to include "for gauge points". 7) In Section 9.4.1, 1st line, revise from "that was in contact" to "that will be in contact" since both new and used platens need cleaning unless this step is not needed for new platens. If this step is not needed for new platens, then it should be revised to clarify that this step is only needed for used loading platens. 8) In Section 9.6, Note 8, replace "has" with "is" or add "been found" after "has". 9) In Section 9.8, suggest revising from "spread evenly between the loading platens" to "spread one half on the top loading platen and one half on the bottom loading platen". 10) In Section 9.10, revise from "gluing jig" to "gluing apparatus" for consistency with terminology. 11) In Section 9.14, the first two sentences should remain combined or if kept as separate sentences, revise beginning of 2nd sentence from "Taking" to "Take". 12) In Section 11.1.3, 1st line, revise from "center- mounted" to "center-mounted" (i.e., delete space after the hyphen). 13) In Section 11.1.9, revise from "0.8-mm wire" to "0.8-mm carbon steel wire for consistency with terminology in Section 6.7. 14) In Section 11.1.10, revise from "Figure 7to" to "Figure 7 to". 15) In Figure 6 caption, suggest revising from "for example an 80-mm diameter" to "for example 80-mm diameter". 16) In Figure 7 caption, suggest revising from "for example a 130-mm diameter" to "for example 130-mm diameter". 17) In Section 11.1.14, revise from "1/3rd" to simply "1/3" in three locations [2nd line (1X) & 3rd line (2X)], to make similar to the latter part of the same section. 18) In Section 11.2, should this be revised from "Dynamic Modulus Fingerprint Test" to "Fingerprint Dynamic Modulus Test" to coincide with revision to add Section 3.10? 19) In Section 11.2.1, 1st line, similarly to comment 18) above, should "dynamic modulus fingerprint test" be revised to "fingerprint dynamic modulus test"?

Affirmative

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20) In Section 12.3.4, the 3rd and 5th "where" parameters and their definitions are not properly vertically aligned with each other. 21) In Section 13.2.4, add space between bottom of Table 6 and the Table 7 title. 22) In Section 13.6.7, 1st line, revise from "adjustment , K" to "adjustment, K" (i.e., delete space after "adjustment" and before the comma). 23) In Section 13.6.7, 2nd line, suggest deleting hyphen at end of 2nd sentence. 24) In Section 14.2.2, at end, add "and". 25) In Section 14.2.3, at end, revise from "(DR); and" to "(DR).".


9.11, It would be nice to mention that the gauge studs are not in the same plane as the loading platen screws openings. It is somewhat discussed in section 9.2 but might be appropriate to include it here if the gauge points are glued first. X3, remove hyphens in Section X3.1 and X3.2 to be consistent

Affirmative

Missouri Department of Transportation (Brett Steven Trautman) ([email protected])

Affirmative vote with three editorial comments: 1) It appears previous Sections 5.1 and 5.2 were combined to form one section. Section 5.1 was deleted while Section 5.2 was changed to Section 5.1. When the changes are accepted, not sure if the section number will be located at the beginning of the section. 2) It appears previous Sections 11.1.7 and 11.1.8 were combined to form one section. Section 11.1.7 was deleted while Section 11.1.8 was changed to Section11.1.15. When the changes are accepted, not sure if the section number will be located at the beginning of the section. 3) It appears previous Section 12.32 and previous Note 10 were combined to form one section. Section 12.32 was deleted while Note 10 was changed to Section 13.6.10. When the changes are accepted, not sure if the section number will be located at the beginning of the section.

Affirmative

Tennessee Department of Transportation (Brian K. Egan) ([email protected])

Comments: - Figure 3 and section 6.4 replace deformation sensors to LVDTs - Section 6.2. Recommend adding "It is recommended to use the dummy specimen made with an identical mixture to a specimen to be tested. If not possible, recommend using identical NMAS to a specimen to be tested."

Affirmative

Date: 7/3/2020

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July 22, 2020

Comments Addressed for AASHTO TP 124-181, Release: Group 3 (August)

• Maryland DOT 1. Since it is added to TP 124, no problem in deleting it from R 30. We are okay

with this change. No response necessary.

• Florida DOT 1. From Appendix X.2, subsections X.2.2.3. (Regarding Oven set at 95 ± 3˚C (203

± 5˚F)) and X.2.2.4. (Regarding 3 days ± 1 hour), respectively. NCAT determined that 5 days at 95°C was the most appropriate protocol to simulate 70,000 CDD of field aging. A similar level of asphalt aging was achieved by loose mix aging for approximately 8 hours at 135°C. As a time-saving measure, the 8-hour, 135°C protocol was recommended as an alternative aging protocol to simulate 70,000 CDD of field aging. Are we confident that 95 ± 3˚C (203 ± 5˚F) for 3 days ± 1 hour is the appropriate temperature and duration? Although three days is less than five days, it is still a long time to wait for test results, especially if the same level of aging can be achieved in approximately eight hours at a higher temperature.

IDOT funded a University of Illinois study (Illinois Center for Transportation (ICT) Study R27-175) between 2017 and 2019 to evaluate long-term aging (LTA) properties of Illinois HMA surface mixtures and to develop an appropriate LTA protocol using the I-FIT1. This study considered aging in a pressurized aging vessel (PAV), a vacuum oven, and a forced-draft oven using loose mix, gyratory cylinders, and prepared I-FIT specimens. PAV and vacuum oven aging were removed from consideration early in the research study because they were not readily available in all District materials labs in addition to other concerns. Researchers tested a total of 12 plant-produced mixtures and 7 lab-produced mixtures. All mixtures were compacted in the lab using a gyratory compactor. Data showed that loose mix aging reduced I-FIT Flexibility Index (FI) more quickly than prepared I-FIT specimen aging at the same oven time duration and temperature. However, loose mix aging necessitated stirring at consistent time intervals and may need companion Gmm samples to determine prepared specimen air voids after compaction and cutting. Prepared specimen aging required more oven conditioning time, but did not require the testing lab to verify air voids after conditioning. Prepared specimen aging temperature was limited because SMA specimens were deteriorating at 110°C. Several key points were identified in the study prior to the development of the LTA protocol. First, IDOT requires HMA performance testing in both mix design and mix production.

1 Al-Qadi, I. L., H. Ozer, Z. Zhu, P. Singhvi, U. Mohamed Ali, M. Sawalha, A. Francisco, E. Luque, J. Garcia Mainier, and T. Zehr. 2019. Development of Long-Term Aging Protocol for Implementation of the Illinois Flexibility Index Test (I-FIT), FHWA ICT-19-009. Illinois Center for Transportation, Rantoul, IL.

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Second, HMA Contractors are required to compact enough gyratory cylinders to complete Hamburg Wheel, unaged (re-heated) I-FIT, and LTA I-FIT (surface mixtures only) procedures in IDOT District materials labs. Third, IDOT randomly chooses the gyratory cylinder(s) to be cut and prepared for each performance test. The researchers and technical research panel for the project determined that aging fully prepared I-FIT specimens in a forced draft oven was the most appropriate approach. Prepared specimens would not require air void determination after aging and companion Gmm samples. In addition, if prepared specimens did not meet dimension criteria, new back-up specimens could be compacted and prepared immediately before aging without needing to age more loose mix and then compact and prepare back-up specimens. A 95°C LTA forced draft oven temperature was chosen by the researchers as the maximum temperature based on the previously mentioned issue with SMA at 110°C. A 1 day at 95°C aging duration was not close enough to the point where FI began to decay at a reduced rate. The 3 day at 95°C aging duration was closer to that point for Illinois mixtures. Additionally, the 3 day at 95°C aging duration FI results were not significantly different from the AASHTO R30 LTA protocol FI results. Therefore, a LTA protocol of 3 days at 95°C in a forced draft oven was chosen and inserted as Appendix X.2 in AASHTO TP124. A separate research study currently being completed through the National Road Research Alliance (NRRA) of ten Minnesota HMA mixtures included unaged (reheated) and LTA I-FIT evaluations. IDOT completed testing using the I-FIT procedure. The 3 day at 95°C prepared specimen LTA protocol and a 6 hour at 135°C loose mix LTA protocol (proposed by NRRA) were used. The average FI reduction (compared to the unaged result) using the 3 day at 95°C LTA protocol was 59% and the average FI reduction using the 6 hour at 135°C LTA protocol was 40%. Although 8 hours at 135°C loose mix aging was not completed as part of this effort, it is assumed that 2 additional hours of loose mix aging at 135°C would increase the average FI reduction percentage to a value closer to 59%. IDOT believes that the 3 day at 95°C prepared specimen LTA protocol is appropriate for specimens tested in the I-FIT procedure. However, please note that this is based on the R27-175 study evaluating Illinois mixtures. It is recognized that the NCAT LTA method of loose mix aging 8 hours at 135°C is a published method that other specifying agencies could employ. Therefore, to be fair to other specifying agencies with different aggregate and asphalt binder sources as well as environmental conditions, Section 10 of AASHTO TP124 was developed in its current form.

• Pennsylvania DOT 1. On cover page and on page TP 124-1, revise AASHTO designation from "TP

124-18" to "TP 124-21".

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AASHTO Designation: TP 124-181 changed to TP 124-211 2. In Section 9.1.1, Note 4, revise from "bricks" to "specimens" in three (3)

locations (1st line, 3rd line, & 4th line) and from "brick" to "specimen" in one (1) location (5th line) for consistency with other sections of the standard which refer to "specimen" or "specimens".

The word “brick(s)” was changed to the word “specimen(s)” in four (4) locations to be consistent with the rest of the document.

3. In Section 9.1.2.1, 3rd from last line, suggest revising from "Cut each cylindrical specimen" to "Cut each cylindrical disc" for consistency of terminology used in the standard.

This sentence was moved to form new Section 9.1.2.4. and was revised to read “Cut Semi-Circular Test Specimens – Cut each cylindrical disc in half to produce two dimensionally equivalent semi-circular test specimens,”

4. In Section 9.2, 1st line, revise from "directly on the discs" to "directly on each disc".

Section 9.2. was renumbered to be Section 9.1.2.2. and was modified to read “Determining the Bulk Specific Gravity—Determine the bulk specific gravity directly on each disc obtained from pavement cores according to T 166.”

5. I am a little confused on whether the bulk specific gravity and percent air voids should be determined on the discs or on the semi-circular specimens (before the notch is cut) due to order and text contained in Sections 9.1.1, 9.1.2, and 9.3. Sections 9.1.1 and 9.1.2 indicate to prepare discs and then cut discs in half to form semi-circular test specimens. Then, Section 9.3 indicates to determine bulk specific gravity on the discs. If user were following this procedure in order, the discs would have already been cut in half to make semi-circular test specimens before they got to Section 9.3 to determine the bulk specific gravity on the discs. Consider moving text around somewhat to be in the proper order, especially if the bulk specific gravity and percent air voids are to be determined on each disc rather than on each semi-circular test specimen.

Section 9.1.1. pertains only to SGC Specimens. Section 9.1.2. Pavement Cores pertains only to Pavement Cores and was reorganized and modified somewhat to indicate more clearly the proper order of operations and includes Section 9.1.2.1. Pavement Core Specimen Preparation, Section 9.1.2.2. Determining the Bulk Specific Gravity, Section 9.1.2.3. Determining the Air Voids, and Section 9.1.2.4. Cut Semi-Circular Test Specimens. Then, Section 9.3. Notch Cutting and Section 9.4. Determining Specimen Dimensions were re-numbered to be Sections 9.2. and 9.3. and pertain to both SGC and Pavement Core Specimens.

6. As follow-up to comment 5) above, at a minimum, consider revising existing Section 9.3 to read as follows: "9.3 Determining the Bulk Specific Gravity and Percent Air Voids--Determine the bulk specific gravity according to T 166 on each disc obtained from SGC specimens or pavement cores. Determine the percent air voids according to T 269. The air voids for each disc prepared from SGC specimens shall be 7.0 +/- 1.0 percent. The air voids for each disc prepared from pavement cores will not be subject to air void tolerances." This suggested revision will then require removal of some text from Sections 9.1.1 and 9.1.2 (i.e., reference to T 269 and the air voids criteria).

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Refer to response in Comment #5 above. 7. In Section X2.2.2, 1st line, revise from "notched face down" to "notched side

face-down" for better readability. Section X.2.2.2. Revised to read “Place the four (4) test specimens

notched side facing down,…” 8. In Section X2, regarding the long-term aging temperature, it's ten degrees

Celsius higher than R 30. Based on the referenced R27-175 study, it is assumed that this conditioning procedure has been used by some labs. However, does this increased long-term aging temperature change the density of the sample (resulting in change to test results) and is there any concern of the samples getting distorted or falling apart at the higher temperature before they can be tested?

The oven temperature of 95˚C that was determined in the ICT R27-175 study has been used widely by IDOT and Contractor labs since that study’s completion and is planned to be fully implemented in 2021. It was also used for long-term aging in IDOT’s most recent Round Robin Uniformity study. In the R27-175 study, one of the questions was whether to long-term age loose mix or to long-term age prepared test specimens. The decision was made to long-term age the prepared test specimens which allowed the density to be determined on the un-aged specimen prior to aging. As a result, if a change in the Maximum Specific Gravity occurred during the long-term aging process, and the specimen air voids changed to be out of tolerance, the process of fabricating and aging specimens did not have to start all over, saving significant time. Several different test temperatures were evaluated including 75˚C, 85˚C, 95˚C, and 110˚C. There were cases at 110˚C where some specimens deformed from a few of the Illinois mixtures that were tested. (See Section 4.4 of the study report (Footnote 1 on pg. 1 of this document).) Specimens from mixtures tested at 95˚C were stable and the shape remained intact.

• Nevada DOT 1. 9.1.1, The wide range of air voids is inducing a wide range of FI in some mixes,

it would be nice if the air voids range is tightened. IDOT has relatively large datasets from 2018-2020 I-FIT round robins

demonstrating that the 7.0 ± 1.0% air voids range is appropriate. At least 30 labs were included in each of the three round robins with at least 8 specimens tested per lab. In 2020, each participating lab was asked to test 8 unaged (re-heated plant-produced mixture) specimens and 8 LTA (3 days at 95°C) specimens. As stated previously, there is little correlation between I-FIT FI and air voids within the 6.0 to 8.0% range in these multi-laboratory round robins. Please note that the previous sentence is based on testing Illinois mixtures. Also, note that IDOT did not focus on extreme air void cases outside the 7.0 ± 1.0% range in these round robin studies. It is agreed that air voids outside the 7.0 ± 1.0% will likely show differences in FI due to the post peak slope parameter. If data from

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mixtures in other states/provinces is showing more sensitivity to air voids, IDOT would be interested in viewing and discussing those data results.

2. 11.1, In a sealed bag in a water bath similar to T283 dry subset? The R27-1282 and the R27-175 ICT studies both followed Illinois

modified AASHTO T283 which does not place the specimen in Saran Wrap and a plastic bag before submerging in the water bath. A water bath, an oven and an environmental chamber were each evaluated in the study to bring the temperature of the specimen to approximately 25˚C. No significant difference was apparent between conditioning in the three methods.

• Tennessee DOT 1. Comment: Recommend to replace the word "bricks" with the word "specimens"

in Note 4 of 9.1.1. See response to Pennsylvania Comment #2.

• Ontario MOT 1. 5.1. suggest adding Traffic Category to the list of factors affecting FI

Traffic levels determine Ndesign. Dr. Imad Al-Qadi, the PI of both the R27-128 and the R27-175 studies, was asked about this question. He responded that “When you change the aggregate gradation or binder, you change the Ndesign to maintain 4% Air Voids. So, a change in the mix design will affect FI”.

2. 9.1.1. The test is very sensitive to air voids. A 1.0% tolerance will introduce a large variation in the results. Although difficult, it is recommended to limit to a 0.5% tolerance. When we cut a disc into two halves, sometimes the air voids between the two halves is remarkably different.

See response to Nevada Comment #1. 3. 9.1.1. 6th line: "Similar" is not strong enough. Another term should be used to

encourage making the discs as identical as possible. The word “similar” was changed to the words “dimensionally

equivalent”. The word “similar” is vague, but “identical” is not achievable with asphalt mix. “Dimensionally equivalent” explains better what is being required.

4. 9.1.2.1. same comment as for 9.1.1. See response above for Section 9.1.1.

5. 9.3. 2.25 mm is very precise. It would be more achievable as 2.2 or 2.3 mm. Also, a range for the notch width would be preferred, for example: 1.0 to 2.2 mm.

The notch width tolerance is proposed to be increased to 2.25mm. A commercially available, off-the-shelf tile saw blade is the most practical means of cutting the notch. The most common, and stable, tile saw blade has a metal core that typically is rated at 0.060-in (1.524-mm) thick (although this measurement often varies somewhat). Diamond is bonded to the edge of the metal core as a cutting material. The diamond adds a small, but measurable additional thickness. Blades with a core thickness of 0.050-in (1.27-

2 Al-Qadi, I. L., H. Ozer, J. Lambros, A. El Khatib, P. Singhvi, T. Khan, and B. Doll. 2015. Testing Protocols to Ensure Performance of High Asphalt Binder Replacement Mixes Using RAP and RAS, FHWA ICT-15-07. Illinois Center for Transportation, Rantoul, IL.

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mm) are also available, but tend to wobble somewhat, especially if the tile saw is used to cut the disc into two semicircular test specimens as well as to cut the notch. The initial notch width as written in the ICT R27-128 study report was 1.5 ± 0.05mm. This was adjusted slightly to 1.5 ± 0.10mm. In practice, a 1.5 mm notch width is very difficult, almost impossible, to achieve, considering variations in a new, off-the-shelf saw blade, slight amounts of blade wobble in use, specimens being fed through the blade at an angle slightly different than perpendicular, over tightening the saw motor arbor nut on the blade, etc. even with operating technicians exercising appropriate attention to quality and following the procedure. The purpose of the notch is to define where the crack initiates. For that, specifying a minimum notch width is not necessary and for practical purposes only being too wide is only of concern when the notch is so wide that the crack initiates in (for instance) the front right side of the notch and on the left side of the back of the specimen. This effectively could increase the ligament area of the cracked face by a slight amount. However, the ligament area is considered as a factor in the fracture energy calculation in Equation 4 in the specification. A notch width of 2.25 mm (2 ¼ mm) was chosen because it is achievable practically and is significantly thinner than a 0.125 in. core (3.175 mm) saw blade used on typical core saws available in most labs.

6. 14.1.5. Recommend including notch width measurement on report. The notch width requirement was placed in the specification to

guide users toward an appropriate saw blade width. The final measurement of saw blade width is not used in calculations of fracture energy or flexibility index. As a result, , this may not be a critical measurement to report.

7. 15.3. Is the precision estimate based on the revised notch width of 2.25 mm or is it based on the original notch width of 1.5 ± 0.5 mm?

The CBM 2017, 2018, & 2019 multi-laboratory Round Robin Uniformity Studies were used to calculate the Precision Statement. All specimens were prepared according to IL Test Procedure 405 (Used until AASHTO TP 124 was adopted) and then IL modified AASHTO TP 124. IL mod TP 124 was updated on 12/1/2018 to require a notch width of 2.25 mm. Since the beginning of testing using the I-FIT procedure, the CBM has been aware of the difficulties achieving a notch width that met the 1.5 mm specification. The CBM fabricated part of the specimens used in the 2017 Round Robin Study and all the specimens in the 2019 Round Robin Study. The participants cut the notch for the remainder of the specimens in the 2017 Round Robin and all the specimens in the 2018 Round Robin.

8. X.2.2.4. It is recommended to specify 72 hours instead of 3 days. Appendix Section X.2.2.4 was changed to read “Leave the

specimens (undisturbed) in the oven at this temperature for 72 hours ± 1 hour” instead of “…3 days ± 1 hour.”

9. X2.2.6. Not clear how to determine if the sample is cool. Suggest deleting the overnight sentence. 1 hr in front of fan should be sufficient. Or could include

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statement like "Allow specimens to cool at normal room temperature until cool to the touch".

The IDOT CBM HMA lab looked at the cooling time of I-FIT prepared semi-circular test specimens.: Two “dummy” specimens were used. A hole was drilled to the center of each specimen, a temperature probe was inserted, and held in place with liquid asphalt. The specimens were placed in a 95˚C oven until the center of the specimen reached 95˚C. The specimens were removed from the oven. One was placed in front of a fan and the other was placed away from the fan. The time required for the temperature to reach “room temperature” was recorded. This was done multiple times. The temperature consistently came down to room temperature in under an hour for the specimen placed in front of a fan. For the specimens not placed in front of the fan, the temperature took somewhat longer to come to room temperature, but still was not significantly longer than an hour. Since almost all labs have fans, cooling overnight was selected primarily for those labs that removed the specimens from the oven at the end of the day and chose to not run the fan for the entire night. A couple of reasons the specimens need to be cooled to room temperature is to keep the specimens from deforming when handled and to allow the “barrier” to be removed without tearing or damaging the specimen. This is easily accomplished with either method. Also, the sample will be placed in the 25˚C (77˚F) water bath for 2 hours before being tested in the I-FIT machine, so the test temperature will be determined by the water bath or environmental chamber.

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AASHTO Designation: TP 124-211

Technical Section: 2d, Bituminous Materials

Release: Group 3 (August)


181

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TS-2d TP 124-1 AASHTO



Technical Section: 2d, Bituminous Materials

Release: Group 3 (August)

1. SCOPE

1.1. This test method covers the determination of Mode I (tensile opening mode during crack propagation) cracking resistance properties of asphalt mixtures at intermediate test temperatures. Specimens are tested in the semicircular bend geometry, which is a half disc with a notch parallel to the direction of load application. The data analysis procedure associated with this test determines the fracture energy (Gf) and post peak slope (m) of the load–load line displacement (LLD) curve. These parameters are used to develop a Flexibility Index (FI) to predict the fracture resistance of an asphalt mixture at intermediate temperatures. The FI can be used as part of the asphalt mixture approval process.

1.2. These procedures apply to test specimens having a nominal maximum aggregate size (NMAS) of 19 mm or less. Lab compacted and pavement core specimens can be tested according to this test procedure. A thickness correction factor will need to be developed and applied for pavement cores tested at a thickness less than 45 mm.

1.3. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish and follow appropriate health and safety practices and determine the applicability of regulatory limitations prior to use.



R 67, Sampling Asphalt Mixtures after Compaction (Obtaining Cores)



T 269, Percent Air Voids in Compacted Dense and Open Asphalt Mixtures

T 283, Resistance of Compacted Asphalt Mixtures to Moisture-Induced Damage


TP 105, Determining the Fracture Energy of Asphalt Mixtures using Semicircular Bend Geometry (SCB)

18

<#>R 30, Mixture Conditioning of Hot Mix Asphalt (HMA)¶

Hot Mix Asphalt (HMA)

Hot Mix Asphalt (HMA)

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2.2. ASTM Standards:

D8, Standard Terminology Relating to Materials for Roads and Pavements

D3549/D3549M, Standard Test Method for Thickness or Height of Compacted Bituminous Paving Mixture Specimens

2.3. Other Publications:

Al-Qadi, I. L., H. Ozer, J. Lambros, A. El Khatib, P. Singhvi, T. Khan, and B. Doll. 2015. Testing Protocols to Ensure Performance of High Asphalt Binder Replacement Mixes Using RAP and RAS, FHWA ICT-15-07. Illinois Center for Transportation, Rantoul, IL.

Doll. B., H. Ozer, J. Rivera-Perez, J. Lambros, and I. L. Al-Qadi. 2016. Investigation of Viscoelastic Fracture Fields in Asphalt Mixtures using Digital Image Correlation. International Journal of Fracture, Vol. 205, No. 1, pp. 37–56.

Ozer, H., I. L. Al-Qadi, J. Lambros, A. El-Khatib, P. Singhvi, and B. Doll. 2016a. Development of the Fracture-Based Flexibility Index for Asphalt Concrete Cracking Potential Using Modified Semi-Circle Bending Test Parameters. Construction and Building Materials, Vol. 115, pp. 390–401.

Ozer, H., and P. Singhvi, T. Khan, J. Rivera, I. L. Al-Qadi. 2016b. Fracture Characterization of Asphalt Mixtures with RAP and RAS Using the Illinois Semi-Circular Bending Test Method and Flexibility Index. Transportation Research Record, Transportation Research Board, National Research Council, Washington, DC, Vol. 2575, pp. 130–137.

Ozer, H., I. L. Al-Qadi, P. Singhvi, J. Bausano, R. Carvalho, X. Li, and N. Gibson. 2017. Assessment of Asphalt Mixture Performance Tests to Predict Fatigue Cracking in an Accelerated Pavement Testing Trial. International Journal of Pavement Engineering, Special Issue for Cracking in Flexible Pavements and Asphalt Mixtures: Theories to Modeling, and Testing to Mitigation.

RILEM Technical Committee 50-FMC. 1985. “Determination of the Fracture Energy of Mortar and Concrete by Means of Three-Point Bend Tests on Notched Beams.” Materials and Structures, Springer Netherlands for International Union of Laboratories and Experts in Construction Materials, Systems and Structures (RILEM), Dordrecht, The Netherlands, No. 106, July–August 1985, pp. 285–290.

3. TERMINOLOGY

3.1. Definitions:

3.1.1. critical displacement, u1—displacement at the intersection of the post-peak slope with the displacement-axis.

3.1.2. displacement at peak load, u0—recorded displacement at peak load.

3.1.3. final displacement, ufinal—recorded displacement at the 0.1 kN cut-off load.

3.1.4. flexibility index, FI—index intended to characterize the cracking resistance of asphalt mixture, calculated by multiplying the ratio of fracture energy to post-peak slope by a constant multiplier.

3.1.5. fracture energy, Gf—energy required to create a unit surface area of a crack.

3.1.6. ligament area, Arealig—cross-sectional area of specimen through which the crack propagates, calculated by multiplying ligament width (test specimen thickness) and ligament length.

3.1.7. linear variable displacement transducer (LVDT)—sensor device for measuring linear displacement.

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3.1.8. load line displacement (LLD)—displacement measured in the direction of the load application.

3.1.9. post-peak slope, m—slope at the first inflection point of the load–LLD curve after the peak.

3.1.10. semicircular bend (SCB) geometry—a half disc with a notch parallel to the direction of load application.

3.1.11. work of fracture (Wf)—calculated as the area under the load–LLD curve.


4.1. A Superpave Gyratory Compactor (SGC) compacted asphalt mixture specimen or an asphalt pavement core is trimmed and cut in half to create a semicircular test specimen. A notch is sawn in the flat side of the semicircular specimen opposite the curved edge. The specimen is conditioned and maintained through testing at 25 ± 0.5 C. The specimen is positioned in the fixture with the notched side down centered on two rollers. A load is applied along the vertical radius of the specimen and the load and load line displacement (LLD) are measured during the entire duration of the test. The load is applied such that a constant LLD rate of 50 mm/min is obtained and maintained for the duration of the test. The I-FIT fixture and I-FIT specimen geometry for an SGC laboratory compacted specimen are shown in Figure 1.

4.2. Fracture energy (Gf), post-peak slope (m), displacement at peak load (u0), critical displacement (u1), and a flexibility index (FI) are calculated from the load and LLD results.

Figure 1—I-FIT SGC Laboratory Compacted Specimen Configuration (dimensions in millimeters)


5.1. The I FIT is used to determine fracture resistance parameters of an asphalt mixture at an intermediate temperature (Al-Qadi et al. (2015), Ozer et al. (2016a), Ozer et al. (2016b)). From the fracture parameters of Gf and m obtained, the FI of an asphalt mixture is calculated. The FI provides a means to identify brittle mixtures that may be prone to premature cracking. The range

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for an acceptable FI will vary according to local environmental conditions, application of mixture, nominal maximum aggregate size (NMAS), asphalt binder content, asphalt binder performance grade (PG), air voids, and expectation of service life, etc. (Al-Qadi et al. (2015), Ozer et al. (2016a), Ozer et al. (2016b), Ozer et al. (2017)).

5.2. The calculated FI indicates an asphalt mixture’s overall capacity to resist cracking related damage (Al-Qadi et al. (2015)). Generally, a mixture with higher FI can resist crack propagation for longer time duration under tensile stress. The FI should not be directly used in structural design and analysis of pavements. FI values, obtained using this procedure, are used in ranking the cracking resistance of alternative mixtures for a given layer in a structural design. The Gf parameter is dependent on specimen size, loading time, and is temperature dependent. Fracture mechanisms for viscoelastic materials are influenced by crack front viscoelasticity and bulk material (far from the crack front) viscoelasticity. Total calculated Gf from this test includes the amount of energy dissipated by crack propagation, viscoelastic mechanisms away from the crack front, and other inelastic irreversible processes (frictional and damage processes at the loading support points) (Doll et al., 2016).

5.3. Gf is one of the parameters used to calculate the FI, which is further used to predict AC mixture fracture potential. It also represents the main parameter input in more complex analyses based on a theoretical crack (cohesive zone) model. In order to be used as part of a cohesive zone model, fracture energy as calculated from the experiment shall be corrected to determine energy associated with crack propagation only. A correction factor may be used to eliminate other sources of inelastic energy contributing to the total fracture energy calculated directly from the experiment.

5.4. This test method and FI can be used to rank the cracking resistance of asphalt mixtures containing various asphalt binders, modifiers of asphalt binders, aggregate blends, fibers, and recycled materials.

5.5. The specimens can be readily obtained from SGC compacted cylinders or from pavement cores with a diameter of 150 mm.

6. APPARATUS

6.1. Testing Machine—An I-FIT system consists of a closed-loop axial loading device, a load measuring device, a bend test fixture, specimen deformation measurement devices, and a control and data acquisition system. A constant displacement-rate device, such as a closed loop, feedback-controlled servo-hydraulic load frame, shall be used.

Note 1—An electromechanical, screw-driven machine may be used if results are comparable to a closed loop, feedback-controlled servo-hydraulic load frame.

6.1.1. Axial Loading Device—The loading device shall be capable of delivering loads in compression with a maximum resolution of 10 N and a capacity of at least 10 kN.

6.1.2. Bend Test Fixture—The fixture is composed of a loading head, a steel base plate, and two steel rollers with a nominal diameter (D) of 25 mm. The tip of the loading head has a contact curvature with a radius of 12.5 ± 0.05 mm. The horizontal loading head shall pivot relative to the vertical loading axis to conform to slight specimen variations. The length of the two roller supports in Figure 2 and Figure 3 shall be a minimum of 65 mm. Illustrations of the loading and supports are shown in Figures 2 and 3.

6.1.2.1. Method A—Typically two steel rollers with a nominal diameter of 25 mm are mounted on bearings through their axis of rotation and attached to the steel base plate with brackets. One of the steel rollers may pivot on an axis perpendicular to the axis of loading to conform to slight

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specimen variations. A distance of 120 ± 0.1 mm between the two steel rollers is maintained throughout the test.

6.1.2.2. Method B—An alternate fixture design uses two steel rollers with a nominal diameter of 25 mm that each rotate in a U-shaped roller support steel block. The initial roller position is fixed by springs and backstops that establish the initial test span dimension of 120 ± 0.1 mm. The support rollers are allowed to rotate away from the backstops during the test; but remain in contact with the sample.

6.1.3. Internal Displacement Measuring Device—The displacement measurement can be performed using the machine’s stroke (position) transducer if the resolution of the stroke is sufficient (0.01 mm or lower). The fracture test displacement data may be corrected for system compliance, loading-pin penetration and specimen compression by performing a calibration of the testing system.

6.1.4. External Displacement Measuring Device—If an internal displacement measuring device does not exist or has insufficient precision, an externally applied displacement measurement device such as a linear variable differential transducer (LVDT) accurate to 0.01 mm can be used (Figure 2 and Figure 3).

6.1.5. Control and Data Acquisition System—Time and load, and LLD (using external and/or internal displacement measurement device) are recorded. The control data acquisition system is required to apply a constant LLD rate at a precision of 50 ± 1 mm/min and collect data at a minimum sampling frequency of 20 Hz in order to obtain a smooth load–LLD curve.

Note 2—The use of two LLD transducers 180 degrees from one another and on each side of a test specimen may be used. In this approach, an average LLD value is computed to control the test. Controlling the test using an average LLD value may reduce test variability.

6.1.6. Saw—Laboratory saw capable of cutting asphalt specimens; must be capable of cutting the notch described in Figure 1.

6.1.7. Conditioning Chamber—Water bath or environmental chamber capable of maintaining specimen temperature as described in Section 11.1.

6.1.8. Measuring Device—Caliper or ruler accurate to ±0.1 mm for specimen thickness and area measurement.

0

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Figure 2—Method A—Isometric, Cross-Section, and Elevation of the I-FIT Fixture (dimension in millimeters)

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Figure 3—Method B—Isometric, Cross-Section, and Elevation of the I-FIT Fixture (dimension in millimeters)

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7. HAZARDS

7.1. Standard laboratory caution should be used in handling, compacting, and fabricating asphalt mixtures test specimens in accordance with T 312 and when using a saw for cutting specimens.

8. CALIBRATION AND STANDARDIZATION

8.1. A water bath as used in AASHTO T 283 or an environmental chamber will be used to maintain the specimen at a constant and uniform temperature.

8.2. Verify the calibration of all measurement components (such as load cells and LVDTs) of the testing system.

8.3. If any of the verifications yield data that does not comply with the accuracy specified, correct the problem prior to proceeding with testing. Appropriate action may include maintenance of system components, calibration of system components (using an independent calibration agency, service by the manufacturer, or in-house resources), or replacement of the system components.

9. PREPARATION OF TEST SPECIMENS AND PRELIMINARY DETERMINATIONS

9.1. Test Specimen Size—For mixtures with a NMAS of 19 mm or less, prepare the test specimens from a lab compacted SGC specimen or from pavement cores. If laboratory compacted SGC specimens are used, the final I-FIT specimens shall have smooth parallel faces with a thickness of 50 ± 1 mm and a diameter of 150 ± 1 mm (see Figure 4). If pavement cores are used, refer to Figure 1 for the notch width and notch length dimensions and tolerances. The final pavement core I-FIT specimen dimensions shall be 150 ± 8 mm in diameter with smooth parallel faces 25 to 50 ± 1 mm thick depending on available field layer thickness.

Note 3—A typical laboratory saw for mixture specimen preparation can be used to obtain cylindrical discs with smooth parallel surfaces. A tile saw is recommended for cutting the 15 ± 1 mm notch in the individual I-FIT specimens. Diamond-impregnated cutting faces and water cooling are recommended to minimize damage to the specimen. When cutting the I-FIT specimens into semi-circular halves, it is recommended not to push the two halves against each other because it may create an uneven base surface of the test specimen that can affect the I-FIT results.

9.1.1. SGC Specimens—Prepare one laboratory SGC specimen according to T 312 in the SGC with the compaction height a minimum of 160 mm ± 1 mm. From the middle of each 160 mm ± 1 mm tall specimen, obtain two cylindrical 50 ± 1 mm thick discs with smooth, parallel faces by saw cutting (see Figure 4). For laboratory compacted specimens, the bulk specific gravity and the air voids shall be determined for each of the two circular discs according to T 269. The air voids for each disc shall be 7.0 ± 1.0 percent. Cut each disc into two dimensionally equivalent halves resulting in four individual I-FIT specimens. A minimum of three individual test specimens are required for one I-FIT result. Note 4— The height of the gyratory compacted specimens should be 160 ± 1 mm to achieve a target 7.0 ± 1.0% air voids in each disc (see Figure 4). If a lab does not have the capability to compact 160 ± 1 mm tall gyratory specimens, then two 115 ± 1 mm tall gyratory specimens may be compacted and used instead to replace each 160 ± 1 mm tall gyratory specimen. A 50 ± 1 mm thick disc will be cut from the middle of each gyratory specimen, which will result in four individual I-FIT specimens (see Figure 4).

identical

bricks

individual semi-circular test specimen

bricks

bricks

brick

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OR

Figure 4—Specimen preparation from 160 mm or 115 mm Tall SGC specimens

9.1.2. Pavement Cores—Obtain pavement cores in accordance with R 67. Obtain one 150 mm diameter pavement core if the lift thickness is greater than or equal to 100 mm, or two 150 mm diameter pavement cores if the lift thickness is less than 100 mm.

9.1.2.1. Pavement Core Specimen Preparation—Prepare four replicate I-FIT specimens using pavement cores obtained from a pavement lift, with smooth, parallel surfaces that conform to the height and diameter requirements specified herein. To preserve and maximize core thickness, the as-compacted face shall be utilized as well as a sawed face. The thickness of test specimens in most cases for pavement cores may vary from 25 to 50 ± 1 mm. If the lift thickness is less than 50 ± 1 mm, test specimens should be prepared as thick as possible but in no case be less than two times the nominal maximum aggregate size of the mixture or 25 ± 1 mm, whichever is greater. If lift thickness is greater than 50 ± 1 mm, a 50 ± 1 mm disc shall be prepared as specified in Section 9.1. Cores from pavements with lifts greater than 75 ± 1 mm may be cut to provide two cylindrical specimens of equal thickness. In the upper-most pavement layer when cored, the as-compacted face will remain intact and one cut will be made to produce a disc at least two times the nominal maximum aggregate size of the mixture or 25 ± 1 mm, whichever is greater. In all subsequent discs cut from that pavement core, two sawed faces may be used to produce smooth, parallel surfaces.

9.1.2.2. Determining the Bulk Specific Gravity—Determine the bulk specific gravity directly on each disc obtained from pavement cores according to T 166.

9.1.2.3. Determining the Air Voids—The air void contents of each disc shall be determined according to T 269. Pavement cores will not be subject to air void content tolerances.

9.1.2.4. Cut Semi-Circular Test Specimens—Cut each cylindrical disc in half to produce two dimensionally equivalent semicircular test specimens.

9.2. Notch Cutting—Cut a notch along the axis of symmetry of each individual semicircular specimen to a depth of 15 ± 1 mm and 2.25 mm in width (see Figure 1).

The air void contents of each disc shall be determined according to T 269. Pavement cores will not be subject to air void content tolerances. Cut each cylindrical specimen exactly in half to produce two identical, semicircular specimens. Each disc of the pavement core shall have parallel smooth faces.

the

s

SGC specimens or

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Note 5—If the notch terminates in an aggregate particle 9.5 mm or larger on both faces of the specimen, the specimen shall be discarded.

9.3. Determining Specimen Dimensions—Measure the notch depth on both faces of the specimen and record the average value to the nearest 0.5 mm. Measure and record the ligament length (see Figure 1) and thickness of each specimen. The ligament length may be measured directly on both faces of the specimen with the average value recorded, or the ligament length may be measured indirectly by subtracting the notch depth from the entire width (radius) of the specimen on both faces of the specimen and averaging the two measurements. Measure the specimen thickness approximately 19.0 mm on either side of the notch and on the curved edge directly across from the notch. Average the three measurements and record as the average thickness to the nearest 0.1 mm.

10. LONG-TERM AGING

10.1. Perform a long-term aging procedure on I-FIT specimens as defined by the specifying agency. Note 6—The I-FIT specimen long-term aging procedure in Appendix X2 may be used.

11. TEST PROCEDURE

11.1. Conditioning—Test specimens shall be conditioned in a water bath or an environmental chamber at 25 ± 0.5 °C for 2 h ± 10 min.

11.1.1. Test Temperature Control—Immediately after removing the test specimen from the conditioning water bath or environmental chamber, complete positioning and testing of the I-FIT specimen within 5 ± 1 min to ensure that the specimen temperature is maintained.

11.2. Position Specimen—Position the test specimen in the test fixture on the rollers so that it is centered in both the “x” and the “y” directions and so that the vertical axis of loading is aligned to pass from the center of the top radius of the specimen through the middle of the notch.

11.3. Contact Load—First, impose a contact load of 0.1 ± 0.01 kN in stroke control with a loading rate of 0.05 kN/s.

11.3.1. Record Contact Load—Record the contact load to ensure it is achieved.

11.3.2. Loading—After the contact load of 0.1 kN is reached, the test is conducted using LLD control at a rate of 50 mm/min. The test stops when the load drops below 0.1 kN.

11.3.3. Repeat Sections 11.1 through 11.3.2 for each test specimen.

12. PARAMETERS

12.1. Determining Work of Fracture (Wf)—The work of fracture is calculated as the area under the load–LLD curve (see Figure 5). If the test is stopped prior to reaching 0.1 kN, the remainder of the load–LLD curve should be produced by extrapolation techniques.

The area under the load–LLD curve is calculated using a numerical integration technique. In order to apply the numerical integration, raw load-displacement data shall be divided into two curves described by an appropriate fitting equation. A polynomial equation with a degree of six is sufficient for the curve prior to peak load (Equation 1). An exponential-based function (Equation

Note 6-If testing for the effects of long-term aging (LTA) is to be conducted, the procedure specified in AASHTO R30 should be used.¶

0

0

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2) is used for the post-peak load portion of the curve. Then, analytical integration shall be applied to calculate the area under each curve (Equation 3).

For displacements (u) prior to the peak load (Pmax):

6 5 4 3 2 11 1 2 3 4 5 6 7( )P u c u c u c u c u c u c u c= × + × + × + × + × + × + (1)

where:

ci = polynomial coefficients.

For displacements (u) after the peak load (Pmax) to the cut-off displacement (ufinal): d

4

2

2

( ) expn

ii

ii

u eP u d

f

= −= − (2)

where:

d, e, f = polynomial coefficients, n is the number of exponential terms.

Work of fracture can be analytically or numerically calculated using the integral equation below and boundaries of displacement:

( ) ( )0 final

0

1 20

u u

fu

W P u du P u du= + (3)

where:

u0 = displacement at the peak load;

ufinal = displacement at the 0.1 kN cut-off load.

Note 7—Due to the relative difference between the compliance of testing frame and specimen, displacement recorded may vary. A correction factor may need to be considered to correct recorded displacements when applicable.

Figure 5—Recorded Load (P)–Load Line Displacement (u) Curve

Peak Load

Slope at Inflection Point (m)

CriticalDisplacement(u1)

Final Displacement(u

final)

Displacement, u (mm)

Load

,P (

kN)

0 1 2 3 4 5 60

1

2

3

4

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12.2. Fracture Energy (Gf)—The fracture energy Gf, determined as per the RILEM TC 50-FMC (1985) approach, is calculated by dividing the work of fracture (the area under the load–LLD curve; see Figure 5) by the ligament area (the product of the ligament length and the thickness of the specimen) of the I-FIT specimen prior to testing:

6

lig

10Area

ff

WG = × (4)

where:

Gf = fracture energy (Joules/m2); Wf = work of fracture (Joules); P = load (kN); u = load line displacement (mm); Arealig = ligament area = (r – a) × t, (mm2); r = specimen radius (mm); a = notch length (mm); t = specimen thickness (mm).

Note 8—Gf is a size dependent property. This specification does not aim at calculating size independent Gf. Therefore, cracking resistance of asphalt mixtures quantified with Gf may vary when the notch length to radius ratio changes.

12.3. Determining Post-Peak Slope (m)—The inflection point is determined on the load–LLD curve (Figure 5) after the peak load. The slope of the tangential curve drawn at the inflection point represents post-peak slope.

12.4. Determining Displacement at Peak Load (u0)—The displacement when peak load is reached.

12.5. Determining Critical Displacement (u1)—Intersection of the tangential post-peak slope with the displacement axis yields the critical displacement value. A straight line is drawn connecting the inflection point and displacement axis with a slope m.

12.6. Flexibility Index (FI)—FI can be calculated from the parameters obtained using the load–LLD curve (Al-Qadi et al. (2015), Ozer et al. (2016a), Ozer et al. (2016b)). The factor A is used for unit conversion and scaling. A is equal to 0.01. Complete details of the analysis procedure are provided in Appendix X1.

fGFI A

m= × (5)

where:

|m| = absolute value of post-peak load slope m (kN/mm).

13. CORRECTION FACTORS

13.1. Correction Factors for Flexibility Index—Flexibility index correction factors for pavement core specimen thickness and differences between field and lab compaction may be needed. A thickness correction factor may be applied for pavement cores tested at thickness less than 45 mm. The correction factors may require local calibration to consider locally available materials and mixture design requirements.

14. REPORT

14.1. Report the following information:

14.1.1. Bulk specific gravity of each specimen tested, to the nearest 0.001;

A

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14.1.2. Air void content of each disc, to the nearest 0.1 percent;

14.1.3. The number of cut faces for each specimen tested, if pavement cores were used.

14.1.4. Average thickness t and average ligament length of each specimen tested, to the nearest 0.1 mm;

14.1.5. Initial notch length a, to the nearest 0.5 mm;

14.1.6. Average and coefficient of variation (COV) of peak load, to the nearest 0.1 kN;

14.1.7. Average and COV of recorded time at peak load, to the nearest 0.1 s;

14.1.8. Average and COV of load-line displacement at the peak load (u0), to the nearest 0.1 mm;

14.1.9. Average and COV of critical displacement (u1), to the nearest 0.1 mm;

14.1.10. Average and COV of post-peak slope (m), to the nearest 0.1 kN/mm;

14.1.11. Average and COV of fracture energy Gf, to the nearest 1 J/m2; and

14.1.12. Average and COV of flexibility index to the nearest 0.1.

15. PRECISION AND BIAS

15.1. Precision:

15.2. Single-Operator Precision – The single-operator coefficient of variation of flexibility index has been found to be 27.1%. Therefore, results of two properly conducted tests by the same operator on the same material are not expected to differ from each other by more than 75.9% of their average.

15.3. Multi-laboratory Precision – The multi-laboratory coefficient of variation of flexibility index has been found to be 34.1%. Therefore, results of two properly conducted tests by two different laboratories on specimens of the same material are not expected to differ from each other by more than 95.5% of their average.

Table 1 – Precision Estimatesa

Material Average FI

Components of Variance Variances

Single Operator Between Laboratory Single Operator Multi-Laboratory 2017 5.2 2.36 0.49 2.36 2.85

2018 23.1 36.85 7.64 36.85 44.49

2019 9.6 5.90 9.55 5.90 15.44

Material Average FI

Standard Deviations Coefficients of Variation (%)

Single Operator Multi-Laboratory Single Operator Multi-Laboratory 2017 5.2 1.54 1.69 29.6 32.5

2018 23.1 6.07 6.67 26.3 28.9

2019 9.6 2.43 3.93 25.3 41.0 a Based on a multi-laboratory study of state departments of transportation, private, and academic laboratories in 2017, 2018, and 2019.

Three materials (All 9.5 mm NMAS mixtures) with varying contents of RAP were used (a different mixture was used each year). Approximately 12 specimens were tested per material on at least 30 devices per year.

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15.4. Bias—No information can be presented on the bias of the procedure because no material having an accepted reference value is available.

16. KEYWORDS

16.1. Asphalt mixture; flexibility index; Illinois flexibility index test (I-FIT); fracture energy; semicircular bend (SCB); stiffness; work of fracture.

APPENDIXES

X1. CALCULATIONS

X1.1. SCOPE:

X1.1.1. This appendix presents the framework and algorithms used to process the load–LLD curve and to compute the critical variables such as fracture energy, slope (after the crack begins propagating), and flexibility index. The algorithm consists of the following steps:

X1.1.1.1. Preprocessing the raw load–LLD curve; X1.1.1.2. Pre-peak calculations; and X1.1.1.3. Post-peak calculations.

X1.2. PREPROCESSING:

X1.2.1. The algorithm starts with preprocessing the raw test output file containing the load and displacement data. The first step of pre-processing is to trim the tail of the curve. The data points whose load values are smaller than 0.1 kN are removed. Because the load–LLD curve exhibits different characteristics before and after the peak load, the trimmed load–LLD curve is divided into two parts: pre-peak and post-peak. To do this, the peak load at which maximum load value is reached is identified. The values of the load–LLD curve before the peak load are assigned to the pre-peak segment; the remaining data are assigned to the post-peak segment. The calculations required for pre-peak and post-peak segments are explained in Sections X1.3 and X1.4.

X1.3. PRE-PEAK CALCULATIONS:

X1.3.1. The following steps are completed to process the pre-peak segment of the load–LLD curve:

X1.3.1.1. The beginning (ui, Pi) and end (u0, Pmax) coordinates of the load–LLD curve are captured. X1.3.1.2. A polynomial equation with a degree of six is fitted to the pre-peak segment of the load–LLD

curve (Equation X1.1).

6 5 4 3 2 11 1 2 3 4 5 6 7( )P u c u c u c u c u c u c u c= × + × + × + × + × + × + (X1.1)

where:

ci = polynomial coefficients.

X1.3.1.3. A new set of data is generated with equal displacement increments using the polynomial function bounded by the beginning and end points found in Section X1.3.1.1. The increments used to divide the data are found by dividing the displacement at the peak load by 1000. A new

X1

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displacement vector (upre) is generated from ui to u0 with calculated increments. The new loading vector is computed by substituting the value of the displacement vector in Equation X1.1. The purpose of generating a dataset with higher resolution is to increase the accuracy of the numerical integration described in Section X1.3.1.4.

X1.3.1.4. Numerical integration is applied to calculate area under the pre-peak segment of the load–LLD curve. The integral for area calculation is given in Equation X1.2. A trapezoidal integration technique is used for the numerical integration of Equation X1.2. When analytical integration tools are available, analytical integration is recommended to improve accuracy.

0

10

(pre-peak) ( )u

fW P u du= (X1.2)

X1.3.1.5. When the load–LLD curve starts with a residual load at zero displacement, the curve needs to be extrapolated to modify the area calculated in the previous step. In such cases, the curve is linearly extrapolated to the displacement coordinate where the load is zero. The displacement at the zero load (ur) is found. The area under the extrapolated segment is added to calculate total pre-peak area X1. Numerical integration is applied to find the residual area shown by the additional term in Equation X1.3. The second part of the sum comes from the additional area of extrapolation.

0

10

(pre-peak) ( ) 0.5u

f r rW P u du u P= + × × (X1.3)

where:

Pr = residual load at zero displacement; and

ur = calculated displacement at zero load.

X1.4. POST-PEAK CALCULATIONS:

X1.4.1. An algorithm was developed to process the post-peak segment of the load–LLD curve to calculate area under the curve as well as the inflection point and slope at the inflection point. Explanations of each step are given in Sections X1.4.1.1 through X1.4.1.3.

X1.4.1.1. The beginning (u0, P0) and end (uf, Pf) coordinates of the post-peak load–LLD curve are captured (see Figure X1.1). The raw data records are stored in two vectors as upost = {u0, …, uf} and Ppost = {P0,…, Pf}.

X1.4.1.2. In this step, candidate lower bounds for parameter f in Equation X1.4 are initialized and kept in a vector. This parameter can govern the first derivative of the post-peak segment resulting in abnormal slope values. For example, if a lower bound is not defined for this parameter, it may go to zero, which creates a spike-like, spurious slope. On the other hand, if the bound is defined too high, accuracy of the fitted curve may be compromised. Therefore, candidate values for the lower bounds for this parameter were found to be f bounds = {0.9, 0.7, 0.5, 0.3, 0.1, 0.05, 0.01, 0.005, 0.001}. The optimum value is found iteratively looping over the values initialized in the f bounds. The order of the values should be descending.

4

2

2

( ) expn

ii

ii

u eP u d

f

= −= − (X1.4)

where:

d, e, f = polynomial coefficients, and n = number of exponential terms.

50 of 141


X1.4.1.3. All model parameters in Equation X1.4 are regularized by setting lower and upper bounds for each of them. Upper and lower bounds for each parameter except f are initialized as 10 and –10, respectively. Because of the limitations of the regression function used in MATLAB (the function called “fit”), the regularization had to be conducted in a heuristic way.

X1.4.1.3.1. A regression function that input upost and Ppost are developed by fitting the Gaussian function (Equation X1.4) to the post-peak segment of the data bounded by the limits defined in Section X1.4.1. The number of Gaussian terms is selected as four. Then, the inflection points at which the second derivative of the fitted equation becomes zero are extracted, and the first derivatives indicating the slopes (mi) are computed at the extracted inflection points (ui).

X1.4.1.3.2. It is possible that the second derivative of the fitted equation P2(u) may not have any roots (i.e., there is no inflection point; hence, no slope can be found). If P2(u) does not have any roots, the next value in the vector fbounds should be selected before proceeding with the remaining steps. If a root or roots of P2(u) exists, proceed to the next step.

X1.4.1.3.3. At each inflection point found, draw the tangential slope by extrapolating a line intersecting the displacement axis, as shown in Figure X1.1. The first derivative value at the inflection is defined as the post-peak slope (m) as shown below.

2

inf

( )P um

u u u

∂=

∂ =

(X1.5)

Figure X1.1—Demonstration of Pre-Peak and Post-Peak Segments

X1.4.1.3.4. It is common that the fitted equation may produce more than one slope when there is more than one root found in the previous step. There is only one slope considered consistent with the definition of the tests; the remaining slopes are spurious and need to be eliminated. To find the most representative slope and eliminate the unrealistic slope(s), three visual based criteria are implemented. The criteria, grading, and elimination processes are as follows:

Criterion 1—Incremental displacement values (un) are generated with equal increments between u0 and ui. A linear slope equation, S(u), is described by using the slope (see Equation

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X1.5) and passing through the inflection point (ui). The mean value of difference between slope equation and post-peak load–LLD curve is calculated using Equation X1.6.

( ) ( )[ ]211

M

n nn

S u P u

CM

=

−

= (X1.6)

where:

M = number of displacement values such that (u0 < un < ui). Equal sizes of increments are used to create M-times displacement values (un). M may vary depending on the length between u0 and ui;

S(un) = value of slope equation calculated at u = un; and

P2(un) = value of post-peak load–LLD curve calculated at u = un.

Figure X1.2—Checking Mean Difference for Criterion 1

Criterion 2—Incremental displacement values (un) are generated with equal increments between u0 and ut. The ut is found by taking 30 percent of Pi = P2(ui) (load corresponding to the inflection point) (see Figure X1.3). The same linear slope equation, S(u), is used as in Criterion 1. The mean value of difference between slope equation and post-peak load–LLD curve is calculated using Equation X1.7.

( ) ( )[ ]

M

uSuPM

1nnn2

=

−

=C2 (X1.7)

where: M = number of displacement values such that (u0 < un < ut). Equal sizes of increments are used

to create M-times displacement values (un). M may vary depending on the length between u0 and ut;

S(un) = value of slope equation calculated at u = un;

P2(un) = value of post-peak load–LLD curve calculated at u = un.

The ideal slope line should be perfectly tangential or remain below the fitted curve. Therefore, the slope lines with negative means are eliminated. The grading scheme for this criterion is similar to the previous one. If more than one slope remains after elimination, slopes are

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ranked in an ascending order according to the mean difference (C2). The slope with lowest mean difference is ranked highest.

Figure X1.3—Checking Mean Difference for Criterion 2

Criterion 3—The value of this criterion is –x coordinate of inflections points (i.e., ui). If there are multiple candidates for slope line, they are ranked with an ascending order according to their ui. For example, slopes found at smaller inflection points ranked higher than the slope found at the tail part of the curve.

X1.4.1.3.5. If at least one realistic slope is found, and the R2 of the fit is higher than 0.997, the fit is accepted and the loop is stopped. In that case, the framework jumps to Section X1.4.4 to calculate fracture energy and report the representative slopes along with other required test outcomes. Otherwise, the loop continues—that is, the next value from fbound is selected to modify the lower bound for the parameter f. Sections X1.4.1.3.1 through X1.4.1.3.5 are repeated until a representative slope and satisfactory R2 is found.

X1.4.1.4. Using the satisfactory fit, P2(u), and representative inflection point and post-peak slope values (m), the test parameters required in the report section of the specification are calculated.

X1.4.1.4.1. Representative slope is reported as the one with the highest score from the grading process (Section X1.4.1.3.4).

X1.4.1.4.2. Similar to the pre-peak area calculation, a new displacement vector between up and ufinal by an increment of 0.005 is generated. Then corresponding load values are calculated by feeding this generated displacement vector to the fitted regression functions. The purpose of generating new sets of data with increased resolution is to increase the accuracy of the numerical integration in the next step.

X1.4.1.4.3. A trapezoidal numerical integration technique (Figure X1.2) is employed for the integral shown in Equation X1.8 to calculate the area under the post-peak segment of the curve.

final

02(post-peak) ( )

u

fu

W P u du= (X1.8)

X1.4.1.4.4. The total area under the load–LLD curve is found by adding the pre-peak and post-peak areas. Then the work of fracture is calculated using the Equation X1.9.

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(post-peak) (pre-peak) f f fW W W= + (X1.9)

X1.4.1.4.5. Total energy and slope are inputted to Equations X1.10a and X1.10b to compute fracture energy and flexibility index.

6

lig

10Area

ff

WG = × (X1.10a)

fGF I A

m= × (X1.10b)

X2. LONG-TERM AGING PROCEDURE

X2.1. SCOPE:

X2.1.1. This appendix includes and summarizes the findings of the R27-175 study conducted by the Illinois Center for Transportation through the Illinois Department of Transportation to evaluate the long-term aging effects on hot mix asphalt surface mixtures using the Illinois Flexibility Index Test and to develop a corresponding long-term-aging protocol.

X2.2. PROCEDURE:

X2.2.1. Prepare surface mixture test specimens according to Section 9. X2.2.2. Place the four (4) test specimens, notched side facing down, on a tray (pan), with a “barrier”

between the test specimens and the tray (parchment paper, a non-stick cooking mat, heavy duty aluminum foil, etc. are examples of a “barrier”).

X2.2.3. Place the tray with the specimens in a pre-heated force-draft oven set at 95 ± 3˚C (203 ± 5˚F). X2.2.4. Leave the specimens (undisturbed) in the oven at this temperature for 72 hours ± 1 hour. X2.2.5. Remove the entire tray from the oven and place in front of a cooling fan at room temperature for at

least one hour. X2.2.6. If the specimen is not cooled in front of a fan, allow the specimens to cool at room temperature

overnight. X2.2.7. Remove the specimen from the “barrier”. X2.2.8. After the specimens have cooled and the “barrier” has been removed, proceed to Section 11.

1 This provisional standard was first published in 2016. 2 Appendix X1 written by Hasan Ozer, Osman Erman Gungor, and Imad Al-Qadi, Illinois Center for Transportation, University of Illinois at Urbana-Champaign. 3 Appendix X2 is based on the findings from the following study: Al-Qadi, I. L., H. Ozer, Z. Zhu, P. Singhvi, U. Mohamed Ali, M. Sawalha, A. Francisco, E. Luque, J. Garcia Mainier, and T. Zehr. 2019. Development of Long-Term Aging Protocol for Implementation of the Illinois Flexibility Index Test (I-FIT), FHWA ICT-19-009. Illinois Center for Transportation, Rantoul, IL.

fGFI As

m= ×

¶

e

¶

¶

3

days

¶

¶

¶

¶

¶

54 of 141

Responses to Comments on AASHTO TP 133

Comments from Timothy L. Ramirez of the Pennsylvania Department of Transportation

1. In Section 3.7, there seems to be something missing from the remaining text "the peak-to-peak stress by the peak-to-peak axial strain". Should "by" be revised to "divided by"? Response: Yes, this has been corrected in the revised standard.

2. In Section 5.1, delete the existing 2nd sentence which starts "This property" as it seems redundant with the revised first sentence. Response: The sentence has been deleted.

3. In Section 6.7, revise from "0.031-in. (0.8-mm) diameter" to "0.8-mm (0.031-in.) diameter" for consistency with standard in using SI units with inch-pound units in parenthesis. Also consider revising from "0.8-mm Diameter Carbon Steel Wire" to "Carbon Steel Wire". Response: The standard was revised accordingly.

4. Consider combining Sections 6.10 and 6.12 due to Note 4 and Note 5 being the same and Note 6 indicating same Epoxy Adhesive is satisfactory for affixing both loading platens and gauge points to the test specimen. Response: The suggested change was made.

5. In Section 9.1, the sentence is missing something. I think it needs the period removed after the word "percent" and the word "in" added between "percent" and "accordance". Response: The sentence has been revised to state: “Prepare at least three test specimens at the target air void content ±0.5 percent in accordance with PP 99.”

6. In Section 9.2, consider revising first line if comment 4) above is implemented so as not to include "for gauge points". Response: The suggested change was made.

7. In Section 9.4.1, 1st line, revise from "that was in contact" to "that will be in contact" since both new and used platens need cleaning unless this step is not needed for new platens. If this step is not needed for new platens, then it should be revised to clarify that this step is only needed for used loading platens. Response: The wording was changed to “that will be in contact”.

8. In Section 9.6, Note 8, replace "has" with "is" or add "been found" after "has". Response: The word “has” was replaced with “been found”.

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9. In Section 9.8, suggest revising from "spread evenly between the loading platens" to "spread one half on the top loading platen and one half on the bottom loading platen". Response: The sentence was revised to “Divide the remaining adhesive in half and spread one half evenly on the top loading platen and the other half evenly on the bottom loading platen, ensuring that the grooves are filled.”

10. In Section 9.10, revise from "gluing jig" to "gluing apparatus" for consistency with terminology. Response: The suggested change was made.

11. In Section 9.14, the first two sentences should remain combined or if kept as separate sentences, revise beginning of 2nd sentence from "Taking" to "Take". Response: The suggested change was made.

12. In Section 11.1.3, 1st line, revise from "center- mounted" to "center-mounted" (i.e., delete space after the hyphen). Response: The suggested change was made.

13. In Section 11.1.9, revise from "0.8-mm wire" to "0.8-mm carbon steel wire for consistency with terminology in Section 6.7. Response: “0.8-mm wire” was changed to “carbon steel wire” for consistency with the revised Section 6.7.

14. In Section 11.1.10, revise from "Figure 7to" to "Figure 7 to". Response: The suggested change was made.

15. In Figure 6 caption, suggest revising from "for example an 80-mm diameter" to "for example 80-mm diameter". Response: The suggested change was made.

16. In Figure 7 caption, suggest revising from "for example a 130-mm diameter" to "for example 130-mm diameter". Response: The suggested change was made.

17. In Section 11.1.14, revise from "1/3rd" to simply "1/3" in three locations [2nd line (1X) & 3rd line (2X)], to make similar to the latter part of the same section. Response: The suggested change was made.

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18. In Section 11.2, should this be revised from "Dynamic Modulus Fingerprint Test" to "Fingerprint Dynamic Modulus Test" to coincide with revision to add Section 3.10? Response: Yes, the suggested change was made.

19. In Section 11.2.1, 1st line, similarly to comment 18) above, should "dynamic modulus fingerprint test" be revised to "fingerprint dynamic modulus test"? Response: Yes, the suggested change was made.

20. In Section 12.3.4, the 3rd and 5th "where" parameters and their definitions are not properly vertically aligned with each other. Response: The alignment was fixed.

21. In Section 13.2.4, add space between bottom of Table 6 and the Table 7 title. Response: The suggested change was made.

22. In Section 13.6.7, 1st line, revise from "adjustment , K" to "adjustment, K" (i.e., delete space after "adjustment" and before the comma). Response: The suggested change was made.

23. In Section 13.6.7, 2nd line, suggest deleting hyphen at end of 2nd sentence. Response: The suggested change was made.

24. In Section 14.2.2, at end, add "and". Response: The suggested change was made.

25. In Section 14.2.3, at end, revise from "(DR); and" to "(DR).". Response: The suggested change was made.

Comments from Changlin Pan of the Nevada Department of Transportation

1. 9.11, It would be nice to mention that the gauge studs are not in the same plane as the loading platen screws openings. It is somewhat discussed in section 9.2 but might be appropriate to include it here if the gauge point are glued first. Response: It is not relevant in Section 9.11 since that sections refers to gluing of the loading platens to the specimen and not the gauge points. The location of the screw openings is not critical when gluing the loading platens, only when affixing the gauge points.

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2. X3, Remove hyphens in Section X3.1 and X3.2 to be consistent. Response: The use of hyphens is appropriate when the number is used as a modifier that precedes a noun. Sections X3.1 and X3.2 were reviewed and revised accordingly.

Comments from Bret Steven Trautman of the Missouri Department of Transportation

1. It appears previous Sections 5.1 and 5.2 were combined to form one section. Section 5.1 was deleted while Section 5.2 was changed to Section 5.1. When the changes are accepted, not sure if the section number will be located at the beginning of the section. Response: Accepting changes was tried and Section 5.1 was displayed so the numbering is correct.

2. It appears previous Sections 11.1.7 and 11.1.8 were combined to form one section. Section 11.1.7 was deleted while Section 11.1.8 was changed to Section11.1.15. When the changes are accepted, not sure if the section number will be located at the beginning of the section. Response: Accepting changes was tried and the numbering appeared correctly.

3. It appears previous Section 12.32 and previous Note 10 were combined to form one section. Section 12.32 was deleted while Note 10 was changed to Section 13.6.10. When the changes are accepted, not sure if the section number will be located at the beginning of the section. Response: Accepting changes was tried and the numbering appeared correctly.

Comments from Brian K. Egan of the Tennessee Department of Transportation

1. Figure 3 and section 6.4 replace deformation sensors to LVDTs. Response: Deformation sensors is consistent with the terminology used throughout the standard. The standard does not preclude the use of alternative deformation sensors to LVDTs.

2. Section 6.2. Recommend to add "It is recommended to use the dummy specimen made with an identical mixture to a specimen to be tested. If not possible, recommend using identical NMAS to a specimen to be tested." Response: The suggested change was made.

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For ballot prep only. Do not remove this header. Do not upload this file to Current Production Materials Library.





American Association of State Highway and Transportation Officials 555 12th Street NW, Suite 1000 Washington, DC 20004

59 of 141







1. SCOPE

1.1. This test method covers procedures for preparing and testing both laboratory-compacted and field-cored asphalt mixture specimens to determine the damage characteristic curve and fatigue analysis parameters via the direct tension cyclic fatigue test using the asphalt mixture performance tester (AMPT).

1.2. This standard is intended for dense-graded mixtures with nominal maximum aggregate size less than or equal to 19.0 mm (0.75 in.). Mixtures with a nominal maximum aggregate size greater than 19.0 mm (0.75 in.) should be tested following TP 107.

1.3. This standard may involve hazardous material, operations, and equipment. This standard does not purport to address all safety problems associated with its use. It is the responsibility of the user of this procedure to establish appropriate safety and health practices and to determine the applicability of regulatory limitations prior to use.

2. REFERENCED STANDARDS


M 320, Standard Specification for Performance-Graded Asphalt Binder

M 332, Standard Specification for Performance-Graded Asphalt Binder Using Multiple Stress Creep Recovery (MSCR) Test

PP 99, Preparation of Small Cylindrical Performance Test Specimens Using the Superpave Gyratory Compactor (SGC) and Field Cores

TP 107, Determining the Damage Characteristic Curve of Asphalt Mixtures from Direct Tension Cyclic Fatigue Tests

TP 132, Determining the Dynamic Modulus for Asphalt Mixtures Using Small Specimens in the Asphalt Mixture Performance Tester (AMPT)

2.2. Federal Highway Administration:

up to

98

98

<#>R 30, Mixture Conditioning of Hot Mix Asphalt (HMA)¶<#>R 62, Developing Dynamic Modulus Master Curves for Asphalt Mixtures ¶<#>R 84, Developing Dynamic Modulus Master Curves for Asphalt Mixtures Using the Asphalt Mixture Performance Tester (AMPT)¶<#>T 378, Determining the Dynamic Modulus and Flow Number for Asphalt Mixtures Using the Asphalt Mixture Performance Tester (AMPT)¶

<#>ASTM Standard:¶<#>E4, Standard Practices for Force Verification of Testing Machines¶

60 of 141



Cyclic Fatigue Index Parameter (Sapp) for Asphalt Performance Engineered Mixture Design, FHWA-HIF-091, 2019.

Development of Asphalt Mixture Performance Related Specifications, Final Report, FHWA Project No. DTFH61-08-H-00005, 2020.

2.3. NCHRP Report:

Equipment Specification for the Simple Performance Test System, Version 3.0, Prepared for National Cooperative Highway Research Program (NCHRP), October 16, 2007.

2.4. Other Document:

Lee, K., S. Pape, C. Castorena, B.S. Underwood, and Y.R. Kim. “Strain-Level Determination Procedure for Small-Specimen Cyclic Fatigue Testing in the Asphalt Mixture Performance Tester,” Transportation Research Record: Journal of the Transportation Research Board, Vol. 2673, pp. 824-835, 2019.

Li, X. and N. H. Gibson. “Using Small Specimens for AMPT Dynamic Modulus and Fatigue Tests,” Asphalt Paving Technology, Journal of the Association of Asphalt Paving Technologists, Vol. 82, pp. 579–615, 2013.

3. TERMINOLOGY

3.1. alpha term ( )—value corresponding to the slope of the relaxation modulus master curve which is used in the accumulation of damage with time.

3.2. command load—the load level that a user inputs to the control software of the AMPT equipment.

3.3. cyclic fatigue index parameter (Sapp)—the apparent damage capacity of the material.

3.4. cyclic pseudo secant modulus (C*)—the secant modulus in stress–pseudo strain space for a single cycle. This pseudo modulus differs from C because it is computed using a steady-state assumption and is used only with cycle-based data.

3.5. damage (S)—the internal state variable that quantifies microstructural changes in asphalt mixtures.

3.6. damage characteristic curve (C versus S curve)—the curve formed when plotting the damage on the x-axis and the pseudo secant modulus on the y-axis. It defines the unique relationship between the structural integrity and amount of damage in a given mixture.

3.7. dynamic modulus (|E*|)—the peak-to-peak stress divided by the peak-to-peak axial strain resulting from sinusoidal loading measured during the steady-state period.

3.8. dynamic modulus ratio (DMR)—the ratio between the fingerprint dynamic modulus and the dynamic modulus value from a master curve construction, both evaluated at the same temperature and frequency condition. This value is also used to characterize specimen-to-specimen variability.

3.9. end failure—specimen failure in which the macrocrack develops outside the range of one or more axial deformation sensors. Several example end failure locations are shown in Figure 1.

2018

<#>National Cooperative Highway Research Report 629: Ruggedness Testing of the Dynamic Modulus and Flow Number Tests with the Simple Performance Tester, Appendix E, Final Version of the SPT Equipment Specifications. NCHRP, Transportation Research Board, 2008.¶

¶<#>complex modulus (E*)—complex number that defines the relationship between stress and strain for a linear viscoelastic material.¶

concrete

norm of the E*, which is calculated by dividing

measured during the steady-state period.

fingerprint

<#>failures:¶

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Figure 1—Example End Failure Locations

3.10. fingerprint dynamic modulus (|E*|fingerprint)—the dynamic modulus that is measured on the test specimen prior to performing the cyclic fatigue test.

3.11. middle failure—specimen failure in which the macrocrack develops within the range of all axial deformation sensors. Several example middle failure locations are shown in Figure 2.

Figure 2—Example Middle Failure Locations

3.12. number of cycles to failure (Nf)—the cycle in which the product of peak-to-peak stress and cycle number reaches a maximum value after a stable increase during cyclic loading.

3.13. phase angle ( )—the angle, expressed in degrees, between an applied sinusoidal stress and the resulting sinusoidal strain measured during the steady-state period.

3.14. pseudo energy-based fatigue failure criterion (DR)—the average loss of integrity of the material during the fatigue loading.

3.15. pseudo secant modulus (C)—the secant modulus in stress–pseudo strain space.

3.16. pseudo strain ( R)—a quantity that is similar to strain but does not include time effects. Pseudo strain is calculated by solving the convolution integral of the strain and E(t).

3.17. relaxation modulus (E(t))—the quotient of the stress response of a material with time to a constant step amplitude of strain.

3.18. resulting load—the load level that the AMPT applies as a result of the command load.

I have not been able to view this figure or figure 1 in the version provided by AASHTO.

cycle

measured phase angle

drops sharply

<#>fatigue analysis coefficients (k1, k2, k3)—fitting coefficients to describe the classical stress (or strain) versus cycles to failure relationship.¶

slope of the linear relationship between sum of (1 – C) up to failure and the number of cycles to failure. The physical meaning is the average loss of integrity of the material during the fatigue

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3.19. storage modulus (E')—the elastic component of the dynamic modulus.

3.20. test specimen—a 38-mm (1.50-in.) diameter by 110-mm (4.33-in.) tall cylindrical specimen cored and sawed from either an SGC specimen or field core.


4.1. An actuator displacement-controlled repeated cyclic loading is applied to an asphalt mixture test specimen until failure. The applied stress and on-specimen axial strain response are measured and used to calculate the necessary quantities. The analysis of this test procedure requires dynamic modulus data conducted in accordance with TP 132. The test outcomes are two material functions, the C versus S curve and the DR. It is important to recognize that this document pertains to direct tension testing in an AMPT. Test procedures will differ if using other machines and it is recommended that more specialized procedures be developed for these other machines.


5.1. The C versus S curve and the DR are independent of temperature, frequency, and mode of loading. The combination of linear viscoelastic properties, the C versus S curve, and the DR can be used to calculate Sapp. The procedure to calculate Sapp is provided in Appendix X2. The combination of the C versus S curve and the DR can also be used with pavement response models to predict the fatigue behavior of asphalt pavements.

6. APPARATUS

6.1. Asphalt Mixture Performance Tester—An AMPT or other machine meeting or exceeding the requirements of the equipment specification for the Simple Performance Test (SPT) System, Version 3.0, with the additional capability to conduct direct tension testing. An example schematic of an AMPT with direct tension capability is shown in Figure 3.

Test Specimen

Actuator with Cyclic Tension-Compression Capability

Load Cell

Loading Platen (Bottom)

Deformation Sensors

Inside AMPT

Loading Platen (Top)

AMPT Platen (Top)

AMPT Platen (Bottom)Spacer Platen (Bottom)

Spacer Platen (Top)

Figure 3—Example Schematic of an AMPT with Direct Tension Testing Capability

or T 378

relationship between the damage (S) and the pseudo secant modulus (C) is determined and expressed as the damage characteristic curve. It is important to recognize that this document

ry

loading

damage characteristic curve represents the fundamental relationship between damage and material integrity for asphalt mixturesare independent of temperature, frequency, and mode of

This property is independent of temperature, frequency, and mode of loading. Combined with the…

damage characteristic

analyze asphalt mixture fatigue characteristics.¶

in-service

mixtures

system

Equipment Specifications for the Simple Performance

, as

Loading Platen (Bottom)

Inside AMPT

Loading Platen (Top)

AMPT Platen (Top)

AMPT Platen (Bottom)

General

Setup

63 of 141



6.2. Dummy specimen (optional)—A 38-mm (1.50 in.) diameter by 110-mm (4.33 in.) tall cylindrical specimen cored and sawed from an SGC specimen with a thermocouple or other calibrated temperature-measuring device mounted in the center to check the temperature. It is recommended to use a dummy specimen made with an identical mixture to a specimen to be tested. If not possible, it is recommended that a mixture with identical NMAS as the one to be tested be used as the dummy specimen.

6.3. External Conditioning Chamber (optional)—An environmental chamber for conditioning the test specimens to the desired testing temperature. The chamber shall be capable of controlling the temperature of the test specimen over a temperature range of 9 to 21°C (48 to 70°F) to within ±0.5°C (±1°F). The chamber shall be large enough to accommodate at least a single test specimen and the “dummy” specimen.

6.4. Axial Deformation Measurement System—Axial deformations shall be measured in the middle 70 mm ± 1 mm (2.76 in. ± 0.04 in.) of the test specimen using sensors mounted between gauge points that are glued to the test specimen. The deformations shall be measured at three locations approximately 120 degrees apart.

70 ± 1 mm

AA

Figure 4—General Schematic of Gauge Points (Not to Scale)

6.5. Loading Platens—Are glued to the top and bottom of the test specimen to transfer the load from the testing machine to the test specimen. The diameter of the loading platens shall be 37.8 to 39.2 mm (1.49 to 1.54 in.). These platens should be made of hardened or plated steel or anodized high-strength aluminum. Materials that have linear elastic moduli and hardness lower than that of 6061-T6 aluminum shall not be used. The surface of each loading platen that will be in contact with the epoxy shall be grooved to provide better adhesion between the epoxy adhesive and platen. The top loading platen shall be designed so that it can be mated to the test machine without inducing any loading eccentricity.

Note 1—It is recommended the grooves in the loading platens be approximately 0.6 mm (0.02 in.) deep and spaced laterally by a distance of approximately 1.9 mm (0.07 in.). The grooving pattern can be concentric circle, spiral, or cross-hatched. A V-shaped or U-shaped groove is suggested. The 60-degree point threading bit has been used successfully for making the grooves.

6.6. Shims—Metal strips approximately 6.25 mm (0.25 in.) to 12.5 mm (0.5 in.) wide having a minimum length of 50 mm (2.0 in.) and ranging in thickness from at least 0.05 mm (0.002 in.) up to 0.762 mm (0.03 in.) in maximum increments of 0.05 mm (0.002 in.) shall be used to fill gaps

5

25

41

77

a

with a thermocouple or other calibrated temperature-measuring device mounted at the center for temperature verification.

(2.76 in.)

or four locations 90 degrees apart

70 ± 1 mm

adhered

38 ± 1

50

± 0.04

u

s propertie

s

properties

64 of 141



between the top of the test specimen loading platen and AMPT platen or spacer platen if one is used

Note 2—Tapered leaf feeler gauges have been used successfully (Grainger Catalog Number 42DJ75 or equivalent).

6.7. Diameter Carbon Steel Wire—0.8-mm (0.031-in.) diameter carbon steel wire.

Note 3—McMaster Carr Catalog Number 9666K56 has been used successfully.

6.8. Loading Platen Gluing Apparatus (optional)—Used for gluing the loading platens to the test specimen with epoxy adhesive. The device should ensure that the loading platens and test specimen are all centered, that the two loading platens are held parallel, and that the test specimen is standing perpendicular to the loading platens. The weight resting on the test specimen during curing of the adhesive shall not exceed 0.03 kN (6.7 lb).

May be called end plates or end platens colloquially.¶Ball Bearing (optional)—Users may place a ball bearing in the dent of the upper loading platen or spacer platen in an attempt to account for loading eccentricity. Extra care should be taken using the ball bearing because if the screws are not tightened evenly around then excessive tensile stresses will develop on one side of the test specimen due to an induced loading eccentricity.¶

02

4.5

65 of 141



Figure 5—Example of a Loading Platen Gluing Apparatus

6.9. Spacer Platens (optional)—May be required to attach the loading platens to the AMPT platens due to the small test specimen size.

6.10. Epoxy Adhesive—Is required to affix the loading platens and gauge points to the test specimen. The epoxy adhesive must be capable of maintaining adhesion between metal and asphalt mixture under cyclic tension loading. The epoxy should have a working time greater than or equal to the time needed to glue loading platens and gauge points to the test specimen (typically five minutes).

test specimen

concrete

66 of 141



Note 4—Devcon 10240 Plastic Steel 5 Minute Putty has been used successfully (McMaster Carr Catalog Number 74575A63).

6.11. Gauge Point Gluing Apparatus (optional)— A device used to position and place the gauge points on the test specimen and hold them there until the epoxy adhesive cures. The device shall be capable of holding the gauge points at a separation distance of 70 mm ± 1 mm, approximately in the middle of specimen, measured center to center of the gauge points. It should also be capable of attaching the gauge points approximately 120 degrees apart.

7. HAZARDS

7.1. Use standard laboratory safety precautions, equipment, and personal protection equipment when preparing and testing asphalt mixture specimens.

8. TESTING EQUIPMENT CALIBRATION

8.1. The guidelines provided in TP 132 shall be followed to ensure that the test equipment and on-specimen measurement devices are properly calibrated.

8.2. If any of the verifications yield data that does not comply with the accuracy specified, the problem shall be corrected prior to further testing.

8.3. The hydraulic machine shall be properly tuned in displacement control mode to enable the use of the strain selection guidance in this standard. Consult the equipment manufacturer for guidance on the specific equipment.

9. TEST SPECIMEN MOUNTING AND INSTRUMENTATION PROCEDURE

9.1. Prepare at least three test specimens at the target air void content ±0.5 percent in accordance with PP 99.

9.2. Attach the gauge points to each test specimen with the epoxy adhesive in accordance with the manufacturer’s instructions. Avoid placing gauge points directly in line with screw holes in the loading platens, which will be used to attach the test specimen to the testing machine.

Note 5—Users may attach gauge points before or after the loading platens. However, the gauge point gluing apparatuses may require that the loading platens and gauge points be attached in a specific order.

9.3. Verify that the gauge length is 70 mm ± 1 mm (2.76 in. ± 0.04 in.), measured center to center of the gauge points.

9.4. Thoroughly clean all loading platens including both new and used loading platens.

9.4.1. Heavily brush the surface of each loading platen that will be in contact with the epoxy using either a hand-operated wire brush, sandpaper, or a wire brush attached to a standard electric drill.

9.4.2. Wipe the surface clean of dust and residue by using a towel dipped in acetone or similar solvent.

9.5. Wipe both ends of the test specimen clean of any residual dust.

9.6. Weigh out an appropriate amount of each part of the epoxy adhesive to glue the loading platens and test specimen to one another.

41

¶

378

In displacement control mode, the tuning shall be such that there is a sinusoidal actuator deformation shape and the actuator displacement returns close to the initial position on the first cycle, as this will ensure the cycles are uniform and the input strain closely matches the output strain. Consult the equipment manufacturer for

Test specimens 38-mm (1.50-in.) diameter by 110-mm (4.33-in.) height shall be fabricated in …

the

Take care to a

Note 2—The same epoxy adhesive used for the loading platens has been found to be satisfactory for attaching the gauge points.¶

53

by first h

ing

face of each loading platen

After cleaning the loading platen, w

any

Using the same towel but with only a small amount of solvent, wipe both ends of the test specimen clean of any residual dust.

adhere

The gluing process will require approximately 5 min, so prepare an epoxy adhesive that is appropriate for this length of working time.¶

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Note 6—Approximately 6 g (0.21 oz.) of the epoxy adhesive has been found suitable for adhering 38-mm (1.50-in.) diameter test specimens.

9.7. Fill in any surface voids and pores in the top and bottom surfaces of the test specimen with the adhesive.

9.8. Divide the remaining adhesive in half and spread one half evenly on the top loading platen and the other half evenly on the bottom loading platen, ensuring that the grooves are filled.

9.9. If gluing test specimens with the gluing apparatus, continue to Section 9.10. If gluing test specimens with the AMPT, skip to Section 9.16.

9.10. Insert and secure the loading platens into the gluing apparatus and gently place the test specimen on top of the bottom loading platen, as close as possible to the center.

9.11. Engage the centering mechanism to center the test specimen on the loading platen.

9.12. Lower the top platen into position and secure if necessary. The final adhesive thickness should be approximately 1 mm (0.04 in.).

9.13. Allow the epoxy adhesive to reach its initial set before moving the test specimen from the gluing apparatus.

9.14. Remove the test specimen from the gluing apparatus after initial set. Take special care to support the entire test specimen from the bottom loading platen. Do not lift the test specimen by the top loading platen to ensure tension is not applied to the test specimen and epoxy adhesive.

9.15. Skip to Section 9.19.

9.16. Insert and secure the loading platens to the AMPT and gently place the test specimen on top of the bottom loading platen, as close as possible to the center.

9.17. Set the command load to 0.03 kN (6.7 lb) compressive force.

9.18. If removing the test specimen from the AMPT before testing, then allow the epoxy adhesive to reach its initial set before moving. Take special care to support the entire test specimen from the bottom loading platen. Do not lift the test specimen by the top loading platen, to ensure tension is not applied to the test specimen and epoxy adhesive.

9.19. Allow the epoxy adhesive to reach a functional cure before testing. Follow the manufacturer’s recommendation to determine the time needed to reach functional cure.

10. TEST INFORMATION

10.1. This procedure is designed to first test a specimen, at a low strain to obtain a linear viscoelastic fingerprint and then test the specimen at a higher strain until it fails. Both tests are performed at a frequency of 10 Hz in oscillation (cyclic) mode and at a constant temperature prescribed in Section 10.3.

10.2. A total of three acceptable tests are required, with test specimens experiencing middle failure between 2,000 and 80,000 cycles to failure, and with a DMR between 0.85 and 1.15.

10.3. The testing temperature shall be selected using Table 1 or Table 2, where the specified PG of the binder material is used to determine the test temperature. Table 1 is used for PG grades developed

64

Devcon 10240 Plastic Steel 5 Minute Putty

been found to be

between the

s

jig

jig

jig

, t

ing

ll

test

the test

s

specific temperature and frequency

to obtain linear viscoelastic fingerprints, and then at the desired frequency and temperature until failure.

9

can

68 of 141



using M 320, or PG grades designated as “S” in M 332. Table 2 is used for PG grades designated as “H”, “V” or “E” in M 332. If the mixture contains recycled material and the PG of the virgin binder was adjusted to account for this recycled material, then select the temperature based on the PG of the virgin binder that would have been used for a mixture without any recycled materials.

Table 1—Recommended Test Temperatures for Different Standard PG Binder Grades

PG Low Temperature,

°C

Test Temperature, °C

PG High Temperature, °C

46 52 58 64 67 70 76 82 –10 15 18 21 21 21 21 21 21

–16 12 15 18 21 21 21 21 21 –22 9 12 15 18 18 21 21 21

–28 9 9 12 15 15 18 21 21

–34 9 9 9 12 12 15 18 21

–40 9 9 9 9 9 12 15 18

–46 9 9 9 9 9 9 12 15

AASHTO

AASHTO

AASHTO

a binder with a lower (softer) PG was used in lieu of the originally specified PG, defer to the originally specified PG when selecting the testing temperature.¶Note 5—The temperature used to conduct this test is selected to produce a satisfactory testing condition. The models used to analyze this test can translate satisfactory results at one temperature to a wide range of temperature conditions.¶Note 6—For binders graded with a PG high temperature of 67, round down to 64 to use Table 1.¶

Note 5—The temperature used to conduct this test is produce a satisfactory testing condition. The models used to analyze this test can translate satisfactory results at one temperature to a wide range of temperature conditions.¶Note 6—For binders graded with a PG high temperature of 67, round down to 64 to use Table 1.¶

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Table 2—Recommended Test Temperatures for Different PG Binder Grades with MSCR “H”, “V”, or “E” Designations

PG Low Temperature,

°C

Test Temperature, °C

PG High Temperature, °C

46 52 58 64 67 70 76 82 –10 18 21 21 21 21 21 21 21 –16 15 18 21 21 21 21 21 21

–22 12 15 18 21 21 21 21 21

–28 9 12 15 18 18 21 21 21

–34 9 9 12 15 15 18 21 21

–40 9 9 9 12 12 15 18 21

–46 9 9 9 9 9 12 15 18

11. PROCEDURE

11.1. Test Setup:

11.1.1. Spacer platens may need to be placed between the loading platens and AMPT platens to compensate for the reduced height and diameter of the test specimens. If so, attach the spacer platens to the machine according to the manufacturer’s instructions.

11.1.2. If using an external conditioning chamber to temperature-condition the test specimens, continue to Section 11.1.3. If using the AMPT testing chamber to temperature-condition the test specimens, skip to Section 11.1.5.

11.1.3. Insert the test specimens to be tested and the “dummy” specimen with the center-mounted temperature monitoring device into the external conditioning chamber and start the temperature control of the AMPT.

11.1.4. Allow the test specimens to reach the specified testing temperature ±0.5°C (±1°F) by monitoring the temperature of the “dummy” specimen.

11.1.5. Open the AMPT testing chamber and note the time.

11.1.6. Insert the test specimen into the testing machine and tighten the lower loading platen securely to the AMPT platen or spacer platen.

11.1.7. Bring the actuator into position and apply 0.01 kN (2 lb) to 0.02 kN (4 lb) of seating load.

11.1.8. Loosely attach the top loading platen to the AMPT.

Note 7—Some equipment manufacturers use spacer platens to allow mounting the small specimen geometry. In this case, follow the manufacturer’s instructions for attaching the platens to the AMPT.

11.1.9. Check the maximum gap between the loading platen and the AMPT platen or spacer platen using the carbon steel wire. If the maximum gap is greater than 0.8 mm (0.03 in.), discard the test specimen. If the maximum gap is less than 0.8 mm (0.03 in.), continue to the next section.

11.1.10. Insert the thickest shim possible into the location of the maximum gap without using excessive force. Insert the shim as shown in Figure 6 or Figure 7 to fill the gap.

¶

approximately

.2

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Spacer Platen

Loading Platen

The Thickest Shim

Thinner Shims

Mounting Bolt

The First Bolt to be Tightened

Spacer Platen

Loading Platen

Test Specimen

Shims

A A

Figure 6—Diagram of acceptable shim placement for example 80-mm diameter spacer platen.

Loading Platen

Thinner Shims

The Thickest Shim

The First Bolt to be Tightened

Spacer Platen/AMPT Platen

Loading Platen

Test Specimen

Shims

A A

Figure 7—Diagram of acceptable shim placement for example 130-mm diameter spacer platen.

11.1.11. If the maximum gap is greater than 0.05 mm (0.002 in.), continue to Section 11.1.12. Otherwise, skip to Section 11.1.13.

11.1.12. Insert an additional thinner shim on each side of the thickest shim from Section 11.1.10 as shown in Figure 6. Again, use the thickest shims possible to fill the gap without excessively forcing the shims into place.

Note 8—The two thinner shims do not need to be the same thickness.

11.1.13. Hand tighten all bolts by starting with the bolt at the opposite side of the maximum gap.

11.1.14. Tighten all bolts evenly by starting with the bolt at the opposite side of the maximum gap and turning the bolt approximately 1/3 of a complete turn (120 degrees). Go to the next bolt and use the same 1/3 turn. Continue the sequence of 1/3 turns on each next bolt until all bolts have received a single 1/3 turn. Repeat this pattern of 1/3 turns on each bolt until all bolts are securely hand tightened. Avoid overtightening the bolts.

11.1.15. Set the command load to 0 kN. The resulting load shall be ± 0.01 kN (± 2 lb) of the command load.

Quickly secure the top loading platen to the top AMPT platen or spacer platen, tightening screws evenly around and making sure not to overtighten any screws, which can shear the specimen.¶Note 7—Shims may be placed between the top loading platen and the AMPT platen to account for any small gaps. This is done at the user’s discretion. Users should use the ball bearing for test specimens which exhibit (after the seating load is applied) any gap between the loading platens and AMPT platen in excess of 1 mm (0.04 in.).¶Reduce the load on the specimen to 0 kN

0 lb

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11.1.16. Attach the sensors to the test specimen gauge points. Position each sensor in a location along its travel range where the elongation of the test specimen will not exceed the range of the sensors as it undergoes damage and the compression during the fingerprint can be measured. This may not be the zero position; the exact position depends on the sensors.

11.1.17. Close the testing chamber and allow the testing chamber temperature to return to the test temperature.

11.1.18. Note the time that the testing chamber returns to the test temperature.

11.1.19. Calculate the duration of time from when the chamber was opened to when it returns to the test temperature by using the times recorded in Section 11.1.5 and 11.1.18. This duration is referred to as the test setup time (min).

11.1.20. Determine the ambient temperature and calculate the difference between the ambient temperature and test temperature. This difference is denoted as T.

11.1.21. Condition the test specimen in the closed chamber by allowing it to rest for the duration indicated in Table 3. This allows the test specimen’s internal temperature to return to the test temperature ± 0.5°C (± 1°F). If the test specimen is not conditioned in an external conditioning chamber prior to setup, use the “AMPT Conditioned” column to determine the duration

Table 3—AMPT Conditioning Time for Different Test Setup Times

| T| (°C)

AMPT Conditioning Time (minutes)

AMPT Conditioned

Test Setup Time (min) from Section 11.1.19

< 5 5-10 10-20 > 20

15 60 NA 40 50 60 14 60 NA 40 50 60 13 60 NA 40 50 60 12 50 NA 40 40 50 11 50 NA 40 40 50 10 50 NA 40 40 50 9 50 30 40 40 50 8 50 30 30 40 50 7 50 30 30 40 50 6 40 20 30 30 40 5 40 20 30 30 40 4 40 20 20 30 40 3 30 10 20 20 30 2 30 0 10 20 30 1 20 0 0 0 20

*NA = not applicable because the test machine cannot return to the test temperature in this amount of time for the given difference in temperature.

11.1.22.

11.1.22. Adjust, balance, and zero the electronic measuring system if the AMPT does not automatically adjust, balance, and zero.

11.2. Fingerprint Dynamic Modulus Test:

11.2.1. Input the required information for the fingerprint dynamic modulus test into the equipment control software. The fingerprint test shall be performed at a frequency of 10 Hz, at a target strain range of

, but

on

also

ing

, and c

period

and

Allow

to reach the specified testing temperature ± 0.5°C (± 1°F). For most testing machines, use Table 3

to determine the minimum length of time the test specimen must condition in the AMPT chamber following setup. If

<#>If the test specimen is not conditioned in an external chamber prior to setup, use the “AMPT Condition” column.¶

¶| T| (°C)

Dynamic Modulus

fingerprint

72 of 141



50 to 75 microstrain, at the target test temperature, and in the tension-compression mode of loading.

Note 9—Some software may require input of an estimated dynamic modulus value to estimate the starting load amplitude. In this case, enter a value similar to the modulus obtained during frequency sweep testing (using TP 132) if available. If not available, enter a conservative (low) estimate of the dynamic modulus so that the initial load does not damage the test specimen.

11.2.2. Start the fingerprint test. The AMPT shall calculate the load level necessary to achieve 50 to 75 microstrain using the results of these first few cycles and then apply this load level for 50 cycles. A minimum of 50 data points per cycle shall be recorded using the equipment control software.

11.2.3. Review the average peak-to-peak strain determined by the control software for the last five cycles. If the peak-to-peak strain exceeds 150 microstrain or the data quality indicators given in Table 4 are not met, discard the test specimen.

11.2.4. The test specimen shall rest at a load of 0 kN ± 0.01 kN (0 lb ± 2 lb) for a minimum of 5 min following the fingerprint testing.

11.3. Cyclic Fatigue Test:

11.3.1. Perform a constant positive movement actuator oscillation (cyclic) fatigue experiment at a frequency of 10 Hz (e.g., a pull-pull actuator displacement test). Use a strain level that will result in a test length between 2,000 and 80,000 cycles to failure. Guidance on selecting an appropriate strain level is given in Appendix X1.

11.3.2. Allow the test to run until the number of cycles to failure is achieved, the machine limits are reached and the test stops automatically, or the test reaches 80,000 cycles. If end failure occurs, the data must be discarded from analysis and the test must be repeated on a new test specimen. Exclude any tests with a number of cycles to failure greater than 80,000 or less than 2,000 from analysis.

11.4. Repeat the steps in Sections 11.1 through 11.3 on the remaining test specimens.

12. TEST DATA

12.1. All of the test data described in this section shall be automatically generated using the AMPT control software.

12.2. Fingerprint data:

12.2.1. Calculate load standard error, strain standard error, strain uniformity, and phase angle uniformity using the last 5 cycles of the fingerprint cycles using the algorithms described in equipment specification for the Simple Performance Test (SPT) System, Version 3.0.

12.2.2. Accept fingerprint data only if it meets the data quality statistics given in Table 4. Repeat tests as necessary to obtain quality data.

Table 4—Data Quality Statistics Requirements for Fingerprint Test

Indicator Limit

Standard error of the applied stress 10%

Average standard error of the measured strains 10%

98

or T 378

Compute the dynamic modulus for the last five cycles according to the method recommended in TP 132 or T 378. …

20

a clear peak in the phase angle is observed

The peak in phase angle is shown in Figure 5.

¶

0

1000

2000

3000

4000

5000

6000

7000

8000

0 2000 4000

Mod

ulus

(MP

a)

Dynamic Modulus

Phase Angle

Figure 6—Dynamic Modulus and Phase Angle Changes throughout Testing¶

73 of 141



Uniformity coefficient of the measured strains 35%

Uniformity coefficient for the phase angle measurements 3°

12.3. Cyclic fatigue data:

12.3.1. Prepare a summary of the first five loading cycles from the cyclic fatigue test. This summary should contain at a minimum, the following data in increments of 0.001 s;

• Elapsed time since the beginning of loading. • Stress value for each time recorded, calculated by dividing the test specimen cross-

sectional area, calculated from the measured diameter, by the applied force during the test. • Strain value from each deformation sensor for each time recorded, calculated by dividing

the test specimen deformation measured from the sensor by the gauge length of the sensor gauge points.

• Average strain value for each time recorded, calculated by averaging the measured strains from individual sensors.

• Actuator displacement value for each time recorded.

12.3.2. Prepare a summary of the portion of the data from Section 12.3.1 that includes only the data from the beginning of loading until the first peak stress. Refer to this summarized data as Dataset 1.

12.3.3. Prepare a summary of the portion of the data from Section 12.3.1 that includes only the data from the beginning of cycle two through the end of cycle five. Refer to this summarized data as Dataset 2.

12.3.4. Calculate the actuator strain standard error for each cycle in Dataset 2. The standard error of the actuator strain is defined in Equation (1).

2

1

ˆ( )100%

ˆ4

n

i ii

o

x xSE

n x=

−

=−

(1)

where: SE = standard error of the actuator strain; xi = measured actuator strain at point i;

ˆix

= predicted actuator strain at point i from the sinusoid; n = total number of data points collected during the test; and

ˆox

= amplitude of the sinusoid.

12.3.5. Average the standard error values calculated in Section 12.3.4.

12.3.6. Accept cyclic fatigue data only if the average standard error is less than or equal to ten percent. Discard test results that fail to meet these requirements and consult the equipment manufacturer for guidance on tuning.

12.3.7. Prepare a summary of the remaining cyclic fatigue data. Refer to this summarized data as Dataset 3. The summary should contain at a minimum;

• Cycle number • Dynamic modulus for the cycle (calculated via the method in the equipment specification

for the Simple Performance Test (SPT) System, Version 3.0) • Peak-to-peak stress value for the cycle • Maximum stress value for the cycle

(1)

74 of 141



• Minimum stress value for the cycle • Peak-to-peak actuator strain value for the cycle • Peak-to-peak average strain value for the cycle • Peak-to-peak strain value for each deformation sensor for the cycle

13. CALCULATIONS

13.1. This section presents the equations used to calculate the pseudo strain, pseudo secant modulus, and damage parameter for the fatigue tests. All of the calculations in this section can be automatically performed using a combination of the AMPT control software and the FlexMAT™ spreadsheet v2.0 or later.

13.2. This section describes the steps necessary to analyze the dynamic modulus test results obtained from TP 132.

13.2.1. Compute the storage modulus, E , for each temperature and frequency combination measured via Equation (2).

* cos180

E E×

′ = × (2)

where:

E = storage modulus (kPa);

|E*| = dynamic modulus determined via experiment (kPa); and

= phase angle determined via experiment (degrees).

13.2.2. Determine the fitting coefficients in Equations (3) and (5) simultaneously using numerical optimization. The optimization shall minimize the objective function given in Equation (6). The optimization can be performed using the Solver function in Microsoft Excel®. The recommended initial estimates for coefficients when using units of kPa for storage modulus and °C for temperature are given in Table 5.

( )( ) ( )( )( )log

log(max E')log , log

1 RSigmoidal Sigmoidal R d g

bE T E b

e + × ω

−′ ′ω = ω = +

+ (3)

where:

E Sigmoidal( ,T) = storage modulus at a particular temperature and angular frequency (kPa);

E Sigmoidal( R) = storage modulus at a particular reduced angular frequency (kPa);

R = reduced angular frequency, Equation (4) (rad/s); and

b, d, g, max E = fitting coefficients.

R Taω = ω × (4)

where:

aT = time–temperature shift factor at a given temperature.

( ) ( )2 21 2 1 1 22

10 ref ref refa T a a T T a T a TTa

× + − × × × + × − ×

= (5)

where:

T = temperature (°C);

Tref = reference temperature (°C); and

a1, a2= fitting coefficients.

ALPHA-Fatigue software or the

described in the final report for the FHWA Project DTFH61-08-H-00005.

<#>Determine the E(t) Prony coefficients from the dynamic modulus and phase angle measured using T 378 or TP 132 and R 84. It is assumed that the relaxation modulus can be represented by Equation 1.¶

<#> ( )1

m

tN

mi

E t E E e−

∞

=

= + (1)¶

<#>where:¶<#>E(t) = relaxation modulus as a function of time, t, (kPa or psi);¶<#>E = long-time equilibrium modulus, (kPa or psi); ¶<#>Em = modulus of Prony term number m, (kPa or psi); ¶<#> m = relaxation time of Prony term m (s); and¶<#>N = number of Prony terms used.¶

Equation 2

(2)

or psi

or psi

75 of 141



( ) ( )( )2

1

log ' ( ) log '( )n

Sigmoidal R i R ii

Error E E=

= ω − ω (6)

where:

n = number of temperature and frequency combinations measured using TP 132.

Table 5—Recommended Initial Values for Fitting Coefficients in Equations (3) and (5).

max E (kPa) b d g a1 a2

2.5 107 4 -1.5 -0.5 0.005 -0.15

13.2.3. Compute the storage modulus via Equation (3) using the optimized fitting coefficients at 21 frequencies, each a decade apart, beginning with 62.83 10-15 rad/s and ending at 62.83 105 rad/s.

Determine the fitting coefficients in Equations (7) and (10) simultaneously using numerical optimization. The optimization shall minimize the objective function given in Equation (10). The optimization can be performed using the Solver function in Microsoft Excel® with the multistart option enabled. The recommended initial estimates for the coefficients are given in Table 6 when using units of kPa for storage modulus and °C for temperature. Use the constraints given in

13.2.4. Table 7; these apply when using units of kPa for storage modulus and °C for temperature.

12 2 1 00 2 2

1 2

0 00 0 00

'

' 'S P D

EE E

E E

E E E E

′ = +

+− −

(7)

where:

E00 = minimum storage modulus value (kPa);

E 1 = Equation (8) (kPa); and

E 2 = Equation (9) (kPa).

( ) ( ) ( )1 0 00' 1 cos cos2 2

hR E R E

hE E E

− κ −κπ π= − × + δ × ω × τ × + ω × τ × (8)

( )( ) ( )

( )

2 0 001

1 sin sin2 2'

hR E R E

R E

h

E E E

− κ −

−

κπ π+ δ × ω × τ × + ω × τ × +

= − ×

ω × τ × β

(9)

( ) ( )( )21 2

, 2 2 1 ,1

log ' log 'Sigmoidal i S P D ii

Error E E=

= − (10)

where:

E0 = maximum storage modulus value (kPa);

, , , h, β, τE = fitting coefficients;

E Sigmoidal = storage modulus (kPa), calculated via Equation (3) at each of the reduced frequencies defined in Section 13.2.3; and

E 2S2P1D = storage modulus (kPa), calculated via Equation (7) at each of the reduced frequencies defined in Section 13.2.3.

Table 7

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Table 6—Recommended Initial Values for Fitting Coefficients in Equations (7), (8), and (9).

h E00

(MPa) E0

(MPa) log( E)

2.5 0.1 0.5 1.0E+12 10 4.0E+4 -3

Table 7—Constraints for Fitting Coefficients in 2S2P1D Model.

Coefficient Constraint(s)

0, 20

0, 1

h

= 1012

E0 = 4 × 104

log ( E) –10, 10

13.2.5. Determine the Prony coefficients in Equation (11) using Equation (12).

2 2

2 21

101

Nm R m

R mm

EE β

=

ω ρ′ = +

ω ρ + (11)

[ ] { }1

m normmiE B E

−′= × (12)

where: [B]mi = the relaxation kernel matrix for determining the Prony coefficients; and {E }norm = the shifted storage modulus array for determining the Prony coefficients. where:

2 2

2 2 1i m

mii m

Bω ρ

ω ρ=

+ (13)

2 2 1 10norm S P DE E β′ ′= − (14)

Using the Prony coefficients, the relaxation modulus can be calculated using Equation (15).

( )1

m

n t

mi

E t E E e−

ρ

∞

=

= + (15)

where:

E(t) = relaxation modulus as a function of time, t, (kPa);

Em = modulus of Prony term number m, (kPa);

m = relaxation time of Prony term m (s); and

n = number of Prony terms used.

13.3. Compute the specimen-to-specimen normalization parameter using Equation 10 and denote this parameter as the DMR (Dynamic Modulus Ratio).

fingerprint*

*LVE

EDMR

E= (16)

Optimize the coefficients in Equations 3 and 7 simultaneously. Because measured data contain some variability, a smoothing process is needed to obtain reliable coefficients.¶

( ) ( )( )

( )log

log maxlog , log

1 RR

EE T E

e +

′ −′ ′= = +

+

(3)¶where:¶E ( ,T) = storage modulus at a particular temperature and angular frequency (kPa or psi);¶E ( R) = storage modulus at a particular reduced angular frequency (kPa or psi);¶

R = reduced angular frequency, Equation 6 (rad/s); ¶max = defined by Equation 4; and¶

, , = fitting coefficients.¶¶

max 1100 10,000

110

c

VMA VFA VMAE P A B

VM

A

×′ = − + +

−

(4)¶where:¶Pc = defined in Equation 5 (kPa or psi); ¶VMA = voids in mineral aggregate, percent; ¶VFA = voids filled with asphalt, percent;¶A = 4,200,000 for prediction in psi or 29,000,000 for prediction in kPa; and¶B = 435,000 for prediction in psi or 3,000,000 for prediction in kPa.¶¶

(10)

77 of 141



where: |E*|fingerprint = dynamic modulus determined from Section 11.2 (kPa); |E*|LVE = average representative dynamic modulus for the mixture of interest at the

temperature and frequency of interest (kPa), and computed by Equation (17); and

DMR = dynamic modulus ratio, which is the specimen variability compensation parameter.

2 22 2

2 2 2 21 1

*1 1

N Nm R m m R m

LVEm mR m R m

E EE E

∞

= =

= + ++ +

(17)

where: = angular frequency used in the fingerprint experiment;

aT = time–temperature shift factor for the fingerprint test temperature; R = reduced angular frequency, Equation 12, used in the fingerprint experiment; and

E , Em, m = Prony coefficient terms.

13.4. This section describes the steps necessary to calculate the continuum damage model power term, .

13.4.1. Determine the log-log slope of the storage modulus, E ( R) numerically using the 2S2P1D model representation of E ( R) in Equation (7) and denote as m.

13.4.2. Calculate value using Equation (18).

11

mα = + (18)

13.5. This section describes the steps necessary to calculate the pseudo secant modulus and damage for Dataset 1.

13.5.1. Compute the reduced time for each data point in Dataset 1 using Equation (19).

R

T

tt

a= (19)

where:

aT = time–temperature shift factor at a given temperature;

t = time measured from the experiment (s), and

tR = reduced time (s).

13.5.2. Compute the pseudo strain for each data point in Dataset 1 using the state variable formulation shown in Equation (20).

( )1 1 1

1

1 NR n n n

o mmRE

+ + +

=

= + (20)

where: ( )1R n+ = pseudo strain at the next time step;

ER = reference modulus, a value of 1 should be chosen; = elastic component of the pseudo strain (Equation (21)); m = pseudo strain contribution of Prony element m (Equation (22));

n = time step used in the calculation; = strain calculated for the current or subsequent time step;

or psi

or psi

Equation 11

(11)

<#> R Ta= ∗ (12)¶

<#>Separate the data into two parts. The first part, Dataset 1, comprises the data for the first half of the first loading path (from zero to first peak stress). The second part, Dataset 2, comprises the rest of the data.¶

<#>For Dataset 1, average all sensor readings and compute the average strain for all data points.¶<#>Calculate the axial stress for each data point in Dataset 1.¶

Equation 13

(13)

Equation 13

(14)

(Equation 15

Equation 16

78 of 141



tR = duration of the reduced time step, tRn+1 – tR

n; and tR = reduced time.

( )1 10n nE+ +

∞= (21)

( )1

1 1 101

R R

m m

t tn nn n n nm m m m

R

e E e Et

− −+

+ + +

∞

−= + × − = (22)

13.5.3. Compute the normalized pseudo secant modulus for each data point in Dataset 1 using Equation (23).

RC

DMR=

∗ (23)

where:

= stress (kPa);

13.5.4. Compute the change in damage, S, for each time step using Equation (24). Due to inherent electronic interference (data noise) during data acquisition, a few sequential data points may have positive C values. A few of these spurious data points do not negatively affect the overall value of damage (S), but they do complicate the calculation. An efficient method that accounts for these spurious data points is the piecewise function shown in Equation 19.

( ) ( ) ( )112

11 1

1

2

0

Ri i R i i

i

i i

DMRC C t C CS

C C

+

+− −

−

− − ≤=

>

(24)

where:

Ci = pseudo secant modulus at the current time step;

Ci–1 = pseudo secant modulus at the previous time step;

13.5.5. Determine the damage at each time step using Equation (25).

1

N

i ii

S S=

= (25)

where:

Si = cumulative damage at the current time step; and

Si = incremental damage for all time steps to be summed from the initial time step, i = 1, to the current time step, N.

13.5.6. Define the damage at the final point in Dataset 1 as SDataset 1.

13.6. This section describes the steps necessary to calculate the cyclic pseudo secant modulus and damage for Dataset 3.

13.6.1. Compute the peak-to-peak pseudo strain for each cycle in Dataset 3 using Equation (26). Rpp pp LVE

E= ∗ ∗ (26)

pp = average peak-to-peak axial strain; and Rpp = peak-to-peak pseudo strain.

13.6.2. Compute the cyclic pseudo secant modulus for each cycle in Dataset 3 using Equation (27).

(15)

(16)

Equation 17

(17)

<#>The continuum damage model power term, , is related to the log-log slope of the relaxation modulus, E(t). Its value is found numerically using the Prony series representation of the E(t) in Equation 1. Determine m, the maximum value of the tangential slope of the relaxation modulus versus time relationship in log-log scale, and determine the value using Equation 18.¶

<#>1

1m

= + (18)¶

Equation 19

(19)

<#> tR = change in the reduced time step; and¶<#> = continuum damage power term related to material time dependence, Equation 18.¶

Equation 20

(20)

<#>Compute the peak-to-peak strain for each sensor and each cycle in Dataset 2.¶<#>For each cycle in Dataset 2, average all sensor strains and denote this strain as the test peak-to-peak strain amplitude, pp.¶<#>Compute the peak-to-peak stress for each cycle in Dataset 2.¶<#>Compute the phase angle for each sensor and average the values together for each cycle. Depending on the test equipment (e.g., an AMPT), phase angle may be automatically calculated per sensor and averaged.¶

2

Equation 21

(21)

2

Equation 22

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pp

Rpp

CDMR

∗ =∗

(27)

where:

pp = peak-to-peak stress (kPa);

13.6.3. Compute the functional form factor, , for each cycle in Dataset 3 using Equation (28).

peak valley

peak valley

σ + σχ =

σ + σ (28)

where:

σpeak = peak tensile stress (kPa); and

σvalley = valley stress (kPa).

Note 10—For this calculation the sign convention should be such that the tension direction is positive.

13.6.4. Compute the tension amplitude pseudo strain for each cycle in Dataset 3 using Equation (29).

1

2R Rta pp

χ +ε = ε (29)

where: Rta = tension amplitude pseudo strain.

13.6.5. Compute the time within a cycle when tensile loading begins, tb, for each cycle in in Dataset 3 by using Equation (30).

( )1cos

62.83bt−

χ= (30)

13.6.6. Compute the time within a cycle when tensile loading ends, te, for each cycle Dataset 3 by using Equation (31).

( )12 cos

62.83et−

π − χ= (31)

13.6.7. Compute the form adjustment, K1, for each cycle in Dataset 3. This process uses a third order polynomial to approximate the value of K1 for a given . The third order polynomial fitting process required includes two steps: use , found in Section 13.4, to calculate K1( , ) for each in Table 8; and, use the pair , K1( , ) in Table 8 to find the coefficients in Equation (32) that best fit these points. With Equation (32) calibrated, calculate K1 for each cycle by inputting calculated via Equation (28).

Table 8—Compiled K1( , ) and values for regression of K1. K1( , )

-0.5 0.4353-0.0368 0.0 0.4147-0.0352 0.2 0.4059-0.0348 0.4 0.3937-0.0338 0.6 0.3779-0.0325 0.8 0.3568-0.0307 1.0 0.3005-0.0259

(22)

<#> , for each cycle in Dataset 2 using Equation 23.¶

peak valley

peak valley

F F

F F

+=

+ (23)¶

12

where:¶Fpeak = peak axial force measured by the load transducer (kN or lb); and¶Fvalley = valley axial force measured by the load transducer (kN or lb).¶

<#>Compute the tension amplitude pseudo strain for each cycle in Dataset 2 using Equation 24.¶

1

2R Rta pp

+= (24)¶

<#>Dataset 2 by using Equation 25.¶

<#>( )

1cos

62.83bt−

= (25)¶

<#>in Dataset 2 by using Equation 26.¶

<#>( )

12 cos

62.83et−

−= (26)¶

Table 8

Table 8

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3 2

1 3 2 1 0( )K b b b bχ χ χ χ= × + × + × + (32)

where:

b0, b1, b2, b3 = fitting coefficients.

13.6.8.

13.6.8. Compute the average reduced time for each cycle in Dataset 3 using Equation (33).

1

10RT

Nt

a= (33)

where:

N = cycle number.

13.6.9. Reduce the number of data points in Dataset 3 by using a moving average data reduction filter. Use the filter ratios given in Table 9, applying Filter Ratio 1 for the first 10 percent of the loading cycles before failure and Filter Ratio 2 for the remaining loading cycles. The filter ratio is the data reduction rate of the chosen filter. For example, a filter ratio of 20 indicates that each group of 20 cycles are reduced to one data point.

Table 9—Filter Ratio values for different Nf ranges. Number of cycles to failure (Nf) Filter Ratio 1 Filter Ratio 2

Nf < 20000 10 100

20000 Nf < 50000 50 200

50000 Nf 100 200

13.6.10. Compute the change in damage, S, for each cycle in the Dataset 2 using Equation (34). Even with data reduction, a few sequential data points may have positive C values. A few of these spurious data points do not negatively affect the overall value of S, but they do complicate the calculation. An efficient method that accounts for these spurious data points is to use the piecewise function shown in Equation (34).

( ) ( ) ( ) ( )1 112

1 11 1 1

1

2

0

Rta n n R n n

n

n n

DMRC C t K C CS

C C

+

+ +− −

−

− ∗ − ∗ ∗ ≤ ∗=

∗ > ∗

(34)

where:

C*n = the cyclic pseudo secant modulus at the current analysis cycle; C*n–1 = the cyclic pseudo secant modulus at the previous analysis cycle; and

tR = the change in the average reduced time between analysis cycles.

13.6.11. Determine the damage at each analysis cycle using Equation (35).

Dataset11

N

n nn

S S S=

= + (35)

where:

SDataset1 = cumulative damage value at the end of Dataset 1; Sn = cumulative damage at the current analysis cycle; and

Sn = incremental damage for all analysis cycles to be summed from the initial analysis cycle step, n = 1, to the current time step, N.

<#>factor for each cycle in Dataset 2 using Equation 27. Equation 27 should be solved for each cycle, but generally does not change significantly after the first few cycles, and a constant value may be applied after this transient period. Values of K have been tabulated for typical values of and in Table 5.¶<#>¶<#>Table 4—Compiled K Values for Typical Material and Test Conditions¶<#>Beta

2

Equation 28.¶

(28)

<#>¶

Equation 29

¶Note 10—E

Equation 23

(29)¶

Equation 30

(30)

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13.7. Combine the damage and pseudo secant modulus from each time step in the first cycle, Sections 13.5.3 and 13.5.5, with the cyclic pseudo secant moduli and damage values from Sections 13.6.2 and 13.6.11, into a single dataset.

13.8. This section describes the steps necessary to fit a power law model to the damage characteristic curve.

13.8.1. Reduce the number of data points obtained in Section 13.7 using equal damage increments of approximately 5,000.

13.8.2. For each mixture, determine the fitting coefficients in Equation (36) using regression of the aggregated data from Section 13.8.1 for all successful fatigue tests.

12111 CC C S= − (36)

where:

C11, C12 = the fitting coefficients for the power model.

13.9. This section describes the steps necessary to calculate the DR value.

13.9.1. Calculate the summation of (1-C) for each test specimen according to Equation (37).

( ) ( ) 11

1 1 ( )fN

i i ii

Sum C C N N−

=

− = − × − (37)

where:

Ni = number of cycles in the i-th step;

Ci = integrity at cycle Ni; and

Nf = number of cycles to failure.

13.9.2. Calculate the slope of the line formed by the Sum (1 – C) and Nf using the results of all valid tests and forcing an intercept of zero. This slope is the DR value. Equation (38) provides a numerical solution to calculate the slope.

( )( )

( )

,1

2

, ,1

11

P

f jjjR

P

f j f jj

Sum C N

DP

N N

=

=

− ×

=

×

(38)

where:

Sum(1 – C)j = summation of (1 – C) for the j-th specimen, Equation (37);

Nf,j = number of cycles to failure for the j-th specimen; and

P = number of specimens.

14. REPORT

14.1. Report the following for each specimen tested:

14.1.1. Test temperature;

14.1.2. The fingerprint dynamic modulus, |E*| fingerprint;

14.1.3. The dynamic modulus ration (DMR) value; and

12.13 and 12.16

12.23 and 12.31

(37)

(38)

(37)

<#>For each mixture, determine the damage characteristic relationship by fitting one of the following equations to the plot of the pseudo secant modulus and damage from successful fatigue tests.¶

baSC e= or (31)¶

1 zC yS= − (32)¶

where:¶a, b = the fitting coefficients for the exponential model; and¶y, z = the fitting coefficients for the power model.¶Note 11—The coefficients k1, k2, and k3 can be fit using the Nf and

t for use in the AASHTOWare Pavement ME Design software with additional localized calibration coefficients.¶<#>Calculate the summation of (1 – C) for each specimen.¶

( ) ( )0

Sum 1 1fN

C C dN− = − (33)¶

where:¶Nf = cycles to failure¶<#>Determine the average reduction in pseudo secant modulus to failure by plotting the Sum (1 – C) term against the number of cycles to failure for each specimen and fitting a line through the origin. The average reduction in pseudo secant modulus, DR, is the slope of the fitted line.¶

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14.1.4. Sum(1 – C) and Nf for each test specimen.

14.2. Report the following for each mixture tested:

14.2.1. The model term related to the log-log slope of the storage modulus master curve, ;

14.2.2. damage characteristic curve (C versus S curve) coefficients (C11 and C12 in Equation (36)); and

14.2.3. pseudo energy-based fatigue failure criterion (DR).

15. KEYWORDS

15.1. AMPT; axial deformation; complex modulus; cyclic fatigue; damage characteristic curve; direct tension; DMR; dynamic modulus; failure cycle; fingerprint; modulus; phase angle; Prony coefficients; relaxation modulus; pseudo secant modulus; pseudo strain; specimen deformation; strain.

APPENDIXES

(Nonmandatory Information)

X1. PROCEDURE FOR DETERMINING THE ON-SPECIMEN STRAIN LEVEL

X1.1. This procedure is designed to determine a target on-specimen strain level that produces test lengths between 5,000 and 40,000 cycles. The procedure is based on analysis shown in Lee et al. (2019) and is shown schematically in the flow chart shown in Figure X1.

relaxation

a

b

in Equation 31 or y and z in Equation 32

; and

for each mixture

<#>.¶

described

in detail in Sections X1.3 through X1.5

83 of 141



Figure X1.1—Diagram of the Strain Level Determination Process

X1.2. The referenced strain levels throughout the procedure can be found in Table X1. For the dynamic modulus input, use the value of |E*|LVE calculated in Equation (17) based on the results of dynamic modulus testing, if available. If that value is not available, the fingerprint modulus of the first test specimen may be used.

Run First Test(Initial Strain Level)

Run Second Tes(Increased Strain

Level)

Check for setupinput, software, o

machine errors

Run Second Tes(Initial Strain Leve

Run Second Tes(Decreased Strai

Level)

Nf 1> 80,000

40,000 < Nf �1

< 80,000

Nf 1

< 5,000

5,000 < Nf �1

< 40,000

Equation 11

, however there may be discrepancy between fingerprint moduli of individual specimens due to specimen-to-specimen variability. Do not adjust the selected modulus value after the first acceptable test.

84 of 141



Table X1.1—Target On-Specimen Strain Levels

|E*| (MPa)

Initial Strain Level

(microstrain)

Decreased Strain Level (microstrain)

Increased Strain Level

(microstrain)

Double- Increased Strain

Level (microstrain)

Strain (microstrain)

First test; Second test if

5,000<Nf1<40,000

Second test if Nf1<5,000

Second test if 40,000<Nf1<80,000

Second test if Nf1>80,000

Adjust repeated very short or very

long tests

2500 1030 860 1200 1370 170 3000 950 790 1110 1270 160 3500 880 740 1020 1160 140 4000 820 680 960 1100 140 4500 760 630 890 1020 130 5000 710 590 830 950 120 5500 670 560 780 890 110 6000 630 520 740 850 110 6500 590 490 690 790 100 7000 550 450 650 750 100 7500 520 430 610 700 90 8000 490 400 580 670 90 8500 460 380 540 620 80 9000 440 360 520 600 80 9500 410 330 490 570 80

10000 390 320 460 530 70 10500 360 290 430 500 70 11000 340 270 410 480 70 11500 320 260 380 440 60 12000 300 240 360 420 60 12500 280 220 340 400 60 13000 270 220 320 370 50 13500 250 200 300 350 50 14000 230 180 280 330 50 14500 210 160 260 310 50 15000 200 160 240 280 40 15500 180 140 220 260 40 16000 170 130 210 250 40 16500 150 110 190 230 40 17000 140 100 180 220 40 17500 130 100 160 190 30 18000 110 80 140 170 30 18500 100 70 130 160 30 19000 90 60 120 150 30 19500 80 50 110 140 30 20000 60 30 90 120 30

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X1.3. First Test:

X1.3.1. Run the first test at the Initial Strain Level.

X1.4. Second Test:

X1.4.1. If the first test failed between 5,000 and 40,000 cycles, run the second test at the same input strain level as the first test. If the first test yielded a number of cycles to failure between 40,000 and 80,000 cycles, run the second test at the Increased Strain Level. If the first test yielded a number of cycles to failure less than 5,000 cycles, run the second test at the Decreased Strain Level.

X1.4.2. If the first test yields a number of cycles to failure greater than 80,000 cycles, check for operator errors or machine problems (i.e., correct inputs, proper tuning, etc.). If issues are identified, correct the issues, discard the first test data, and run another test at the strain level indicated in the Initial Strain Level column of Table X1. If no issues are identified, run the next test at the strain level indicated in the Double-Increased Strain Level column of Table X1. If subsequent tests are longer than 80,000 cycles, increase the strain by 2 x Strain for each subsequent test until the number of cycles to failure is less than 80,000 cycles.

X1.5. Third and Subsequent Tests:

X1.5.1. If the second test failed between 5,000 and 40,000 cycles, run the third and subsequent tests at the same strain level as the second test.

X1.5.2. If the first test failed between 5,000 and 40,000 cycles but the second test failed in less than 5,000 cycles, run the third test at the strain level indicated in the Initial Strain Level column of Table X1.

X1.5.3. If the first test failed after 5,000 cycles, and the second failed after more than 40,000 cycles, increase the strain level by Strain for subsequent tests until the number of cycles to failure is between 5,000 and 40,000.

X1.5.4. If both the first and second tests fail in less than 5,000 cycles, investigate the specimen fabrication, preparation, and installation processes to ensure the test specimens are not being damaged (e.g., test specimen carried by the top of the specimen or the top loading platen, attached to the machine unevenly, etc.). Correct any issues identified, discard previous test data, and rerun both tests. If no issues are found, reduce the strain level by Strain for subsequent tests, until a specimen fails within 5,000 and 40,000 cycles.

X1.5.5. If the first two tests have been run at the prescribed strain levels but one failed at a cycle greater than 40,000 cycles and the other failed at less than 5,000 cycles, rerun the test at the same strain level as the test that failed in less than 5,000 cycles because this early failure was an unexpected result. If the repeated test fails before 5,000 cycles, select a strain level between those used in the first and second tests.

X2. CALCULATING THE SAPP VALUE

X2.1. This section presents a standard procedure for calculating the Sapp parameter from the cyclic fatigue parameters measured in this protocol and the dynamic modulus, |E*( )|, measured according to AASHTO TP 133.

X2.2. Calculate the Sapp temperature using LTPPBind Online.

X2.2.1. Enter relevant project information into LTPPBind Online. Use the MERRA weather station selected from the LTPPBind Online map function and the following parameters; Target Rut Depth

¶|E*| (MPa)

yielded a number of cycles to failure

Initial Strain Level again

*

S

then continue to X1.4 for subsequent tests

yields

to failure

continue testing

for subsequent tests

yielded

to failure,

yielded

to failure

yielded greater than

to failure

test yields a number of cycles to failure greater

S

,

yield a number of cycles to failure

S

the number of cycles to failure is

between

,

yielded a number of cycles to failure

yielded

yielded

, as that is

the two levels previously evaluated

86 of 141



= 12.5 mm, Depth of Layer = 0 mm, Traffic Loading Cumulative ESAL for the Design Period, Millions = 0.1, and Traffic Speed = Fast.

X2.2.2. Extract the high and low performance temperatures, Thigh and Tlow, respectively, from the “Adjusted Performance Grade Temperature” row of the “AASHTO M320-17 Performance-Graded Asphalt Binder” table.

X2.2.3. Determine the climatic performance grade high temperature using Equation X2.1. 4.01

6 +106

highTHT floor

−= × (X2.1)

where:

HT = climatic performance grade high temperature;

Thigh = high temperature performance temperature extracted from Step X2.2.2; and

floor = floor function.

X2.2.4. Determine the climatic performance grade low temperature using Equation X2.2.

86 +8

6lowT

LT floor−

= × (X2.2)

where: LT = climatic performance grade low temperature; Tlow = low temperature performance temperature extracted from Step X1.2.2; and floor = floor function.

X2.2.5. Determine the Sapp temperature, T(Sapp), using Equation X2.3.

32Sapp

HT LTT

+= − (X2.3)

X2.3. Determine the reference modulus for Sapp calculation, |E*|LVE,Sapp.

X2.3.1. Calculate the shift factor at T(Sapp) using Equation X2.4.

( )( ) ( ) ( ) ( )2 2

1 2 1 1 22( ) 10 ref refap ref

app

p appa a aT T a T a TT

TS

S Sa

× + − × × × + × − ×

= (X2.4)

where: a1, a2 = fitting coefficients from Equation (5).

X2.3.2. Calculate the reduced frequency for the reference modulus using Equation X2.5.

( ) ( )62.8app appR S T Saω = × (X2.5)

X2.3.3. Calculate the reference modulus for Sapp by substituting the reduced frequency from Step X2.3.2 into Equation X2.6.

( )

( )

( )

( )

2 22 2

2 2 2 21 11 1

app app

app app

N Nm R m m R mS S

LVE ,SappR m R mm mS S

E EE * E

ω ρ ω ρ

ω ρ ω ρ∞

= =

= + ++ +

(X2.6)

where from Section 13.2.5: Em = modulus of Prony term number m, (kPa);

(5)

87 of 141



m = relaxation time of Prony term m (s); and n = number of Prony terms used.

X2.4. Compute Sapp using Equation X2.7.

12

11

1( )

1 112

* 4,

1000app

R C

T S

app

LVE Sapp

Da

CS

E

α

α

α

+

−

= (X2.7)

X3. USE OF ALTERNATIVE SMALL SPECIMEN GEOMETRIES

X3.1. Alternative Small Specimen Geometries—Test specimens of geometries other than the 38-mm (1.50-in.) diameter test specimen specified can be obtained from constructed pavement layers to measure fatigue properties for use in applications such as forensic investigations and field monitoring of test sections. Test specimens with a 50-mm (1.97-in.) diameter can be used where there are concerns about the use of 38-mm (1.50-in.) test specimens. Prismatic specimens that are 25 mm by 50 mm by 110 mm (0.98 in. by 1.97 in. by 4.33 in.) can be used for construction lifts thinner than 38 mm (1.50 in.).

X3.2. Alternative Small Specimen Geometry Test Equipment—The same gauge points, gauge length, and on-specimen deformation sensors as those used for 38-mm (1.50-in.) diameter cylindrical test specimens are used. Alternate loading platens should be designed or procured with a gluing surface to match the alternative specimen geometry. This may require custom adapters for the AMPT equipment. Any measurement given directly in units of force (i.e., seating load for securing the specimen) should be scaled to an equal-stress condition with the 38-mm (1.50-in.) test specimens.

1 This provisional standard was first published in 2019.

¶

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1.1.

1.2.

89 of 141

Date: March 19, 2020

To: Ross ‘Oak’ Metcalfe, P.E. AASHTO COMP Tech Section 2d Chair

WAQTC Executive Board Member State Materials Engineer Montana Department of Transportation [email protected]

From: John Bilderback, P.E. WAQTC Executive Board Chair State Construction & Materials Engineer Idaho Transportation Department [email protected]

Hi Oak,

Attached are revisions to T 312; Asphalt Mixture Specimens by Means of the Superpave Gyratory Compactor. The WAQTC believes these revisions are editorial; we hope you will concur.

It appears that in 2019, the title of this standard was revised to use the term ‘asphalt mixtures’ instead of ‘HMA’ but further revisions were not incorporated. To address this, WAQTC proposes the following revisions:

2. Referenced Documents – Change the reference to T 168 to R 97

4.4 – Change ‘binder’ and ‘HMA’ to ‘asphalt binder’ and ‘asphalt mixtures’

8. – Change HMA to ‘asphalt’

8.2.2 – Reference R 97 instead of T 168

8.2.5 – Change HMA to ‘asphalt mixtures’

Footer – Update the revision date

Thank you for your consideration. Let me know if you have any questions. JB/DAB/dab

90 of 141

AASHTO Designation: M 323-171

Technical Section: 2d, Proportioning of Asphalt–Aggregate Mixtures

Release: Group 3 (August 2017)


91 of 141

TS-2d M 323-1 AASHTO

Standard Specification for

AASHTO Designation: M 323-171

Technical Section: 2d, Proportioning of Asphalt–Aggregate Mixtures

Release: Group 3 (August 2017)

1. SCOPE

1.1. This specification for Superpave volumetric mix design uses aggregate and mixture properties to produce job-mix formulas for asphalt mixtures. It includes the original Superpave method in which design air voids are four percent and Superpave5 in which design air voids are five percent.

1.2. This standard specifies minimum quality requirements for binder, aggregate, and asphalt mixtures for Superpave volumetric mix designs.

1.3. This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety concerns associated with its use. It is the responsibility of the user of this procedure to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.



M 320, Performance-Graded Asphalt Binder

R 28, Accelerated Aging of Asphalt Binder Using a Pressurized Aging Vessel (PAV)

R 35, Superpave Volumetric Design for Asphalt Mixtures

R 59, Recovery of Asphalt Binder from Solution by Abson Method

T 11, Materials Finer Than 75-μm (No. 200) Sieve in Mineral Aggregates by Washing

T 27, Sieve Analysis of Fine and Coarse Aggregates

T 164, Quantitative Extraction of Asphalt Binder from Hot Mix Asphalt (HMA)

T 176, Plastic Fines in Graded Aggregates and Soils by Use of the Sand Equivalent Test

T 240, Effect of Heat and Air on a Moving Film of Asphalt Binder (Rolling Thin-Film Oven Test)


T 304, Uncompacted Void Content of Fine Aggregate

T 308, Determining the Asphalt Binder Content of Hot Mix Asphalt (HMA) by the Ignition Method


T 313, Determining the Flexural Creep Stiffness of Asphalt Binder Using the Bending Beam Rheometer (BBR)

•

92 of 141


T 315, Determining the Rheological Properties of Asphalt Binder Using a Dynamic Shear Rheometer (DSR)

T 319, Quantitative Extraction and Recovery of Asphalt Binder from Asphalt Mixtures

T 335, Determining the Percentage of Fracture in Coarse Aggregate

2.2. ASTM Standard:

D4791, Standard Test Method for Flat Particles, Elongated Particles, or Flat and Elongated Particles in Coarse Aggregate

2.3. Asphalt Institute Publication:

MS-2, Asphalt Mix Design Methods

2.4. National Asphalt Pavement Association Publication:

IS 128, HMA Pavement Mix Type Selection Guide

2.5. Other References:

LTPP Seasonal Asphalt Concrete Pavement Temperature Models. LTPPBind 3.1, http://ltpp-products.com/OtherProducts.asp

NCHRP Report 452: Recommended Use of Reclaimed Asphalt Pavement in the Superpave Mix Design Method: Technician’s Manual. National Cooperative Highway Research Program Project D9-12, TRB, National Research Council, Washington, DC, 2001.

3. TERMINOLOGY

3.1. air voids (Va)—the total volume of the small pockets of air between the coated aggregate particles throughout a compacted paving mixture, expressed as a percent of the bulk volume of the compacted paving mixture.

3.2. asphalt mixtures—includes hot mix and warm mix asphalt.

3.3. binder content (Pb) —the percent by mass of binder in the total mixture, including binder and aggregate.

3.4. binder content RAP (PbRAP) — the percent by mass of binder in the RAP based on total RAP, including binder and aggregate.

3.5. design ESALs—design equivalent (80-kN) single-axle loads.

Note 1— design ESALs are the anticipated project traffic level expected on the design lane over a 20-yr period. For pavements designed for more or less than 20 yr, determine the design ESALs for 20 yr when using this standard.

3.6. dust-to-binder ratio (P0.075/Pbe)—by mass, the ratio between the percent of aggregate passing the 75-μm (No. 200) sieve (P0.075) and the effective binder content (Pbe).

3.7. maximum aggregate size—one size larger than the nominal maximum aggregate size (Note 1).

Note 2—The definitions given in Sections 3.7 and 3.8 apply to Superpave mixtures only and differ from the definitions published in other AASHTO standards.

3.8. nominal maximum aggregate size—one size larger than the first sieve that retains more than 10 percent aggregate (Note 1).

•

¶

•

<#>discussion—design ESALs are the anticipated project traffic level expected on the design lane over a 20-yr period. For pavements designed for more or less than 20 yr, determine the design ESALs for 20 yr when using this standard.¶

1

93 of 141


3.9. primary control sieve (PCS)—the sieve defining the break point between fine- and coarse-graded mixtures for each nominal maximum aggregate size.

3.10. reagent-grade solvent—a solvent meeting the level of chemical purity as to conform to the specifications for “reagent grade” as established by the Committee on Analytical Reagents of the American Chemical Society and used to extract the asphalt binder from the mixture. When asphalt binder is intended to be extracted and then tested for additional properties, a reagent-grade solvent must be used. Non-reagent-grade solvents may contain epoxy resins that may affect the properties of the recovered binder. In particular, certain acid-modified binders may be affected by non-reagent grade solvents.

3.11. reclaimed asphalt pavement (RAP)—removed and/or processed pavement materials containing asphalt binder and aggregate.

3.12. reclaimed asphalt pavement binder ratio (RAPBR)—the ratio of the RAP binder in the mixture divided by the mixture’s total binder content.

3.13. voids in the mineral aggregate (VMA)—the volume of the intergranular void space between the aggregate particles of a compacted paving mixture that includes the air voids and the effective binder content, expressed as a percentage of the total volume of the specimen.

3.14. voids filled with asphalt (VFA)—the percentage of the VMA filled with binder (the effective binder volume divided by the VMA).


4.1. This standard may be used to select and evaluate materials for Superpave volumetric mix designs including the original Superpave and Superpave5. Unless otherwise noted, all sections apply to both versions of Superpave. Requirements for Superpave5 that differ from the original Superpave are specifically noted.

5. BINDER REQUIREMENTS

5.1. The binder shall be a performance-graded (PG) binder, meeting the requirements of M 320 or M 332, which is appropriate for the climate and traffic-loading conditions at the site of the paving project or as specified by the contract documents.

5.1.1. Determine the mean and the standard deviation of the yearly, 7-day-average, maximum pavement temperature, measured 20 mm below the pavement surface, and the mean and the standard deviation of the yearly, 1-day-minimum pavement temperature, measured at the pavement surface, at the site of the paving project. These temperatures can be determined by use of the LTPPBind software or can be supplied by the specifying agency. If the LTPPBind software is used, the LTPP high- and low-temperature models should be selected in the software when determining the binder grade. Often, actual site data are not available, and representative data from the appropriate weather station(s) will have to be used.

5.1.2. Select the design reliability for the high- and low-temperature performance desired. The design reliability required is established by agency policy.

Note 3—The selection of design reliability may be influenced by the initial cost of the materials and the subsequent maintenance costs.

5.1.3. Using the pavement temperature data determined, select the minimum required PG binder that satisfies the required design reliability.

•

•

3.1

•

nearest

2

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5.2. If the requirements of M 320 apply and the traffic speed or the design ESALs warrant, increase the high-temperature grade by the number of grade equivalents indicated in Table 1 to account for the anticipated traffic conditions at the project site. If the requirements of M 332 apply, follow those requirements for the appropriate binder selection.

Table 1—Binder Selection on the Basis of Traffic Speed and Traffic Level for M 320

Design ESALsb (Million)

Adjustment to the High-Temperature Grade of the Bindera Traffic Load Rate

Standardc Slowd Standinge <0.3 — — — f

0.3 to <3 — 1 2 3 to <10 — 1 2

10 to <30 — f 1 2

30 1 1 2 a Increase the high-temperature grade by the number of grade equivalents indicated (one grade is equivalent to 6˚C). Use the low-temperature grade as determined

in Section 5. b The anticipated project traffic level expected on the design lane over a 20-yr period. Regardless of the actual design life of the roadway, determine the design

ESALs for 20 yr. c Standard traffic—where the average traffic speed is greater than 70 km/h. d Slow traffic—where the average traffic speed ranges from 20 to 70 km/h. e Standing traffic—where the average traffic speed is less than 20 km/h. f Consideration should be given to increasing the high-temperature grade by one grade equivalent.

Note 4—Practically, PG binders stiffer than PG 82-xx should be avoided. In cases where the required adjustment to the high-temperature binder grade would result in a grade higher than a PG 82, consideration should be given to specifying a PG 82-xx and increasing the design ESALs by one level (e.g., 10 to <30 million increased to ≥30 million).

5.3. If RAP is to be used in the mixture, it is specified according to RAPBR.

5.3.1. The binder grade selected in Sections 5.1.3 and 5.2 must be adjusted to account for the amount and stiffness of the RAP binder. This adjustment shall be based on characterized properties of RAP asphalt binder either specific to a mix design or within a geographical area, as determined by the Agency. A process to develop binder selection adjustment requirements is given in Appendix X3.

Note 4

Table 2—Binder Selection Guidelines for Reclaimed Asphalt Pavement (RAP) Mixtures

Recommended Virgin Asphalt Binder Grade RAPBR No change in binder selection 0.25

Follow recommendations from Appendix X2 >0.25

( )

Total100RAP RAPPb P

RAPBRPb

×=

× (1)

where:

RAPBR = Reclaimed asphalt pavement binder ratio to nearest 0.01 PbRAP = Binder content of the RAP to nearest 0.1 PRAP = RAP percentage by weight of mixture to nearest 0.1

•

¶

3

may be

percent dry weight (mass) of the mixture or by reclaimed asphalt pavement binder ratio

•

<#>Percent dry weight (mass) of mixture—If the agency elects to use RAP adjustments by percent dry weight (mass) of the mixture, the binder grade selected in Sections 5.1.3 and 5.2 needs to be adjusted according to Table 2 to account for the amount and stiffness of the RAP binder. Procedures for developing a blending chart are included in Appendix X1.¶<#><#>Table 2—Binder Selection Guidelines for Reclaimed Asphalt Pavement (RAP) Mixtures

<#>¶<#>Recommended Virgin Asphalt Binder Grade

3

<

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PbTotal = Total binder content in the mixture to nearest 0.1

Note 5—A mixture performance test for cracking implemented by an agency is acceptable in lieu of the RAPBR binder selection criteria in Section 5.3.1.

6. COMBINED AGGREGATE REQUIREMENTS

6.1. Size Requirements:

6.1.1. Nominal Maximum Aggregate Size—The combined aggregate shall have a nominal maximum aggregate size of 4.75 to 19.0 mm for asphalt pavement surface courses and no larger than 37.5 mm for asphalt pavement subsurface courses.

Note 65—Additional guidance on selection of the appropriate nominal maximum aggregate size mixture can be found in the National Asphalt Pavement Association’s IS 128.

6.1.2. Gradation Control Points—The combined aggregate shall conform to the gradation requirements specified in Table 3 when tested according to T 11 and T 27.

Table 3—Aggregate Gradation Control Points

Nominal Maximum Aggregate Size—Control Points (% Passing)

Sieve Size, mm

37.5 mm 25.0 mm 19.0 mm 12.5 mm 9.5 mm 4.75 mm Min Max Min Max Min Max Min Max Min Max Min Max

50.0 100 — — — — — — — — — — —

37.5 90 100 100 — — — — — — — — —

25.0 — 90 90 100 100 — — — — — — —

19.0 — — — 90 90 100 100 — — — — —

12.5 — — — — — 90 90 100 100 — 100 —

9.5 — — — — — — — 90 90 100 95 100

4.75 — — — — — — — — — 90 90 100

2.36 15 41 19 45 23 49 28 58 32 67 — —

1.18 — — — — — — — — — — 30 55

0.075 0 6 1 7 2 8 2 10 2 10 6 13

6.1.3. Gradation Classification—The combined aggregate gradation shall be classified as coarse-graded when it passes below the Primary Control Sieve (PCS) control point as defined in Table 4 (also see Figure 1). All other gradations shall be classified as fine-graded.

Table 4—Gradation Classification

PCS Control Point for Mixture Nominal Maximum Aggregate Size (% Passing)

Nominal maximum aggregate size 37.5 mm 25.0 mm 19.0 mm 12.5 mm 9.5 mm 4.75

Primary control sieve 9.5 mm 4.75 mm 4.75 mm 2.36 mm 2.36 mm 1.18 mm

PCS control point, % passing 47 40 47 39 47 40

•

45

4

24

5

35

•

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Figure 1—Gradation Control Points for a 12.5-mm Nominal Maximum Aggregate Size Gradation

6.2. Coarse Aggregate Angularity Requirements—The aggregate shall meet the percentage of fractured faces requirements, specified in Table 5, measured according to T 335.

6.3. Fine Aggregate Angularity Requirements—The aggregate shall meet the uncompacted void content of fine aggregate requirements, specified in Table 5, measured according to T 304, Method A.

6.4. Sand Equivalent Requirements—The aggregate shall meet the sand equivalent (clay content) requirements, specified in Table 5, measured according to T 176.

6.5. Flat-and-Elongated Requirements—The aggregate shall meet the flat-and-elongated requirements, specified in Table 5, measured according to ASTM D4791, with the exception that the material passing the 9.5-mm sieve and retained on the 4.75-mm sieve shall be included. The aggregate shall be measured using the ratio of 5:1, comparing the length (longest dimension) to the thickness (smallest dimension) of the aggregate particles.

6.6. When RAP is used in the mixture, the RAP aggregate shall be extracted from the RAP using a solvent extraction (T 164) or ignition oven (T 308) as specified by the agency. The RAP aggregate shall be included in determinations of gradation, coarse aggregate angularity, fine aggregate angularity, and flat-and-elongated requirements. The sand equivalent requirements shall be waived for the RAP aggregate but shall apply to the remainder of the aggregate blend.

Table 5—Superpave and Superpave5 Aggregate Consensus Property Requirements

Design ESALsa

(Million)

Fractured Faces, Coarse Aggregate,c

% Minimum

Uncompacted Void Content of Fine Aggregate,

% Minimum Sand

Equivalent, % Minimum

Flat and Elongated,c

% Maximum Depth from Surface Depth from Surface

Maximum Density Line

Maximum Size

Nominal Maximum Size

PCS Control Point

75 μm 2.36 mm 9.5 mm 12.5 mm 19.0 mm

Sieve Opening (0.45 Power)

Perc

ent P

assin

g

0.0

20.0

40.0

60.0

80.0

100.00

Superpave

Size

6

6

6

6

6

•

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100 mm >100 mm 100 mm >100 mm <0.3 55/— —/— —d — 40 —

0.3 to <3 75/— 50/— 40 e 40 40 10

3 to <10 85/80b 60/— 45 40 45 10

10 to <30 95/90 80/75 45 40 45 10

30 100/100 100/100 45 45 50 10 a The anticipated project traffic level expected on the design lane over a 20-yr period. Regardless of the actual design life of the roadway, determine the design

ESALs for 20 yr. b 85/80 denotes that 85 percent of the coarse aggregate has one fractured face and 80 percent has two or more fractured faces. c This criterion does not apply to 4.75-mm nominal maximum size mixtures. d For 4.75-mm nominal maximum size mixtures designed for traffic levels below 0.3 million ESALs, the minimum Uncompacted Void Content is 40. e For 4.75-mm nominal maximum size mixtures designed for traffic levels equal to or above 0.3 million ESALs, the minimum Uncompacted Void Content is 45.

Note 8—If less than 25 percent of a construction lift is within 100 mm of the surface, the lift may be considered to be below 100 mm for mixture design purposes.

7. ASPHALT MIXTURE DESIGN REQUIREMENTS

7.1. The binder and aggregate in the asphalt mixture shall conform to the requirements of Sections 5 and 6.

7.2. When compacted in accordance with T 312, Superpave mixture design shall meet the relative density, VMA and dust-to-binder ratio requirements specified in Table 6 and the VFA requirements specified in Table 8. Superpave5 mixture design compacted in accordance with T 312 shall meet the relative density, VMA and dust-to-binder ratio requirements specified in Table 7 and the VFA requirements specified in Table 8. For both Superpave and Superpave5 the initial, design, and maximum number of gyrations are specified in R 35.

Table 6—Superpave Asphalt Mixture Design Requirements

Design ESALs,a

million

Required Relative Density, Percent of Theoretical

Maximum Specific Gravity Voids in the Mineral Aggregate (VMA),

% Minimum Dust-to-Binder Ratio

Rangec Ninitial Ndesignb Nmax

Nominal Maximum Aggregate Size, mm

37.5 25.0 19.0 12.5 9.5 4.75 <0.3 91.5 96.0 98.0 11.0 12.0 13.0 14.0 15.0 16.0 0.6–1.2

0.3 to <3 90.5 96.0 98.0 11.0 12.0 13.0 14.0 15.0 16.0 0.6–1.2

3 to <10 89.0 96.0 98.0 11.0 12.0 13.0 14.0 15.0 16.0 0.6–1.2

10 to <30 89.0 96.0 98.0 11.0 12.0 13.0 14.0 15.0 16.0 0.6–1.2

30 89.0 96.0 98.0 11.0 12.0 13.0 14.0 15.0 16.0 0.6–1.2 a Design ESALs are the anticipated project traffic level expected on the design lane over a 20-yr period. Regardless of the actual design life of the roadway,

determine the design ESALs for 20 yr. b For 4.75-mm nominal maximum size mixtures, the relative density (as a percent of the theoretical maximum specific gravity) shall be within the range of 94.0 to

96.0 percent. c For 4.75-mm nominal maximum size mixtures, the dust-to-binder ratio shall be 1.0 to 2.0, for design traffic levels <3 million ESALs, and 1.5 to 2.0 for design

traffic levels 3 million ESALs.

6

The asphalt mixture design, when

, VFA,

7

T

•

7

•

Rangec

d

c

b For 37.5-mm nominal maximum size mixtures, the specified lower limit of the VFA range shall be 64 percent for all design traffic levels.¶c

For 4.75-mm nominal maximum size mixtures, the dust-to-binder ratio shall be 1.0 to 2.0, for design traffic levels <3 million ESALs, and 1.5 to 2.0 for design traffic levels 3 million ESALs.

d

For 4.75-mm nominal maximum size mixtures, the relative density (as a percent of the theoretical maximum specific gravity) shall be within the range of 94.0 to 96.0 percent.

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Table 7—Superpave5 Asphalt Mixture Design Requirements

Design ESALs,a

million

Required Relative Density, Percent of Theoretical

Maximum Specific Gravity Voids in the Mineral Aggregate (VMA),

% Minimum Dust-to-Binder Ratio

Rangec Ninitial Ndesignb Nmax

Nominal Maximum Aggregate Size, mm

37.5 25.0 19.0 12.5 9.5 4.75 <0.3 91.5 95.0 97.0 12.0 13.0 14.0 15.0 16.0 17.0 0.6–1.2

0.3 to <3 90.5 95.0 97.0 12.0 13.0 14.0 15.0 16.0 17.0 0.6–1.2

3 to <10 89.0 95.0 97.0 12.0 13.0 14.0 15.0 16.0 17.0 0.6–1.2

10 to <30 89.0 95.0 97.0 12.0 13.0 14.0 15.0 16.0 17.0 0.6–1.2

30 89.0 95.0 97.0 12.0 13.0 14.0 15.0 16.0 17.0 0.6–1.2 a Design ESALs are the anticipated project traffic level expected on the design lane over a 20-yr period. Regardless of the actual design life of the roadway,

determine the design ESALs for 20 yr. b For 4.75-mm nominal maximum size mixtures, the relative density (as a percent of the theoretical maximum specific gravity) shall be within the range of 94.0 to

96.0 percent. c For 4.75-mm nominal maximum size mixtures, the dust-to-binder ratio shall be 1.0 to 2.0, for design traffic levels <3 million ESALs, and 1.5 to 2.0 for design

traffic levels 3 million ESALs.

Table 8—Voids Filled with Asphalt for Superpave and Superpave5

Mixture NMAS

Superpave Superpave5

Minimum Maximum Minimum Maximum 37.5 64 69 58 64

25.0 67 71 62 67

19.0 69 73 64 69

12.5 71 75 67 71

9.5 73 76 69 72

4.75 63 78 65 79

Note 9—If the aggregate gradation passes beneath the PCS Control Point specified in Table 4, the dust-to-binder ratio range may be increased from 0.6–1.2 to 0.8–1.6 at the agency’s discretion.

Note 10—Mixtures with VMA exceeding the minimum value by more than 2 percent may be prone to flushing and rutting. Unless satisfactory experience with high VMA mixtures is available, mixtures with VMA greater than 2 percent above the minimum should be avoided.

7.3. For both Superpave and Superpave5 asphalt mixture design, the mixture when compacted according to T 312 at 7.0 ± 0.5 percent air voids and tested in accordance with T 283, shall have a minimum tensile strength ratio of 0.80.

8. KEYWORDS

8.1. Aggregate and mixture properties; job mix formulas; Superpave; volumetric mix design.

9. REFERENCE

9.1. NCHRP. NCHRP Report 752: Improved Mix Design, Evaluation, and Materials Management Practices for Hot Mix Asphalt with High Reclaimed Asphalt Pavement Content. National

e For design traffic levels <0.3 million ESALs, and for 25.0-mm nominal maximum size mixtures, the specified lower limit of the VFA range shall be 67 percent, and for 4.75-mm nominal maximum size mixtures, the specified VFA range shall be 67 to 79 percent.¶f For design traffic levels >0.3 million ESALs, and for 4.75-mm nominal maximum size mixtures, the specified VFA range shall be 66 to 77 percent.¶g For design traffic levels 3 million ESALs, and for 9.5-mm nominal maximum size mixtures, the specified VFA range shall be 73 to 76 percent.¶

•

d

c

b For 37.5-mm nominal maximum size mixtures, the specified lower limit of the VFA range shall be 64 percent for all design traffic levels.¶

c

d

•

•

•

f For design traffic levels >0.3 million ESALs, and for 4.75-mm nominal maximum size mixtures, the specified VFA range shall be 66 to 77 percent.¶

7

5

8

The

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Cooperative Highway Research Program Project 9-46, TRB, National Research Council, Washington, DC, 2013.

APPENDIXES


X1. PROCEDURES FOR DEVELOPING A BLENDING CHART

X1.1. Blending of RAP binders can be accomplished by knowing the desired final grade (critical temperature) of the blended binder, the physical properties (and critical temperatures) of the recovered RAP binder, and either the physical properties (and critical temperatures) of the virgin asphalt binder or the desired percentage of RAP in the mixture.

X1.2. Determine the physical properties and critical temperatures of the RAP binder:

X1.2.1.

Note X1—While T 319 is the preferred method, at the discretion of the agency, R 59 may be used. Research conducted under NCHRP 9-12 (NCHRP Report 452) indicated that R 59 might affect recovered binder properties.

X1.2.2.

X1.2.2.1.

a = log(G*/sin )/ T (X1.1)

X1.2.2.2. °

1 1

log(1.00) log( )(High)c

GT T

a

−= + (X1.2)

where:

G1 = the G*/sin value at a specific temperature T1; and

a = the slope as described in Equation X1.1.

Note X2—Although any temperature (T1) and the corresponding stiffness (G1) can be selected, it is advisable to use the G*/sin value closest to the criterion (1.00 kPa) to minimize extrapolation errors.

X1.2.3.

100 of 141


X1.2.4.

X1.2.4.1.

a = log(G*/sin )/ T (X1.3)

X1.2.4.2. °

11

log(2.20) log( )(High)c

GT T

a

−= + (X1.4)

where:




X1.2.5.

X1.2.6.

X1.2.6.1.

a = log(G*/sin )/ T (X1.5)

X1.2.6.2. °

11

log(5000) log( )( )c

GT Int T

a

−= + (X1.6)

where:



Note X4—Although any temperature (T1) and the corresponding stiffness (G1) can be selected, it is advisable to use the G*/sin value closest to the criterion (5000 kPa) to minimize extrapolation errors.

X1.2.7.

X1.2.7.1.

101 of 141


a = log(S)/ T (X1.7)

X1.2.7.2. °

11

log(300) log( )( )c

ST S T

a

−= + (X1.8)

where:

S1 = the S-value at a specific temperature T1; and


Note X5—Although any temperature (T1) and the corresponding stiffness (S1) can be selected, it is advisable to use the S-value closest to the criterion (300 MPa) to minimize extrapolation errors.

X1.2.7.3.

a = m-value/ T (X1.9)

X1.2.7.4. °

11

0.300( )c

mT m T

a

−= + (X1.10)

where:

m1 = the m-value at a specific temperature T1; and


Note X6—Although any temperature (T1) and the corresponding m-value (m1) can be selected, it is advisable to use the m-value closest to the criterion (0.300) to minimize extrapolation errors.

X1.2.7.5.

X1.2.8.

X1.3. Blending at a Known RAP Percentage:

X1.3.1.

X1.3.1.1.

blend RAPvirgin

(%RAP )

(1 %RAP)

T TT

− ×=

− (X1.11)

where:

102 of 141


Tvirgin = critical temperature of virgin asphalt binder (high, intermediate, or low); Tblend = critical temperature of blended asphalt binder (final desired) (high, intermediate, or

low); %RAP = percentage of RAP expressed as a decimal to nearest 0.001; and TRAP = critical temperature of recovered RAP binder (high, intermediate, or low).

X1.3.1.2.

X1.4. Blending with a Known Virgin Binder:

X1.4.1.

X1.4.1.1.

blend virgin

RAP virgin

%RAPT T

T T

−=

− (X1.12)

where:

%RAP = percentage of RAP expressed as a decimal to nearest 0.001; Tvirgin = critical temperature of virgin asphalt binder (high, intermediate, or low); Tblend = critical temperature of blended asphalt binder (high, intermediate, or low);

andTRAP = critical temperature of recovered RAP binder (high, intermediate, or low).

X1.4.1.2.

X2. PROCEDURES FOR ESTIMATING THE PROPERTIES OF BLENDED RAP AND VIRGIN BINDERS

X2.1. Selection of the appropriate grade of virgin binder for mixtures with RAP binder ratios 0.25 can be based on knowledge of the true grade of the RAP binder, the high and low critical temperatures for the project location and pavement layer, and either the approximate RAP binder ratio or the high and low critical temperatures for the available virgin binder(s).

Note X7—The high and low critical temperatures for a project location and pavement layer can be determined using the latest version of LTPPBind.

Note X8—Agencies may elect to establish typical RAP binder properties for specific geographic areas based on testing and analysis of RAP binders from numerous stockpiles within each area. Detailed procedures on the geographic RAP evaluation are contained in Appendix X3.

X2.2. Determine the physical properties and critical temperatures of the RAP binder:

X2.2.1.

Note X9—While T 319 is the preferred method, at the discretion of the agency, R 59 may be used. Research conducted under NCHRP 9-12 indicated that R 59 might affect recovered binder properties.

¶

103 of 141


X2.2.2.

X2.2.2.1. *

logsinG

aT

Δδ

=Δ

(X2.1)

X2.2.2.2. °

( )( ) ( )1

1log 1.00 log

HighcG

T Ta

−= + (X2.2)

where:

G1 = the G*/sin value at a specific temperature;

a = the slope as described in Equation X2.1; and

T1 = specific temperature.


X2.2.3.

X2.2.4.

X2.2.4.1. *

logsinG

aT

Δδ

=Δ

(X2.3)

Determine Tc (High) based on RTFO DSR, to the nearest 0.1°C using the following equation:

( )( ) ( )1

1log 2.20 log

HighcG

T Ta

−= + (X2.4)

where:

G1 = the G*/sin value at a specific temperature;




X2.2.5.

104 of 141


X2.2.6.

X2.2.6.1. *

logsin

G

aT

Δδ

=Δ

(X2.5)

X2.2.6.2. °

( )( ) ( )1

1log 5000 log

cG

T Int Ta

−= + (X2.6)

where:

Tc (Int) = critical intermediate temperature with PAV aged RAP binder; G1 = the G*/sin value at a specific temperature; a = the slope as described in Equation X2.5; and T1 = specific temperature.

Note X12—Although any specific temperature (T1) and the corresponding stiffness (G1) can be selected, it is advisable to use the G*/sin value closest to the criterion (5000 kPa) to minimize extrapolation errors.

X2.2.7.

X2.2.7.1. ( )log S

aT

Δ=

Δ (X2.7)

X2.2.7.2. °

( )( ) ( )1

1log 300 log

cS

T S Ta

−= + (X2.8)

where:

S1 = the S-value at a specific temperature T1;



Note X13—Although any specific temperature (T1) and the corresponding stiffness (S1) can be selected, it is advisable to use the S-value closest to the criterion (300 MPa) to minimize extrapolation errors.

X2.2.7.3. ( )-valuem

aT

Δ=

Δ (X2.9)

X2.2.7.4. °

( ) 11

0.300c

mT m T

a

−= + (X2.10)

105 of 141


where:

Tc (m) = critical temperature for the m-value; m1 = the m-value at a specific temperature; a = the slope as described in Equation X2.9; and T1 = specific temperature.

Note X14—Although any specific temperature (T1) and the corresponding m-value (m1) can be selected, it is advisable to use the m-value closest to the criterion (0.300) to minimize extrapolation errors.

X2.2.7.5.

X2.2.8.

X2.3. Determination of the appropriate virgin binder grade using an approximate RAPBR:

X2.3.1.

X2.3.1.1.

( )( ) ( )

( )

need Bindervirgin

1c c

c

T RAPBR T RAPT

RAPBR

− ×=

− (X2.11)

X2.3.1.2.

X2.4. Blending with a Known Virgin Binder:

X2.4.1.

RAP binder ratio

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X2.4.1.1. ( ) ( )

( ) ( )max

need virgin

Binder virginc c

c c

T TRAPBR

T RAP T

−=

− (X2.12)

X2.4.1.2.

X3. PROCEDURES FOR EVALUATING RAP STOCKPILES

X3.1. The purpose of this appendix is to characterize properties of RAP asphalt binder within a geographical area to determine the appropriate percentages of RAP at which virgin asphalt binder properties should be changed for that geographical area.

X3.2. RAP stockpile locations should be selected throughout the geographical area. Geographical areas should be selected with consideration to climatic zones and material sources. The number of stockpile locations may depend on the size of the geographical area, variability of climate, and other factors within the area.

X3.3. Evaluation of the physical properties of the recovered RAP binder begins with the sampling and testing of the stockpiles within the geographical area. Samples should be large enough to provide enough extracted asphalt binder for PG grading and evaluation of the results.

X3.4. In locations where RAP containing different binders such as polymer-modified grades is stockpiled separately, evaluation of the RAP asphalt binder should be performed separately from other stockpiles.

X3.5. Solvent extractions shall be performed on the RAP samples in accordance with T 319 to acquire recovered binder samples.

X3.6. Determine the physical properties and critical failure temperatures of the RAP binders as outlined in Appendix X1.

X3.7. In some cases the high-temperature grade of the recovered binder may be higher than the temperature range of the DSR equipment. For these cases, the binder should be tested at three temperatures: –3, –9, and –15°C from the high temperature limit of the equipment. Plot the log of the test temperature versus the log of the binder property to project the temperature at which the binder will meet the grade requirements. All binder grading should be performed to provide the actual continuous grades of the RAP binder.

A reagent-grade solvent is required when asphalt binder is extracted and tested for additional properties

.

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X3.8. Determine the distribution of RAP binder grades from stockpiles within the geographical area of study. From the distribution of temperature grades, calculate the average continuous high and low temperature grades from the RAP stockpiles. The average low-temperature grade adjusted by two standard deviations warmer will provide 98 percent reliability for the low temperature grade of RAP binders in the geographical area of study.

X3.9. Collect multiple samples of asphalt binder for each grade supplied into the geographical area of study. Determine the continuous high and low temperature grade for each binder. The average low-temperature grade adjusted by two standard deviations warmer will provide 98 percent reliability for the warmest low-temperature grade being provided into the geographical area. .

X3.10. Perform a blending analysis using Section X1.4 to determine the maximum allowable percent of RAP binder to be added to a virgin asphalt binder to meet the low-temperature grade according to the LTPPBind software.

Note X15—For example, PG xx-22 may be specified; however, a RAP blend that produces a PG xx-16 may provide 98 percent reliability according to the LTPPBind software. In most cases, reliabilities of less than 98 percent are acceptable and will result in only minor temperature differences.

X3.11. Evaluation of asphalt binder recovered from RAP stockpiles in a typical geographical area may provide the necessary information to establish the maximum RAP binder replacement for a given virgin binder grade in the area. This information can be used to establish design criteria within a specific geographical area. In areas where the recovered RAP binder properties vary significantly, a general RAP percentage may not be appropriate. In these cases, the analysis should be performed on a project-by-project basis. Reevaluation of the analysis of the maximum asphalt binder replacement amounts should be completed periodically to address changes in the binders for any given geographical area.

1 Formerly AASHTO Provisional Standard MP 2. First published as a full standard in 2004.

plus

96

the

s

plus

96

of the virgin binders in

Use the highest or the 96 98 percent reliability continuous temperature grade in the blending analysis

3.1

3.1

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•

•

•

•

109 of 141

AASHTO Designation: R 35-171




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TS-2d R 35-1 AASHTO

Standard Practice for

AASHTO Designation: R 35-171



1. SCOPE

1.1. This standard practice for mix design evaluation uses aggregate and mixture properties to produce a hot mix asphalt (HMA) job mix formula. The mix design is based on the volumetric properties of the asphalt mixture in terms of the air voids, voids in the mineral aggregate (VMA), and voids filled with asphalt (VFA).

1.2. This standard practice may also be used to provide a preliminary selection of mix parameters as a starting point for mix analysis and performance prediction analyses that primarily use T 320 and T 322.

1.3. Special mixture design considerations and practices to be used in conjunction with this standard practice for the volumetric design of Warm Mix Asphalt (WMA) are given in Appendix X2.

1.4. This standard practice may involve hazardous materials, operations, and equipment. This standard practice does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this procedure to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.



M 320, Performance-Graded Asphalt Binder

M 323, Superpave Volumetric Mix Design

R 30, Mixture Conditioning of Hot Mix Asphalt (HMA)

R 76, Reducing Samples of Aggregate to Testing Size

R 83, Preparation of Cylindrical Performance Test Specimens Using the Superpave Gyratory Compactor (SGC)

R 90, Sampling Aggregate Products

T 11, Materials Finer Than 75- m (No. 200) Sieve in Mineral Aggregates by Washing

T 27, Sieve Analysis of Fine and Coarse Aggregates

T 84, Specific Gravity and Absorption of Fine Aggregate

T 85, Specific Gravity and Absorption of Coarse Aggregate

T 100, Specific Gravity of Soils

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TS-2d R 35-2 AASHTO


T 195, Determining Degree of Particle Coating of Asphalt Mixtures


T 228, Specific Gravity of Semi-Solid Asphalt Materials

T 275, Bulk Specific Gravity (Gmb) of Compacted Asphalt Mixtures Using Paraffin-Coated Specimens



T 320, Determining the Permanent Shear Strain and Stiffness of Asphalt Mixtures Using the Superpave Shear Tester (SST)

T 322, Determining the Creep Compliance and Strength of Hot Mix Asphalt (HMA) Using the Indirect Tensile Test Device

T 324, Hamburg Wheel-Track Testing of Compacted Asphalt Mixtures

T 378, Determining the Dynamic Modulus and Flow Number for Asphalt Mixtures Using the Asphalt Mixture Performance Tester (AMPT)

2.2. Asphalt Institute Standard:

SP-2, Superpave Mix Design

2.3. Other References:

LTPP Seasonal Asphalt Concrete Pavement Temperature Models, LTPPBind 3.1, http://www.ltppbind.com

NCHRP Report 567: Volumetric Requirements for Superpave Mix Design

3. TERMINOLOGY

3.1. absorbed binder volume (Vba)—the volume of binder absorbed into the aggregate (equal to the difference in aggregate volume when calculated with the bulk specific gravity and effective specific gravity).

3.2. air voids (Va)—the total volume of the small pockets of air between the coated aggregate particles throughout a compacted paving mixture, expressed as a percent of the bulk volume of the compacted paving mixture (Note 1).

Note 1—Term defined in Asphalt Institute Manual SP-2, Superpave Mix Design.

3.3. binder content (Pb)—the percent by mass of binder in the total mixture, including binder and aggregate.

3.4. design ESALs—design equivalent (80 kN) single-axle loads.

3.4.1. discussion—design ESALs are the anticipated project traffic level expected on the design lane over a 20-year period. For pavements designed for more or less than 20 years, determine the design ESALs for 20 years when using this standard practice.

3.5. dust-to-binder ratio (P0.075/Pbe)—by mass, the ratio between the percent passing the 75- m (No. 200) sieve (P0.075) and the effective binder content (Pbe).

3.6. effective binder volume (Vbe)—the volume of binder that is not absorbed into the aggregate.

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TS-2d R 35-3 AASHTO

3.7. HMA—hot mix asphalt.

3.8. maximum aggregate size—one size larger than the nominal maximum aggregate size (Note 2).

Note 2—The definitions given in Sections 3.10 and 3.11 apply to Superpave mixes only and differ from the definitions published in other AASHTO standards.

3.9. nominal maximum aggregate size—one size larger than the first sieve that retains more than 10 percent aggregate (Note 2).

3.10. primary control sieve (PCS)—the sieve defining the break point between fine and coarse-graded mixtures for each nominal maximum aggregate size.

3.11. reclaimed asphalt pavement (RAP)—removed and/or processed pavement materials containing asphalt binder and aggregate.

3.12. voids filled with asphalt (VFA)—the percentage of the VMA filled with binder (the effective binder volume divided by the VMA).

3.13. voids in the mineral aggregate (VMA)—the volume of the intergranular void space between the aggregate particles of a compacted paving mixture that includes the air voids and the effective binder content, expressed as a percent of the total volume of the specimen (Note 1).Summary of the Practice

3.14. Materials Selection—Binder, aggregate, and RAP stockpiles are selected that meet the environmental and traffic requirements applicable to the paving project. The bulk specific gravity of all aggregates proposed for blending and the specific gravity of the binder are determined.

Note 3—If RAP is used, the bulk specific gravity of the RAP aggregate may be estimated by determining the theoretical maximum specific gravity (Gmm) of the RAP mixture and using an assumed asphalt absorption for the RAP aggregate to back-calculate the RAP aggregate bulk specific gravity, if the absorption can be estimated with confidence. The RAP aggregate effective specific gravity may be used in lieu of the bulk specific gravity at the discretion of the agency. The use of the effective specific gravity may introduce an error into the combined aggregate bulk specific gravity and subsequent VMA calculations. The agency may choose to specify adjustments to the VMA requirements to account for this error based on experience with local aggregates.

3.15. Design Aggregate Structure—It is recommended that at least three trial aggregate blend gradations from selected aggregate stockpiles are blended. For each trial gradation, an initial trial binder content is determined, and at least two specimens are compacted in accordance with T 312. A design aggregate structure and an estimated design binder content are selected on the basis of satisfactory conformance of a trial gradation meeting the requirements given in M 323 for Va, VMA, VFA, dust-to-binder ratio at Ndesign, and relative density at Ninitial.

Note 4—Previous Superpave mix design experience with specific aggregate blends may eliminate the need for three trial blends.

3.16. Design Binder Content Selection—Replicate specimens are compacted in accordance with T 312 at the estimated design binder content and at the estimated design binder content ±0.5 percent and +1.0 percent. The design binder content is selected on the basis of satisfactory conformance with the requirements of M 323 for Va, VMA, VFA, and dust-to-binder ratio at Ndesign, and the relative density at Ninitial and Nmax.

3.17. Evaluating Moisture Susceptibility—Evaluate the moisture susceptibility of the design aggregate structure at the design binder content. Oven-condition the mixture according to T 283 Section 6. Compact specimens to 7.0 ± 0.5 percent air voids according to T 312. Group, moisture-condition, test, and evaluate specimens according to T 283. The design shall meet the tensile strength ratio requirement of M 323.

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TS-2d R 35-4 AASHTO

4. SUMMARY OF THE PRACTICE

4.1. Materials Selection—Binder, aggregate, and RAP stockpiles are selected that meet the environmental and traffic requirements applicable to the paving project. The bulk specific gravity of all aggregates proposed for blending and the specific gravity of the binder are determined.

Note 5—If RAP is used, the bulk specific gravity of the RAP aggregate may be estimated by determining the theoretical maximum specific gravity (Gmm) of the RAP mixture and using an assumed asphalt absorption for the RAP aggregate to back-calculate the RAP aggregate bulk specific gravity, if the absorption can be estimated with confidence. The RAP aggregate effective specific gravity may be used in lieu of the bulk specific gravity at the discretion of the agency. The use of the effective specific gravity may introduce an error into the combined aggregate bulk specific gravity and subsequent VMA calculations. The agency may choose to specify adjustments to the VMA requirements to account for this error based on experience with local aggregates.

4.2. Design Aggregate Structure—It is recommended that at least three trial aggregate blend gradations from selected aggregate stockpiles are blended. For each trial gradation, an initial trial binder content is determined, and at least two specimens are compacted in accordance with T 312. A design aggregate structure and an estimated design binder content are selected on the basis of satisfactory conformance of a trial gradation meeting the requirements given in M 323 for Va, VMA, VFA, dust-to-binder ratio at Ndesign, and relative density at Ninitial.

Note 6—Previous Superpave mix design experience with specific aggregate blends may eliminate the need for three trial blends.

4.3. Design Binder Content Selection—Replicate specimens are compacted in accordance with T 312 at the estimated design binder content and at the estimated design binder content ±0.5 percent and +1.0 percent. The design binder content is selected on the basis of satisfactory conformance with the requirements of M 323 for Va, VMA, VFA, and dust-to-binder ratio at Ndesign, and the relative density at Ninitial and Nmax.

4.4. Evaluating Moisture Susceptibility—Evaluate the moisture susceptibility of the design aggregate structure at the design binder content. Oven-condition the mixture according to T 283 Section 6. Compact specimens to 7.0 ± 0.5 percent air voids according to T 312. Group, moisture-condition, test, and evaluate specimens according to T 283. The design shall meet the tensile strength ratio requirement of M 323.


5.1. The procedure described in this standard practice is used to produce asphalt mixtures that satisfy Superpave asphalt volumetric mix design requirements. It includes the original Superpave method in which design air voids are four percent and Superpave5 in which design air voids are five percent.

6. PREPARING AGGREGATE TRIAL BLEND GRADATIONS

6.1. Select a binder in accordance with the requirements of M 323 and 320.

6.2. Determine the specific gravity of the binder according to T 228.

6.3. Obtain samples of aggregates proposed to be used for the project from the aggregate stockpiles in accordance with R 90.

3

4

A sentence adds Superpave5 to R 35. Rationale: The changes throughout are to update R 35 to include Superpave5.

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TS-2d R 35-5 AASHTO

Note 7—Each stockpile usually contains a given size of an aggregate fraction. Most projects employ three to five stockpiles to generate a combined gradation conforming to the job-mix formula and M 323.

6.4. Reduce the samples of aggregate fractions according to R 76 to samples of the size specified in T 27.

6.5. Wash and grade each aggregate sample according to T 11 and T 27 for the purpose of materials characterization of the aggregates.

6.6. Determine the bulk and apparent specific gravity for each coarse and fine aggregate fraction in accordance with T 85 and T 84, respectively, and determine the specific gravity of the mineral filler in accordance with T 100.

6.7. Blend the aggregate fractions for design purposes using Equation 1:

P = Aa + Bb + Cc, etc. (1)

where: P = percentage of material passing a given sieve for the combined aggregates A, B,

C, etc.; A, B, C, etc. = percentage of material passing a given sieve for aggregates A, B, C, etc.; and a, b, c, etc. = proportions of aggregates A, B, C, etc., used in the combination, and where the

total = 1.00.

6.8. Prepare a minimum of three trial aggregate blend gradations; plot the gradation of each trial blend on a 0.45-power gradation analysis chart, and confirm that each trial blend meets M 323 gradation controls (see Table 4 of M 323). Gradation control is based on four control sieve sizes: the sieve for the maximum aggregate size, the sieve for the nominal maximum aggregate size, the 4.75- or 2.36-mm sieve, and the 0.075-mm sieve. An example of three acceptable trial blends in the form of a gradation plot is given in Figure 1.

Figure 1—Evaluation of the Gradations of Three Trial Blends (Example)

5

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TS-2d R 35-6 AASHTO

6.9. Obtain a test specimen from each of the trial blends according to R 76, and conduct the quality tests specified in Section 6 of M 323 to confirm that the aggregate in the trial blends meets the minimum quality requirements specified in M 323.

Note 8—The designer has an option of performing the quality tests on each stockpile instead of the trial aggregate blend. The test results from each stockpile can be used to estimate the results for a given combination of materials.

7. DETERMINING AN INITIAL TRIAL BINDER CONTENT FOR EACH TRIAL AGGREGATE GRADATION

7.1. Designers can either use their experience with the materials or the procedure given in Appendix X1 to determine an initial trial binder content for each trial aggregate blend gradation.

Note 9—When using RAP, the initial trial asphalt content should be reduced by an amount equal to that provided by the RAP.

8. COMPACTING SPECIMENS OF EACH TRIAL GRADATION

8.1. Prepare replicate mixtures (Note 8) at the initial trial binder content for each of the chosen trial aggregate trial blend gradations. For Superpave mixtures determine the number of gyrations in Table 1 based on the design ESALs for the project. For Superpave5 mixtures determine the number of gyrations in Table 2.

Note 10—At least two replicate specimens are required, but three or more may be prepared if desired. Generally, 4500 to 4700 g of aggregate is sufficient for each compacted specimen with a height of 110 to 120 mm for aggregates with combined bulk specific gravities of 2.55 to 2.70, respectively.

8.2. Condition the mixtures according to R 30, and compact the specimens to Ndesign gyrations in accordance with T 312. Record the specimen height to the nearest 0.1 mm after each revolution.

8.3. Determine the bulk specific gravity (Gmb) of each of the compacted specimens in accordance with T 166 or T 275 as appropriate.

Table 1—Superpave Gyratory Compaction Effort

Design ESALsa

(Million) Compaction Parameters

Typical Roadway Applicationb Ninitial Ndesign Nmax <0.3 6 50 75 Applications include roadways with very light traffic volumes,

such as local roads, county roads, and city streets where truck traffic is prohibited or at a very minimal level. Traffic on these roadways would be considered local in nature, not regional, intrastate, or interstate. Special purpose roadways serving recreational sites or areas may also be applicable to this level.

0.3 to <3 7 75 115 Applications include many collector roads or access streets. Medium-trafficked city streets and the majority of county roadways may be applicable to this level.

3 to <30 8 100 160 Applications include many two-lane, multilane, divided, and partially or completely controlled access roadways. Among these are medium to highly trafficked city streets, many state routes, U.S. highways, and some rural Interstates.

30 9 125 205 Applications include the vast majority of the U.S. Interstate system, both rural and urban in nature. Special applications such as truck-weighing stations or truck-climbing lanes on two-lane roadways may also be applicable to this level.

a The anticipated project traffic level expected on the design lane over a 20-year period. Regardless of the actual design life of the roadway, determine the design ESALs for 20 years.

b As defined by A Policy on Geometric Design of Highways and Streets, 2004, AASHTO.

6

7

From Table 1,

Section edited to specifically reference number of gyrations for Superpave to come from Table 1 and for Superpave5 to come from Table 2.

8

116 of 141

TS-2d R 35-7 AASHTO

Note 11—For Superpave asphalt mixtures, when specified by the agency and the top of the design layer is ≥100 mm from the pavement surface and the estimated design traffic level is ≥0.3 million ESALs, decrease the estimated design traffic level by one, unless the mixture will be exposed to significant mainline construction traffic prior to being overlaid. If less than 25 percent of a construction lift is within 100 mm of the surface, the lift may be considered to be below 100 mm for mixture design purposes.

Note 12—For Superpave asphalt mixtures, when the estimated design traffic level is between 3 and <10 million ESALs, the Agency may, at its discretion, specify Ninitial at 7, Ndesign at 75, and Nmax at 115.

Table 2—Superpave5 Gyratory Compaction Effort

Design ESALsa

(Million) Compaction Parameters

Typical Roadway Applicationb Ninitial Ndesign Nmax <0.3 5 30 40 Applications include roadways with very light traffic volumes,

such as local roads, county roads, and city streets where truck traffic is prohibited or at a very minimal level. Traffic on these roadways would be considered local in nature, not regional, intrastate, or interstate. Special purpose roadways serving recreational sites or areas may also be applicable to this level.

0.3 to <3 5 30 40 Applications include many collector roads or access streets. Medium-trafficked city streets and the majority of county roadways may be applicable to this level.

3 to <30 6 50 75 Applications include many two-lane, multilane, divided, and partially or completely controlled access roadways. Among these are medium to highly trafficked city streets, many state routes, U.S. highways, and some rural Interstates.

30 6 50 75 Applications include the vast majority of the U.S. Interstate system, both rural and urban in nature. Special applications such as truck-weighing stations or truck-climbing lanes on two-lane roadways may also be applicable to this level.

a The anticipated project traffic level expected on the design lane over a 20-year period. Regardless of the actual design life of the roadway, determine the design ESALs for 20 years.

b As defined by A Policy on Geometric Design of Highways and Streets, 2004, AASHTO.

8.4. Determine the theoretical maximum specific gravity (Gmm) according to T 209 of separate samples representing each of these combinations that have been mixed and conditioned to the same extent as the compacted specimens.

Note 13—The maximum specific gravity for each trial mixture shall be based on the average of at least two tests.

9. EVALUATING COMPACTED TRIAL MIXTURES

9.1. For Superpave or Superpave5 determine the volumetric requirements for the trial mixtures in accordance with M 323.

9.2. Calculate Va and VMA at Ndesign for each trial mixture using Equations 2 and 3:

100 1 mba

mm

GV

G= − (2)

100 mb s

sb

G PVMA

G= − (3)

where:

Gmb = bulk specific gravity of the extruded specimen;

Gmm = theoretical maximum specific gravity of the mixture;

¶

9

When

10

When

¶

The new Table 2 contains mixture design requirements for Superpave5 Rationale: The values in this table represent the results of research done by Professor John Haddock at Purdue University as document in https://docs.lib.purdue.edu/jtrp/1597/ and as implemented by the Indiana DOT https://www.in.gov/dot/div/contracts/standards/book/sep19/400-2020.pdf.

11

Determine

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TS-2d R 35-8 AASHTO

Ps = aggregate content, percent by mass of total mixture; and

Gsb = bulk specific gravity of the combined aggregate.

Note 14—Although the initial trial binder content was estimated for the design air void content (4.0 percent for Superpave and 5.0 for Superpave5), the actual air void content of the compacted specimen is unlikely to match the design exactly. Therefore, the change in binder content needed to obtain the design air void content, and the change in VMA caused by this change in binder content, is estimated. These calculations permit the evaluation of VMA and VFA of each trial aggregate gradation at the design air void content.

9.3. Estimate the volumetric properties at the design percent air voids for each compacted specimen.

9.3.1. Determine the difference in average air void content at Ndesign ( Va) of each aggregate trial blend from the design level using Equation 4 for Superpave or Equation 5 for Superpave5:

4.0a aV VΔ = − (4)

(5)

where:

Va = air void content of the aggregate trial blend at Ndesign gyrations.

9.3.2. Estimate the change in binder content ( Pb) needed to change the air void content to 4.0 percent using Equation 6:

( )0.4b aP VΔ = − Δ (6)

9.3.3. Estimate the change in VMA ( VMA) caused by the change in the air void content ( Va) determined in Section 9.3.1 for each trial aggregate blend gradation, using Equation 7 or 8.

if (7)

(8)

Note 15—A change in binder content affects the VMA through a change in the bulk specific gravity of the compacted specimen (Gmb).

9.3.4. Calculate the VMA for each aggregate trial blend at Ndesign gyrations and design air voids using Equation 9:

design trialVMA VMA VMA= + Δ (9)

where:

VMAdesign = VMA estimated at the design air void content; and VMAtrial = VMA determined at the initial trial binder content.

9.3.5. Using the values of Va determined in Section 9.3.1 and Equation 10, estimate the relative density of each specimen at Ninitial when the design air void content is adjusted to the design air void content at Ndesign:

nitial% 100

i

mb dmm a

mm i

G hG V

G h= − Δ (10)

where:

nitial%

immG = relative density at Ninitial gyrations at the adjusted design binder content;

hd = height of the specimen after Ndesign gyrations, from the Superpave gyratory compactor, mm; and

hi = height of the specimen after Ninitial gyrations, from the Superpave gyratory compactor, mm.

12

a

of

be

4.0 percent

a 4.0 percent

same

, 4.0 percent

4.0

of 4.0 percent

5

5

6 or 7

( )0.2 if 4.0a aVMA V VΔ = Δ >

6

( )0.1 if 4.0a aVMA V VΔ = − Δ <

7

13

4.0 percent

8

8

a

of 4.0 percent

9

4.0 percent

9

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TS-2d R 35-9 AASHTO

9.3.6. Calculate the effective specific gravity of the aggregate (Gse), the estimated percent of effective binder (

estbeP ), and the estimated dust-to-binder ratio (P0.075/Pbe) for each trial blend using

Equations 11, 12, and 13:

100100

bse

b

mm b

PG

P

G G

−=

−

(11)

( )( )

( )est est

se sbbe s b b

se sb

G GP P G P

G G

−= − × +

× (12)

where:

estbeP = estimated effective binder content;

Ps = aggregate content, percent by mass of total mixture;

Gb = specific gravity of the binder;

Gse = effective specific gravity of the combined aggregate;

Gsb = bulk specific gravity of the combined aggregate; and

estbP = estimated binder content at design air voids.

0.0750.075 /

est

bebe

PP P

P= (13)

where:

P0.075 = percent passing the 0.075-mm sieve.

9.3.7. Compare the estimated volumetric properties from each trial aggregate blend gradation at the adjusted design binder content with the criteria specified in M 323. Choose the trial aggregate blend gradation that best satisfies the volumetric criteria.

Note 16—Table 3 presents a Superpave example of the selection of a design aggregate structure from three trial aggregate blend gradations.

Note 17—Many trial aggregate blend gradations will fail the VMA criterion. Generally, the

initial% mmG criterion will be met if the VMA criterion is satisfied. Section 12.1 gives a procedure for

the adjustment of VMA.

Note 18—If the trial aggregate gradations have been chosen to cover the entire range of the gradation controls, then the only remaining solution is to make adjustments to the aggregate production or to introduce aggregates from a new source. The aggregates that fail to meet the required criteria will not produce a quality mix and should not be used. One or more of the aggregate stockpiles should be replaced with another material that produces a stronger structure. For example, a quarry stone can replace a crushed gravel, or crushed fines can replace natural fines.

0

1

2

0

1

4 percent

2

14

2

an

15

16

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TS-2d R 35-10 AASHTO

Table 3—Selection of a Design Aggregate Structure for a Superpave Mixture (Example)

Volumetric Property

Trial Mixture (19.0-mm Nominal Maximum Aggregate) 20-Year Project Design ESALs = 5 million

Criteria

1 2 3

At the Initial Trial Binder Content Pb (trial) 4.4 4.4 4.4

initial% mmG (trial) 88.3 88.0 87.3

design% mmG (trial) 95.6 94.9 94.5

Va at Ndesign 4.4 5.1 5.5 4.0 VMAtrial 13.0 13.6 14.1

Adjustments to Reach Design Binder Content (Va = 4.0% at Ndesign)

Va –0.4 –1.1 –1.5 Pb 0.2 0.4 0.6

VMA –0.1 –0.2 –0.3

At the Estimated Design Binder Content (Va = 4.0 % at Ndesign)

Estimated Pb (design) 4.6 4.8 5.0

VMA (design) 12.9 13.4 13.8 ≥13.0

initial% mmG (design) 88.7 89.1 88.5 ≤89.0

Notes: 1. The top portion of this table presents measured densities and volumetric properties for specimens prepared for each aggregate trial blend at the initial trial binder content.

2. None of the specimens had an air void content of exactly 4.0 percent. Therefore, the procedures described in Section 9 must be applied to (1) estimate the design binder content at which Va = 4.0 percent, and (2) obtain adjusted VMA and relative density values at this estimated binder content.

3. The middle portion of this table presents the change in binder content ( Pb) and VMA ( VMA) that occurs when the air void content (Va) is adjusted to 4.0 percent for each trial aggregate blend gradation.

4. A comparison of the VMA and densities at the estimated design binder content to the criteria in the last column shows that trial aggregate blend gradation No. 1 does not have sufficient VMA (12.9 percent versus a requirement of ≥13.0 percent). Trial blend No. 2 exceeds the criterion for relative density at Ninitial gyrations (89.1 percent versus a requirement of 89.0 percent). Trial blend No. 3 meets the requirement for relative density and VMA and, in this example, is selected as the design aggregate structure.

10. SELECTING THE DESIGN BINDER CONTENT

10.1. Prepare replicate mixtures (Note 8) containing the selected design aggregate structure at each of the following four binder contents: (1) the estimated design binder content, Pb (design); (2) 0.5 percent below Pb (design); (3) 0.5 percent above Pb (design); and (4) 1.0 percent above Pb (design).

10.1.1. Use the number of gyrations previously determined in Section 8.1.

10.2. Condition the mixtures according to R 30, and compact the specimens to Ndesign gyrations according to T 312. Record the specimen height to the nearest 0.1 mm after each revolution.

10.3. Determine the bulk specific gravity (Gmb) of each of the compacted specimens in accordance with T 166 or T 275 as appropriate.

10.4. Determine the theoretical maximum specific gravity (Gmm) according to T 209 of each of the four mixtures using companion samples that have been conditioned to the same extent as the compacted specimens (Note 11).

10.5. Determine the design binder content that produces a target air void content (Va) to meet the design air void at Ndesign gyrations using the following steps:

2

of 4.0 percent

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10.5.1. Calculate Va, VMA, and VFA at Ndesign using Equations 2, 3, and 14:

100 aVMA VVFA

VMA

−= (14)

10.5.2. Calculate the dust-to-binder ratio using Equation 15:

0.0750.075 / be

be

PP P

P= (15)

where:

Pbe = effective binder content.

10.5.3. For each of the four mixtures, determine the average corrected specimen relative densities at Ninitial

( )initial% ,mmG using Equation 16:

initial% 100 mb d

mm

mm i

G hG

G h= (16)

10.5.4. Plot the average Va, VMA, VFA, and relative density at Ndesign for replicate specimens versus binder content.

Note 19—All plots are generated automatically by the Superpave software. Figure 2 presents a sample data set and the associated plots.

10.5.5. By graphical or mathematical interpolation (Figure 2), determine the binder content to the nearest 0.1 percent at which the target Va is equal to the design requirement. This is the design binder content (Pb) at Ndesign.

10.5.6. By interpolation (Figure 2), verify that the volumetric requirements specified in M 323 are met at the design binder content.

10.6. Compare the calculated percent of maximum relative density with the design criteria at Ninitial by interpolation, if necessary. This interpolation can be accomplished by the following procedure.

10.6.1. Prepare a densification curve for each mixture by plotting the measured relative density at X gyrations, %

XmmG , versus the logarithm of the number of gyrations (see Figure 3).

10.6.2. Examine a plot of air void content versus binder content. Determine the difference in air voids between the design air void content and the air void content at the nearest, lower binder content. Determine the air void content at the nearest, lower binder content at its data point, not on the line of best fit. Designate the difference in air void content as Va.

10.6.3. Using Equation 16, determine the average corrected specimen relative densities at Ninitial

( )initial% mmG Confirm that initial

% mmG satisfies the design requirements in M 323 at the design

binder content.

3

3

4

4

5

5

17

4.0 percent

4.0 percent

5

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Average Va, VMA, VFA, and Relative Density at Ndesign

Pb (%) Va (%) VMA (%) VFA (%) Density at Ndesign

(kg/m3) 4.3 9.5 15.9 40.3 2320

4.8 7.0 14.7 52.4 2366 5.3 6.0 14.9 59.5 2372

5.8 3.7 13.9 73.5 2412

Notes: 1. In this example, the estimated design binder content is 4.8 percent; the minimum VMA requirement for the design aggregate structure (19.0-mm nominal maximum size) is 13.0 percent, and the VFA requirement is 65 to 75 percent.

2. Entering the plot of percent air voids versus percent binder content at 4.0 percent air voids, the design binder content is determined as 5.7 percent.

3. Entering the plots of percent VMA versus percent binder content and percent VFA versus percent binder content at 5.7 percent binder content, the mix meets the VMA and VFA requirements.

Figure 2—Sample Volumetric Design Data for a Superpave Mixture at Ndesign

4.0 5.0 6.04.5 5.5 6.5Percent Binder Content

12

13

14

15

16

17

Pe

rce

nt V

MA


2250

2300

2350

2400

2450

Den

sity

, kg/

m3

5.0 6.04.5 5.5 6.5Percent Binder Content


10

20

30

40

50

60

Pe

rce

nt V

FA

70

80

90

2

4

6

8

10

12

Per

cen

tAir

Voi

ds

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Figure 3—Sample Densification Curve

10.7. Prepare replicate (Note 8) specimens composed of the design aggregate structure at the design

binder content to confirm that max% mmG

satisfies the design requirements in M 323.

10.7.1. Condition the mixtures according to R 30, and compact the specimens according to T 312 to the maximum number of gyrations, Nmax, from Table 1 for Superpave or from Table 2 for Superpave5.

10.7.2. Determine the average specimen relative density at Nmax, max% mmG

, by using Equation 17, and

confirm that max% mmG

satisfies the volumetric requirement in M 323.

max% 100 mb

mm

mm

GG

G=

(16)

where:

max% mmG

= relative density at Nmax gyrations at the design binder content.

11. EVALUATING MOISTURE SUSCEPTIBILITY

11.1. Prepare six mixture specimens (nine are needed if freeze–thaw testing is required) composed of the design aggregate structure at the design binder content. Oven-condition the mixture according to T 283 Section 6, and compact the specimens to 7.0 ± 0.5 percent air voids for Superpave mixtures or to 5.0 ± 0.5 percent air voids for Superpave5 mixtures according to T 312.

11.2. Group, moisture-condition, test, and evaluate specimens according to T 283. Ensure the asphalt mixture used to determine theoretical maximum specific gravity (Gmm) is cured, heated or dried according to T 283, Section 9.1 during the evaluation and grouping of specimens. After curing, heating, or drying according to T 283, Section 9.1, do not further condition the asphalt mixture according to T 209, Section 9.2 before placing the asphalt mixture in a flask, bowl or pycnometer to determine the theoretical maximum specific gravity (Gmm). The design shall meet the tensile strength ratio requirement of M 323.

1 10 100

75.0

77.0

79.0

81.0

83.0

85.0

87.0

89.0

91.0

93.0

96.0

97.0

99.0

Number of Gyrations

% M

ax T

heo. D

ensity

6

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11.3. If the tensile strength ratio is less than 0.80, as required in M 323, remedial action such as the use of antistrip agents is required to improve the moisture susceptibility of the mix. When remedial agents are used to modify the binder, retest the mix to assure compliance with the 0.80 minimum requirement.

Note 20—The specifying agency may require Hamburg wheel-track testing according to T 324 for evaluating moisture susceptibility.

12. ADJUSTING THE MIXTURE TO MEET PROPERTIES

12.1. Adjusting VMA—If a change in the design aggregate skeleton is required to meet the specified VMA, there are three likely options: (1) change the gradation (Note 18); (2) reduce the minus 0.075-mm fraction (Note 19); or (3) change the surface texture and/or shape of one or more of the aggregate fractions (Note 20).

Note 21—Changing gradation may not be an option if the trial aggregate blend gradation analysis includes the full spectrum of the gradation control area.

Note 22—Reducing the percent passing the 0.075-mm sieve of the mix will typically increase the VMA. If the percent passing the 0.075-mm sieve is already low, this is not a viable option.

Note 23—This option will require further processing of existing materials or a change in aggregate sources.

12.2. Adjusting VFA—The lower limit of the VFA range should always be met at the design air voids if the VMA meets the requirements. If the upper limit of the VFA is exceeded, then the VMA is substantially above the minimum required. If so, redesign the mixture to reduce the VMA. Actions to consider for redesign include: (1) changing to a gradation that is closer to the maximum density line; (2) increasing the minus 0.075-mm fraction, if room is available within the specification control points; or (3) changing the surface texture and shape of the aggregates by incorporating material with better packing characteristics, e.g., less thin, elongated aggregate particles.

12.3. Adjusting the Tensile Strength Ratio—The tensile strength ratio can be increased by (1) adding chemical antistrip agents to the binder to promote adhesion in the presence of water; or (2) adding hydrated lime to the mix.

13. REPORT

13.1. The report shall include the identification of the project number, traffic level, and mix design number.

13.2. The report shall include information on the design aggregate structure including the source of aggregate, kind of aggregate, required quality characteristics, and gradation.

13.3. The report shall contain information about the design binder including the source of binder and the performance grade.

13.4. The report shall contain information about the HMA including the percent of binder in the mix; the relative density; the number of initial, design, and maximum gyrations; and the VMA, VFA, Vbe, Vba, Va, and dust-to-binder ratio.

14. KEYWORDS

14.1. Asphalt mix design; Superpave; volumetric mix design.

18

19

20

21

4.0 percent

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APPENDIXES


X1. CALCULATING AN INITIAL TRIAL BINDER CONTENT FOR EACH AGGREGATE TRIAL BLEND

X1.1. Calculate the bulk and apparent specific gravities of the combined aggregate in each trial blend using the specific gravity data for the aggregate fractions obtained in Section 6.6 and Equations X1.1 and X1.2:

1 2

1 2

1 2

nsb

n

n

P P PG

PP P

G G G

+ + +=

+ + +

(X1.1)

1 2

1 2

1 2

nsa

n

n

P P PG

PP P

G G G

+ + +=

+ + +

(X1.2)

where:

Gsb = bulk specific gravity for the combined aggregate; P1, P2, . . .Pn = percentages by mass of aggregates 1, 2, . . .n; G1, G2, . . .Gn = bulk specific gravities (Equation X1.1) or apparent specific gravities

(Equation X1.2) of aggregates 1, 2, n; and Gsa = apparent specific gravity for the combined aggregate.

X1.2. Estimate the effective specific gravity of the combined aggregate in the aggregate trial blend using Equation X1.3:

Gse = Gsb + 0.8(Gsa – Gsb) (X1.3)

where:

Gse = effective specific gravity of the combined aggregate;

Gsb = bulk specific gravity of the combined aggregate; and

Gsa = apparent specific gravity of the combined aggregate.

Note X1—The multiplier, 0.8, can be changed at the discretion of the designer. Absorptive aggregates may require values closer to 0.6 or 0.5.

Note X2—The Superpave mix design system includes a mixture-conditioning step before the compaction of all specimens; this conditioning generally permits binder absorption to proceed to completion. Therefore, the effective specific gravity of Superpave mixtures will tend to be close to the apparent specific gravity in contrast to other design methods where the effective specific gravity generally will lie near the midpoint between the bulk and apparent specific gravities.

X1.3. Estimate the volume of binder absorbed into the aggregate, Vba, using Equations X1.4 and X1.5:

1 1ba s

sb se

V WG G

= − (X1.4)

where:

Ws, the mass of aggregate in 1 cm3 of mix, g, is calculated as:

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( )1s as

b s

b se

P VW

P P

G G

−=

+

(X1.5)

and where:

Ps = mass percent of aggregate, in decimal equivalent, assumed to be 0.95;

Va = volume of air voids, assumed to be 0.04 cm3 in 1 cm3 of mix for Superpave and 0.05 cm3 for Superpave5;

Pb = mass percent of binder, in decimal equivalent, assumed to be 0.05; and

Gb = specific gravity of the binder.

Note X3—This estimate calculates the volume of binder absorbed into the aggregate, Vba, and subsequently the initial, trial binder content at a target air void content of 4.0 percent.

X1.4. Estimate the volume of effective binder using Equation X1.6:

( )0.176 0.0675logbe nV S= − (X1.6)

where:

Vbe = volume of effective binder, cm3; and

Sn = nominal maximum sieve size of the largest aggregate in the aggregate trial blend, mm.

Note X4—This regression equation is derived from an empirical relationship between (1) VMA and Vbe when the air void content, Va, is equal to 4.0 percent: Vbe = VMA – Va = VMA – 4.0 for Superpave or 5.0 percent: Vbe = VMA – Va = VMA – 5.0 for Superpave5 and (2) the relationship between VMA for Superpave and Superpave5, respectively, and the nominal maximum sieve size of the aggregate in M 323.

X1.5. Calculate the estimated initial trial binder (Pbi) content for the aggregate trial blend gradation using Equation X1.7:

( )

( )( )100 b be ba

bi

b be ba s

G V VP

G V V W

+=

+ + (X1.7)

where:

Pbi = estimated initial trial binder content, percent by weight of total mix.

X2. SPECIAL MIXTURE DESIGN CONSIDERATIONS AND PRACTICES FOR WARM MIX ASPHALT (WMA)

X2.1. Purpose:

X2.1.1. This appendix presents special mixture design considerations and methods for designing warm mix asphalt (WMA) using R 35. WMA refers to asphalt mixtures that are produced at temperatures approximately 50°F (28°C) or more lower than typically used in the production of HMA (hot mix asphalt). The goal of WMA is to produce mixtures with equivalent strength, durability, and performance characteristics as HMA using substantially reduced production temperatures. These special mixture design considerations and practices are applicable anytime a WMA technology is being used. The WMA technologies may be used as coating and compaction aids without lowering the production temperature by 50°F (28°C).

X2.1.2. The practices in this appendix are applicable to a wide range of WMA technologies including: WMA additives that are added to the asphalt binder,

WMA additives that are added to the mixture during production,

Note, this equation applies for both Superpave and Superpave5 of the same nominal maximum size because the minimum Vbe is the same for either mixture.

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Wet aggregate mixtures, and

Plant foaming processes.

X2.1.3. The information in this appendix supplements the procedures in R 35 and applies to both Superpave and Superpave5 mixtures. This appendix assumes the user is proficient with the standard procedures in R 35.

X2.2. Summary:

X2.2.1. This appendix includes separate sections addressing the following aspects of WMA mixture design:

Additional Laboratory Equipment;

WMA Technology Selection;

Binder Grade Selection;

RAP in WMA;

Technology-Specific Specimen Fabrication Procedures; WMA Mixture Evaluations:

• Coating, • Compactability, • Evaluating of Moisture Sensitivity, • Evaluation of Rutting Resistance; and

Adjusting the Mixture to Meet Specification Requirements.

X2.2.2. In each section, reference is made to the applicable section of R 35.

X2.3. Additional Laboratory Equipment:

X2.3.1. All WMA Processes:

X2.3.1.1. Mechanical Mixer—A planetary mixer with a wire whip having a capacity of 20-qt or a 5-gal bucket mixer.

Note X5—The mixing times in this appendix were developed using a planetary mixer with a wire whip, Blakeslee Model B-20 or equivalent. Appropriate mixing times for bucket mixers should be established by evaluating the coating of asphalt mixtures prepared at the viscosity-based mixing temperatures specified in T 312.

X2.3.2. Binder Additive WMA Processes:

X2.3.2.1. Low-Shear Mechanical Stirrer—A low-shear mechanical stirrer with appropriate impeller to homogeneously blend the additive in the binder.

X2.3.3. Plant Foaming Processes:

X2.3.3.1. Laboratory Foamed Asphalt Plant—A laboratory-scale foamed asphalt plant capable of producing consistent foamed asphalt at the water content used in field production. The device should be capable of producing foamed asphalt for laboratory batches ranging from approximately 10 to 20 kg.

X2.4. WMA Technology Selection:

X2.4.1. There are more than 20 WMA technologies being marketed in the United States. Select the WMA technology that will be used in consultation with the specifying agency and technical representatives from the WMA technology providers. Consideration should be given to a number

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of factors including (1) available performance data, (2) the cost of the WMA additives, (3) planned production and compaction temperatures, (4) planned production rates, (5) plant capabilities, and (6) modifications required to successfully use the WMA technology with available field and laboratory equipment.

X2.4.2. Determine the planned production and field compaction temperatures.

X2.5. Binder Grade Selection:

X2.5.1. Use the same grade of binder normally used with HMA. Select the performance grade of the binder in accordance with M 323, considering the environment and traffic at the project site.

Note X6—For WMA technologies having production temperatures that are 100°F (56°C) or more lower than HMA production temperatures, it may be necessary to increase the high-temperature performance grade of the binder one grade level to meet the rutting resistance requirements included in this appendix.

X2.6. RAP in WMA:

X2.6.1. For WMA mixtures incorporating RAP, the planned field compaction temperature shall be greater than the as-recovered high-temperature grade of the RAP binder.

Note X7—This requirement is included to ensure mixing of the new and reclaimed binders. Laboratory studies showed that new and reclaimed binders do mix at WMA process temperatures provided this requirement is satisfied and the mixture remains at or above the planned compaction temperature for at least 2 h. Plant mixing should be verified through an evaluation of volumetric or stiffness properties of plant-produced mixtures.

X2.6.2. Select RAP materials in accordance with M 323.

X2.6.3. For blending chart analyses, the intermediate and low-temperature properties of the virgin binder may be improved using Table X2.1. Note X8—The intermediate and low-temperature grade improvements given in Table X2.1 will allow additional RAP to be used in WMA mixtures when blending chart analyses are used. An approximate 0.6°C improvement in the low-temperature properties will allow approximately 10 percent additional RAP binder to be added to the mixture based on blended binder grade requirements.

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Table X2.1—Recommended Improvement in Virgin Binder Low-Temperature Continuous Grade for RAP Blending Chart Analysis for WMA Production Temperatures

Virgin binder PG grade 58-28 58-22 64-22 64-16 67-22

Average HMA production temperature, °F

285 285 292 292 300

Rate of improvement of virgin binder low-temperature grade per 1°C reduction in plant temperature

0.035 0.025 0.025 0.012 0.025

WMA Production Temperature, °F Recommended Improvement in Virgin Binder Low-Temperature

Continuous Grade for RAP Blending Chart Analysis, °C

300 NA NA NA NA 0.0

295 NA NA NA NA 0.1

290 NA NA 0.0 0.0 0.1

285 0.0 0.0 0.1 0.0 0.2

280 0.1 0.1 0.2 0.1 0.3 275 0.2 0.1 0.2 0.1 0.3

270 0.3 0.2 0.3 0.1 0.4

265 0.4 0.3 0.4 0.2 0.5

260 0.5 0.3 0.4 0.2 0.6

255 0.6 0.4 0.5 0.2 0.6

250 0.7 0.5 0.6 0.3 0.7 245 0.8 0.6 0.7 0.3 0.8

240 0.9 0.6 0.7 0.3 0.8

235 1.0 0.7 0.8 0.4 0.9

230 1.1 0.8 0.9 0.4 1.0

225 1.2 0.8 0.9 0.4 1.0

220 1.3 0.9 1.0 0.5 1.1 215 1.4 1.0 1.1 0.5 1.2

210 1.5 1.0 1.1 0.5 1.3

X2.6.4. Blending Chart Example:

X2.6.4.1. Problem Statement—A producer will be producing WMA using a virgin PG 64-22 binder at a temperature of 250°F. In the mixture, 35 percent of the total binder will be replaced with RAP binder, so according to M 323 a blending chart analysis is needed. The continuous grade of the recovered RAP binder is PG 93.0 (29.4) – 18.1. The continuous grade of the virgin PG 64-22 binder is PG 66.2 (21.1) – 23.9. The specified grade for the blended binder in the mixture is PG 64-22. Use the M 323 blending chart analysis to determine if the proposed RAP and virgin binder provide an acceptable blended binder.

X2.6.4.2. Solution as WMA—Because the mixture will be produced as WMA at 250°F, determine the virgin binder grade improvement for the blending chart analysis by entering Table X2.1 in the PG 64-22 column and reading the intermediate- and low-temperature improvement from the row for 250°F. The intermediate- and low-temperature grade improvement is 0.6°C. For WMA at 250°F, perform the M 323 blending chart analysis using PG 66.2 (20.5) –24.5 for the virgin binder and PG 93.0 (29.4) –18.1 for the RAP Binder. Because a PG 64-XX virgin binder is being used and a PG 64-XX is specified, it is not necessary to check the high-temperature grade. Use Equation X1.12 from M 323 to determine the maximum allowable RAP content based on the intermediate and low temperatures. For PG 64-22, 25°C is the maximum allowable blended binder intermediate-temperature grade and –22°C the maximum allowable blended binder low-temperature grade.

( )

( )

blend virgin

RAP virgin

%RAP 100T T

T T

−= ×

− (Eq. X1.12 from M 323)

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where:

Tblend = continuous grade temperature of the blended binder (high, intermediate, low);

Tvirgin = continuous grade temperature of the virgin binder (high, intermediate, low); and

TRAP = continuous grade temperature of the RAP binder (high, intermediate, low).

Maximum RAP Binder Based on Intermediate-Temperature Grade:

( )

( )

25 20.5 4.5%RAP 100 100 50.5%

29.4 20.5 8.9

−= × = × =

−

Maximum RAP Binder Based on Low-Temperature Grade:

( )( )

( )( )

22 24.5 2.5%RAP 100 100 39.0%

6.418.1 24.5

− − −= × = × =

− −

The critical property is the low-temperature grade, which allows 39.0 percent of the binder to be RAP binder. The proposed mixture contains only 35 percent RAP binder; therefore, it is acceptable.

X2.6.4.3. Solution as HMA—If the mixture were produced as HMA, the blending chart analysis would be completed using PG 66.2 (21.1) –23.9 for the virgin binder and PG 93.0 (29.4) –18.1 for the RAP binder.

Maximum RAP Binder Based on Intermediate-Temperature Grade:

( )

( )

25 21.1 3.9%RAP 100 100 47.0%

29.4 21.1 8.3

−= × = × =

−

Maximum RAP Binder Based on Low-Temperature Grade:

( )( )

( )( )

22 23.9 1.9%RAP 100 100 32.7%

5.818.1 23.9

− − −= × = × =

− −

Again the critical property is the low-temperature grade, but this time the proposed RAP binder content of 35 percent exceeds the maximum allowable of 32.7 percent; therefore, the HMA mixture is not acceptable.

X2.7. Technology-Specific Specimen Fabrication Procedures:

X2.7.1. Batching:

X2.7.1.1. Determine the number and size of specimens that are required. Table X2.2 summarizes approximate specimen sizes for WMA mixture design.

Note X9—The mass of mixture required for the various specimens depends on the specific gravity of the aggregate and the air void content of the specimen. Trial specimens may be required to determine appropriate batch weights for T 283 and flow number testing.

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Table X2.2—Specimen Requirements

Specimen Type Gyratory

Specimen Size Approximate

Specimen Mass Number Required Maximum specific gravity

NA 500 to 6000 g depending on maximum aggregate size

2 per trial blend, plus 8 to determine design binder content, plus 1 at the design binder content for compactability evaluation

Volumetric design 150-mm diameter by 115 mm high

4700 g 2 per trial blend, plus 8 to determine design binder content

Coating NA 500 to 6,000 g depending on maximum aggregate size

1 at the design binder content

Compactability 150-mm diameter by 115 mm high

4700 g 4 at the design binder content

T 283 150-mm diameter by 95 mm high


Flow number 150-mm diameter by 175 mm high


X2.7.1.2. Prepare a batch sheet showing the batch weight of each aggregate fraction, RAP, and the asphalt binder.

X2.7.1.3. Weigh into a pan the weight of each aggregate fraction.

Note X10—For WMA processes that use wet aggregate, weigh the portion of the aggregate that will be heated into one pan and weigh the portion of the aggregate that will be wetted into a second pan.

X2.7.1.4. Weigh into a separate pan, the weight of RAP.

X2.7.2. Heating:

X2.7.2.1. Place the aggregate in an oven set at approximately 15°C higher than the planned production temperature.

Note X11—The aggregate will require 2 to 4 h to reach the temperature of the oven. Aggregates may be placed in the oven overnight.

X2.7.2.2. Heat the RAP in the oven with the aggregates, but limit the heating time for the RAP to 2 h.

X2.7.2.3. Heat the binder to the planned production temperature.

X2.7.2.4. Heat mixing bowls and other tools to the planned production temperature.

X2.7.2.5. Preheat a forced draft oven and pans to the planned field compaction temperature for use in short-term conditioning the mixture.

X2.7.3. Preparation of WMA Mixtures with WMA Additive Added to the Binder:

Note X12—If specific mixing and storage instructions are provided by the WMA additive supplier, follow the supplier’s instructions.

X2.7.3.1. Adding WMA Additive to Binder:

X2.7.3.1.1. Weigh the required amount of the additive into a small container.

Note X13—The additive is typically specified as a percent by weight of binder. For mixtures containing RAP, determine the weight of additive based on the total binder content of the mixture.

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X2.7.3.1.2. Heat the asphalt binder in a covered container in an oven set at 135°C until the binder is sufficiently fluid to pour. During heating occasionally stir the binder manually to ensure homogeneity.

X2.7.3.1.3. Add the required amount of additive to the binder, and stir it with a mechanical stirrer until the additive is totally dispersed in the binder.

X2.7.3.1.4. Store the binder with WMA additive at room temperature in a covered container until needed for use in the mixture design.

X2.7.3.2. Preparing WMA Specimens:

X2.7.3.2.1. Heat the mixing tools, aggregate, RAP, and binder in accordance with Section X2.7.2.

X2.7.3.2.2. If a liquid antistripping additive is required, add it to the binder per the manufacturer’s instructions.

X2.7.3.2.3. Place the hot mixing bowl on a scale, and tare the scale.

X2.7.3.2.4. Charge the mixing bowl with the heated aggregates and RAP, and dry-mix thoroughly.

X2.7.3.2.5. Form a crater in the blended aggregate, and weigh the required amount of asphalt binder into the mixture to achieve the desired batch weight.

Note X14—If the aggregates and RAP have been stored for an extended period of time in a humid environment, then it may be necessary to adjust the weight of binder based on the oven-dry weight of the aggregates and RAP as follows:

1. Record the oven-dry weight of the aggregates and RAP, wi.

2. Determine the target total weight of the mixture as follows:

new1100

it

b

ww

P=

−

(X2.1)

where:

wt = target total weight, g;

wi = oven-dry weight from Step 1, g; and

newbP = percent by weight of total mix of new binder in the mixture.

3. Add new binder to the bowl to reach wt.

X2.7.3.2.6. Remove the mixing bowl from the scale, and mix the material with a mechanical mixer for 90 s.

X2.7.3.2.7. Oven-condition the mixture by placing it in a flat, shallow pan at an even thickness of 25 to 50 mm, and place the pan in the forced-draft oven for 2 h ± 5 min at the planned field compaction temperature ± 3°C. Stir the mixture once after 1 h ± 5 min to maintain uniform conditioning.

X2.7.4. Preparation of WMA Mixtures with WMA Additive Added to the Mixture:

Note X15—If specific mixing and storage instructions are provided by the WMA additive supplier, follow the supplier’s instructions.

X2.7.4.1. Weigh the required amount of the additive into a small container.

Note X16—The quantity of additive may be specified as a percent by weight of binder or a percent by weight of total mixture.

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X2.7.4.2. If a liquid antistripping additive is required, add it to the binder per the manufacturer’s instructions.

X2.7.4.3. Heat the mixing tools, aggregate, RAP, and binder in accordance with Section X2.7.2.

X2.7.4.4. Place the hot mixing bowl on a scale, and tare the scale.

X2.7.4.5. Charge the mixing bowl with the heated aggregates and RAP, and dry-mix thoroughly.

X2.7.4.6. Form a crater in the blended aggregate, and weigh the required amount of asphalt binder into the mixture to achieve the desired batch weight.


1. Record the oven-dry weight of the aggregates, and RAP, wi.


new1100

it

b

ww

P=

−

(X2.2)

where:




3. Add new binder to the bowl to reach wt.

X2.7.4.7. Pour the WMA additive into the pool of new asphalt binder.

X2.7.4.8. Remove the mixing bowl from the scale, and mix material with a mechanical mixer for 90 s.

X2.7.4.9. Oven-condition the mixture by placing it in a flat, shallow pan at an even thickness of 25 to 50 mm, and place the pan in the forced-draft oven for 2 h ± 5 min at the planned field compaction temperature ± 3°C. Stir the mixture once after 1 h ± 5 min to maintain uniform conditioning.

X2.7.5. Preparation of WMA Mixtures with a Wet Fraction of Aggregate:

Note X18—Consult the WMA process supplier for appropriate additive dosage rates, mixing temperatures, percentage of wet aggregate, and wet aggregate moisture content.

X2.7.5.1. Adding WMA Additive to Binder:

X2.7.5.1.1. Weigh the required amount of the additive into a small container.

Note X19—The additive is typically specified as a percent by weight of binder. For mixtures containing RAP, determine the weight of additive based on the total binder content of the mixture.

X2.7.5.1.2. Heat the asphalt binder in a covered container in an oven set at 135°C until the binder is sufficiently fluid to pour. During heating occasionally stir the binder manually to ensure homogeneity.

X2.7.5.1.3. Add the required amount of additive to the binder, and stir it with a mechanical stirrer until the additive is totally dispersed in the binder.

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X2.7.5.2. Preparing WMA Specimens:

X2.7.5.2.1. Add the required amount of moisture to the wet fraction of the aggregate. Mix it thoroughly, then cover and let stand for at least 2 h before mixing it with the heated fraction.

X2.7.5.2.2. Heat the mixing tools, dry aggregate portion, and dry RAP portion to the initial mixing temperature in accordance with Section X2.7.2.

X2.7.5.2.3. Place the hot mixing bowl on a scale, and tare the scale.

X2.7.5.2.4. Charge the mixing bowl with the heated aggregates and RAP, and dry-mix thoroughly.

X2.7.5.2.5. Form a crater in the blended aggregate, and weigh the required amount of asphalt binder into the mixture to achieve the desired batch weight.

Note X20—If the aggregates and RAP have been stored for an extended period of time in a humid environment, it may be necessary to adjust the weight of binder based on the oven-dry weight of the aggregates and RAP as follows:



( )

new1100

i dwf

tb

w ww

P

+=

−

(X2.3)

where:


wi = oven-dry weight from Step 1, g;

wdwf = oven-dry weight of the wet fraction from the batch sheet, g; and


3. Determine the target weight of the heated mixture:

thm t dwfw w w= − (X2.4)

where:

wthm = target weight of the heated mixture, g;

wt = target total weight, g; and

wdwf = oven-dry weight of the wet fraction from the batch sheet.

4. Add new binder to the bowl to reach wthm.

X2.7.5.2.6. Add the additive to the binder immediately before mixing it with the heated fraction of the aggregate according to Section X2.7.5.1.

X2.7.5.2.7. Remove the mixing bowl from the scale, and mix the material with a mechanical mixer for 30 s.

X2.7.5.2.8. Stop the mixer, and immediately add the wet fraction aggregate.

X2.7.5.2.9. Restart the mixer, and continue to mix for 60 s.

X2.7.5.2.10. Place the mixture in a flat, shallow pan at an even thickness of 25 to 50 mm.

X2.7.5.2.11. Check the temperature of the mixture in the pan to ensure it is between 90 and 100°C.

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X2.7.5.2.12. Oven-condition the mixture by placing the pan in the forced-draft oven for 2 h ± 5 min at the planned field compaction temperature ± 3°C. Stir the mixture once after 1 h ± 5 min to maintain uniform conditioning.

X2.7.6. Preparation of Foamed Asphalt Mixtures:

X2.7.6.1. The preparation of foamed asphalt mixtures requires special asphalt binder foaming equipment that can produce foamed asphalt using the amount of moisture that will be used in field production.

X2.7.6.2. Prepare the asphalt binder foaming equipment, and load it with binder per the manufacturer’s instructions.

X2.7.6.3. If a liquid antistripping additive is required, add it to the binder in the foaming equipment according to the manufacturer’s instructions.

X2.7.6.4. Heat the mixing tools, aggregate, and RAP in accordance with Section X2.7.2.

X2.7.6.5. Prepare the foamed asphalt binder according to the instructions for the foaming equipment.

X2.7.6.6. Place the hot mixing bowl on a scale, and tare the scale.

X2.7.6.7. Charge the mixing bowl with the heated aggregates and RAP, and dry-mix thoroughly.

X2.7.6.8. Form a crater in the blended aggregate, and add the required amount of foamed asphalt into the mixture to achieve the desired batch weight.

Note X21—The laboratory foaming equipment uses a timer to control the amount of foamed asphalt produced. Ensure the batch size is large enough that the required amount of foamed asphalt is within the calibrated range of the foaming device. This operation may require producing one batch for the two gyratory specimens and the two maximum specific gravity specimens at each asphalt content, then splitting the larger batch into individual samples.




new1100

it

b

ww

P=

−

(X2.5)

where:




3. Add foamed binder to the bowl to reach wt.

X2.7.6.9. Remove the mixing bowl from the scale, and mix the materials with a mechanical mixer for 90 s.

X2.7.6.10. Oven-condition the mixture by placing it in a flat, shallow pan at an even thickness of 25 to 50 mm, and place the pan in the forced-draft oven for 2 h ± 5 min at the planned field compaction temperature ± 3°C. Stir the mixture once after 1 h ± 5 min to maintain uniform conditioning.

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X2.8. WMA Mixture Evaluations:

X2.8.1. At the optimum binder content determined in accordance with R 35, prepare WMA mixtures in accordance with the appropriate procedure from Section X2.7 for the following evaluations:

Coating

Compactability

Moisture sensitivity

Rutting resistance

X2.8.2. Coating:

X2.8.2.1. Prepare a sufficient amount of mixture at the design binder content to perform the coating evaluation procedure in T 195 using the appropriate WMA fabrication procedure from Section X2.7. Do not oven-condition the mixture.

X2.8.2.2. Evaluate the coating in accordance with T 195.

X2.8.2.3. The recommended coating criterion is at least 95 percent of the coarse aggregate particles being fully coated.

X2.8.3. Compactability:

X2.8.3.1. Prepare a sufficient amount of mixture at the design binder content for four gyratory specimens and one maximum specific gravity measurement using the appropriate WMA fabrication procedure from Section X2.7 including oven-conditioning for 2 h ± 5 min at the planned field compaction temperature.

X2.8.3.2. Determine the theoretical maximum specific gravity (Gmm) according to T 209.

X2.8.3.3. Compact duplicate specimens at the planned field compaction temperature to Ndesign gyrations according to T 312. Record the specimen height for each gyration.

X2.8.3.4. Determine the bulk specific gravity (Gmb) of each specimen according to T 166.

X2.8.3.5. Allow the mixture to cool to 30°C below the planned field compaction temperature. Compact duplicate specimens according to T 312 to Ndesign gyrations determined from Table 1 for Superpave or from Table 2 for Superpave5. Record the specimen height for each gyration.

X2.8.3.6. Determine the bulk specific gravity (Gmb) of each specimen according to T 166.

X2.8.3.7. For each specimen, determine the corrected specimen relative densities for each gyration using Equation X2.6:

% 100N

mb dmm

mm N

G hG

G h= (X2.6)

where:

%NmmG = relative density at N gyrations;

Gmb = bulk specific gravity of the specimen compacted to Ndesign gyrations;

hd = height of the specimen after Ndesign gyrations, from the Superpave gyratory compactor, mm; and

hN = height of the specimen after N gyrations, from the Superpave gyratory compactor, mm.

according to T 312

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X2.8.3.8. For each Superpave specimen, determine the number of gyrations needed to reach 92 percent relative density. For each Superpave5 specimen, determine the number of gyrations needed to reach 95 percent relative density.

X2.8.3.9. For Superpave mixtures determine the average number of gyrations needed to reach 92 percent relative density at the planned field compaction temperature. For Superpave5 mixtures determine the average number of gyrations needed to reach 95 percent relative density at the planned field compaction temperature.

X2.8.3.10. For Superpave mixtures determine the average number of gyrations needed to reach 92 percent relative density at 30°C below the planned field compaction temperature. For Superpave5 mixtures determine the average number of gyrations needed to reach 95 percent relative density at 30°C below the planned field compaction temperature.

X2.8.3.11. Determine the gyration ratio using Equation X2.7 for Superpave or X2.8 for Superpave5:

( )

( )

92 30

92

ratio T

T

N

N−

= (X2.7)

where:

ratio = gyration ratio;

(N92)T – 30 = gyrations needed to reach 92 percent relative density at 30°C below the planned field compaction temperature; and

(N92)T = gyrations needed to reach 92 percent relative density at the planned field compaction temperature.

ratio (X2.8)

where:

ratio = gyration ratio;

(N92)T – 30 = gyrations needed to reach 95 percent relative density at 30°C below the planned field compaction temperature; and

(N92)T = gyrations needed to reach 95 percent relative density at the planned field compaction temperature.

X2.8.3.12. The recommended compactability criterion is a gyration ratio less than or equal to 1.25.

Note X23—The compactability criterion limits the temperature sensitivity of WMA to that for a typical HMA mixture. The criterion is based on limited research conducted in NCHRP 9-43. The criterion should be considered tentative and subject to change as additional data on WMA mixtures are collected.

X2.8.4. Evaluating Moisture Sensitivity:

X2.8.4.1. Prepare a sufficient amount of mixture at the design binder content for six gyratory specimens using the appropriate WMA fabrication procedure from Section X2.7 without oven-conditioning required by Section X2.7.3.2.7, Section X2.7.4.9, Section X2.7.5.2.12, or Section X2.7.6.10. Oven-condition the mixture according to T 283, Section 6.

X2.8.4.2. For Superpave compact test specimens to 7.0 ± 0.5 percent air voids according to T 312. For Superpave5 compact test specimens to 5.0 ± 0.5 percent air voids according to T 312.

X2.8.4.3. Group, moisture-condition, test, and evaluate the specimens according to T 283.

D

D

C

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X2.8.4.4. The recommended moisture sensitivity criteria are a tensile strength ratio greater than 0.80 and no visual evidence of stripping.

X2.8.5. Evaluating Rutting Resistance:

X2.8.5.1. Evaluate rutting using the flow number test in T 378.

Note X24—WMA additives and processes may affect the rutting resistance of the mixture and rutting resistance should be evaluated. Agencies with established criteria for other test methods, such as T 320 (SST), T 324 (Hamburg), and T 340 (APA), may specify those methods in lieu of T 378.

X2.8.5.2. Prepare a sufficient amount of mixture at the design binder content for four flow number test specimens using the appropriate WMA fabrication procedure from Section X2.7 including oven-conditioning for 2 h ± 5 min at the planned field compaction temperature.

X2.8.5.3. The test is conducted on 100-mm diameter by 150-mm-high test specimens that are sawed and cored from larger gyratory specimens that are 150-mm diameter by at least 160 mm high. Refer to R 83 for detailed test specimen fabrication procedures. Do not oven-condition the mixture according to R 83, Section 9.2.3. Oven-condition WMA mixtures according to Section X2.7.

X2.8.5.4. For Superpave mixtures prepare the flow number test specimens to 7.0 ± 1.0 percent air voids. For Superpave5 mixtures prepare the flow number test specimens to 5.0 ± 1.0 percent air voids.

X2.8.5.5. Perform the flow number test at the design temperature at 50 percent reliability as determined using LTPPBind Version 3.1. The temperature is computed at 20 mm for surface courses, and the top of the pavement layer for intermediate and base courses.

X2.8.5.6. Perform the flow number test unconfined using a repeated deviatoric stress of 600 kPa with a contact deviatoric stress of 30 kPa.

X2.8.5.7. Determine the flow number for each specimen; then average the results. Compare the average flow number with the criteria given in Table X2.3.

Table X2.3—Minimum Flow Number Requirements

Traffic Level, Million ESALs Minimum Flow Number <3 NA

3 to <10 30

10 to <30 105

≥30 415

X2.9. Adjusting the Mixture to Meet Specification Properties:

X2.9.1. This section provides guidance for adjusting the mixture to meet the evaluation criteria contained in Section X2.8. For WMA mixtures, this section augments Section 12 in R 35.

X2.9.2. Improving Coating—Most WMA processes involve complex chemical reactions, thermodynamic processes, or both. Consult the WMA additive supplier for methods to improve coating.

X2.9.3. Improving Compactability—Most WMA processes involve complex chemical reactions, thermodynamic processes, or both. Consult the WMA additive supplier for methods to improve compactability.

P

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X2.9.4. Improving the Tensile Strength Ratio—Some WMA processes include adhesion promoters to improve resistance to moisture damage. Consult the WMA additive supplier for methods to improve the tensile strength ratio.

X2.9.5. Improving Rutting Resistance—The rutting resistance of WMA can be improved through changes in binder grade and volumetric properties. The following rules of thumb can be used to identify mixture adjustments that improve rutting resistance.

Increasing the high-temperature performance grade by one grade level improves rutting resistance by a factor of 2.

Adding 25 to 30 percent RAP will increase the high-temperature performance grade by approximately one grade level.

Increasing the fineness modulus (sum of the percent passing the 0.075-, 0.150-, and 0.300-mm sieves) by 50 improves rutting resistance by a factor of 2.

Decreasing the design VMA by 1 percent will improve rutting resistance by a factor of 1.2.

Increasing Ndesign by one level will improve rutting resistance by a factor of 1.2.

Note X25—These rules for mixture adjustment are documented in NCHRP Report 567: Volumetric Requirements for Superpave Mix Design.

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X2.10. Additional Reporting Requirements for WMA:

X2.10.1. For WMA mixtures, report the following information in addition to that required in R 35.

X2.10.1.1. WMA process description;

X2.10.1.2. Planned production temperature;

X2.10.1.3. Planned field compaction temperature;

X2.10.1.4. High-temperature grade of the recovered binder in the RAP for mixtures incorporating RAP;

X2.10.1.5. Coating at the design binder content;

X2.10.1.6. For Superpave mixtures the gyrations needed to reach 92 percent relative density for the design binder content at the planned field compaction temperature and 30°C below the planned field compaction temperature; For Superpave5 mixtues the gyrations needed to reach 95 percent relative density for the design binder content at the planned field compaction temperature and 30°C below the planned field compaction temperature;

X2.10.1.7. Gyration ratio;

X2.10.1.8. Dry tensile strength, tensile strength ratio, and observed stripping at the design binder content; and

X2.10.1.9. Flow number test temperature and the flow number at the design binder content.

1 Formerly AASHTO Provisional Standard PP 28. First published as a full standard in 2004.

G

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Susan Sillick Research Programs Manager | Engineering Division Montana Department of Transportation 2701 Prospect Avenue P.O. Box 201001 Helena, MT 59620 406-444-7693 [email protected] Web: http://www.mdt.mt.gov/research/ Follow Us: mdt.mt.gov

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AASHTO Committee on Materials and Pavements (COMP) TS 2d August 2020 Annual Meeting – Virtual

Initial Discussions - RTrack Test Method

Contributors: W. Griffin Sullivan (MDOT)

Ben Cox (USACE-ERDC), Wade Collins (PTI, Inc.) Ashley Carey (MSU), Jessica V. Lewis (MSU),

Isaac L. Howard (MSU) – Presenter – [email protected] History:

In 1990’s, Dr. Tom White developed PURWheel at Purdue – it was donated to MSU in 2007 – photo 1 PURWheel was re-furbished, some new protocols/features were evaluated, used for 10 years, and

discarded – photos 2 &3 – main reference: Rutting and Moisture Damage Resistance of High Reclaimed Asphalt Pavement Warm Mixed Asphalt: Loaded Wheel Tracking vs. Conventional Methods in AAPT

Present:

A few features of PURWheel remain, but several items changed, so decision was made to rename RTrack (Rubber Tire Wheel Tracker) to avoid confusion – the unit is commercialized as of 2019 – photos 4 & 5.

RTrack is primarily intended to improve the ability to assess moisture susceptibility of mixes – Hamburg DOES NOT measure effects of moisture only, splitting tensile methods are prone to combined effects cancelling results, boil test is approximate… i.e. a better moisture assessment would be useful, and RTrack can provide rutting resistance (dry), overall resistance in presence of moisture (wet), and effects of moisture (wet – dry) with a loaded rubber wheel (90 to 95 psi contact pressure).

Future (as proposed by contributors):

Ideally a few interested states form a task force to provide feedback as work unfolds over next year or more. IF, work progresses in a manner of interest to AASHTO, a draft method could be developed on a timeline

agreeable to task force, and a sub-committee ballot could then be initiated at a suitable time (at least a year from now, probably more than a year away) – today was to make AASHTO TS 2d aware of this work.

Photo 1 Photo 2

Photo 3

Rubber Tire

Asphalt Slab

Rut

Dep

th

Passes

Wet/Dry Ratios @ 5k & 12.5k Passes

Stripping InflectionPoint (SIP)

Wet Test Submerged in 64 oC Water

Dry Test 64 oC Air

P12.5

P12.5

Photo 4 Photo 5

AASHTO Committee on Materials and Pavements (COMP) TS 2d August 2020 Annual Meeting – Virtual

Request to Initiate Proposed Modifications to TP 108

Contributors: W. Griffin Sullivan (MDOT), Alex Middleton (MDOT)

Ben Cox (USACE-ERDC), Braden Smith (Hunt Refining) Rabeea Bazuhair (UAQU), Jonathan Easterling (MSU)

Isaac L. Howard (MSU) – Presenter – [email protected] APAC-MS (A CRH Company) and Ergon A&E

Presentation Goals:

1. Emphasize that abrasion loss testing (aka Cantabro Mass Loss) is an emerging technique that has value beyond just porous friction course (PFC) mixes. Mississippi has been a leading state in evaluating CML testing with dense graded asphalt (DGA) for the past decade – thousands of experiments including unaged, laboratory conditioned, and field aging environments have been tested.

2. Discuss possibility of updating TP 108 to include more DGA language, and add an appendix of optional lab conditioning protocols to be used with abrasion loss testing to assess oxidation, moisture, freeze-thaw, or combined effects of multiple environmental mechanisms.

Major Observations from Mississippi’s Abrasion Loss Testing:

1. Combined environmental effects are not well captured with many existing methods – e.g. oxidation and moisture can cancel when doing indirect tensile testing – aging is more than any one mechanism.

2. Current laboratory conditioning protocols/test method combinations are not harsh enough – e.g. R30-02 (2019) DOES NOT simulate 7-10 years of aging in Mississippi (or elsewhere according to literature).

3. 5 days of 85 oC air, 14 days submerged in 64 oC water, and a freeze-thaw cycle followed by abrasion loss testing has simulated 4 to 7 years of field aging in Mississippi (multiple mixes have been assessed).

4. Cantabro testing of DGA has successfully detected binder grade, presence of polymer, SBS vs. GTR, aggregate type, RAP content, air voids, effective binder volume, and aging.

Proposed Timeline: IF agreeable to TS 2d, a full draft of a re-worked TP 108 with language about testing of DGA with an

associated lab conditioning protocols appendix would be submitted for review by July of 2021. Key References (available upon request) State of Knowledge for Cantabro Testing of Dense Graded Asphalt, J. of Materials in Civil Engineering. Comparing Laboratory Conditioning Protocols to Longer-Term Aging of Asphalt Mixtures in the

Southeast United States, J. of Materials in Civil Engineering. Combined Effects of Oxidation, Moisture, and Freeze-Thaw on Asphalt Mixtures, Trans. Res. Record.

0 1 2 3 4 5 6 7 8

Years of Field Aging

Tensile Strength

Abrasion Loss