rap, ras and durable asphalt pavements
TRANSCRIPT
www.wrsc.unr.edu
RAP, RAS and Durable Asphalt Pavements
Adam Hand, PhD, PEPavement Engineering and Science Program
University of Nevada, Reno
CalAPA Fall ConferenceSacramento, CA – October 27, 2016
www.wrsc.unr.edu
What’s Up With Recycled Materials Use inand Durability of HMA?
• NAPA
• Nationally
– FHWA
Binder ETG
Mixture ETG
TFHRC
– TRB Annual Meeting
– NAPA Annual Meeting
– AAPT Annual Meeting
– NCHRP Projects
“The Pendulum Swung
Too Far and We Need to
Get Durability Under
Control “
www.wrsc.unr.edu
How is HMA Durability Improved?
• Raw Materials
– Aggregates - Contribute to Cracking Resistance?
– Asphalt Binder
Stiffness + Ability to Relieve Stress + Aging Sensitivity
• HMA Design
– Binder Content
Higher the Better, VMA, Gsb vs. Gse if using RAP/RAS
– Denser Mix Types
• Construction
– In-place Density ≤ 8%
www.wrsc.unr.edu
Where is the Pendulum Headed?
• Mid 1990’s Superpave without Performance Indicator Tests
• Early 2000’s Rutting and Moisture Sensitivity Focus
– Hamburg Wheel Track Device Proliferation
– More Fine Graded Mixtures
• Late 2000’s Economic Collapse and Escalating Binder Costs
– Increased Competition/Collapsing Margins
– Recycling Focus and Push
• Mid 2010’s Mix Durability WITHOUT Forgetting Rutting
• Late 2010’s BMD and Moderate Recycled Materials
www.wrsc.unr.edu
Outline
• RAP & RAS Use
• Agency & Industry Responses
• AASHTO Standards & Related NCHRP Projects
• Performance
• Trends - Our Future?
www.wrsc.unr.edu
2014 NAPA Annual Survey
• 2015 Survey Soon
• 2014 Trends
Continued?
www.wrsc.unr.edu
Count of State DOT Allowable RAP Percentages
• 2013 to 2014 Reduction in 10-20% & Increase in 20-30+%
• 4 DOTs > 30% RAP, 2 Since Reduced
www.wrsc.unr.edu
FHWA MemoOctober 2014
• Premature Cracking
• High Recycled Binder
Content
– RAP & RAS
– RAS
www.wrsc.unr.edu
Caltrans MemoJune 2016
• Premature Cracking
Failures
• Caltrans NSSP
– >15% RAP
– Blending Charts
www.wrsc.unr.edu
2015 Caltrans SS & NSSP on %RAP & %ABR
Type A HMA Location in Pavement
Allowable ABR (%)
2015 Standard Specification (RSS 05-06-16)
NSSP
Upper 0.2’ (Surface Courses)
= 25% n/a
Below 0.2’ (Intermediate or Base Courses)
= 40% n/a
Reference and Levels PG Required
2015 Standard Specification (RSS 05-06-16)
NSSP
%RAP
= 15% Specified PG n/a - silent
>15% = 25% As specified
or -1 PG by REQUEST
Blending Charts & Meet Specified PG
>25% = 40% Does not allow > 25% RAP n/a - silent
%ABR >0% = 25%
As specified or
-1 PG by REQUEST n/a - silent
>25% = 40% -1 PG REQUIRED n/a - silent
www.wrsc.unr.edu
Current NCHRP Projects
• Many Related to High ABR Performance, RAP, RAS, Aginghttp://www.trb.org/NCHRP/NCHRPProjects.aspx
www.wrsc.unr.edu
NCHRP Project Highlights• 09-52 Short-term Laboratory Conditioning of Asphalt Mixtures
– Lab mix short-term aging underestimates field aging
• 09-54 Long-term Aging of Asphalt Mixtures for Performance
Testing and Prediction
– AASHTO R30 Lab mix long-term aging (compacted mix at 85°C for 5
days) significantly under estimates long-term field aging
– Preliminary - Loose mix oven aged at 95°C for 5 to 25 days
• 09-58 Effect of Recycling Agents on Asphalt Mixtures with High
RAS & RAP Binder Ratios
– RA’s not Equal, ΔDose Rutting/Cracking, Aging Susceptibility
Diminishes Effectiveness, Compatibility, Binder Availability
• 09-61 Short- and Long-term Binder Aging Methods
– Replace or Modify T240 and R28
www.wrsc.unr.edu
Current AASHTO Standards
• AASHTO M320 PG Binder Grading
– AASHTO T240 Short-term Binder Aging (RTFO)
– AASHTO R28 Long-term Binder Aging (PAV)
• AASHTO M323 Superpave Mix Design
– AASHTO R30 Short-term Mixture Aging
– AASHTO R30 Long-term Mixture Aging
• AASHTO MP15 Recycled Asphalt Shingles
– AASHTO PP78 RAS in HMA
NCHRP 9-61
NCHRP 9-61
NCHR 9-52
NCHRP 9-54
PP78
RevisionsSignificant Change is Coming – Not Bad, but
Different
www.wrsc.unr.edu
AASHTO PP78 Changes before SOM
• Increase %AC over Optimum
– 0.1%AC per 2%RAS
• ΔTc ≤ -5°C
– On Blended Virgin/RAS Binder
What is Virgin Binder ΔTc?
What is RAP/RAS/Virgin Binder ΔTc?
www.wrsc.unr.edu
What is RAP Stiffness Range in California?
• Consider Climate
– Central and North Coast
– San Joaquin Valley
– Southern Deserts
• PG76-16 to PG100-4
– 4 PGs so 4x Stiffness
and ?x Embrittlement
• Is Cracking Similar in the
Different Environments?
www.wrsc.unr.edu
High ABR HMA Performance Observations
• NCHRP Report 752
• Illinois DOT
• FHWA ALF
• NCAT
• Nevada
• MinnRoad
• WiscDOT
– Mathey
www.wrsc.unr.edu
Current Focus – High ABR Mixes
• What is High Asphalt Binder Replacement?
– >25% Virgin Asphalt Binder Replacement with RAP, RAS, or RAP&RAS
• %ABR = %Asphalt Binder Replacement
– Specs Changing to %ABR from %RAP or %RAS
– Why?
%AC in 25% Coarse RAP ≠ %AC in 25% Fine RAP
RAP with 4% vs. 5.5%AC
Tear-off RAS vs. Manufacture Waste RAS
…
• Why Does It Matter?
– ↑ %ABR = ↑ Binder Stiffness + ↓Stress Relaxation
– High Stiffness/Low Stress Relaxation = Cracking and Durability Issues
www.wrsc.unr.edu
IL DOT →FHWA ALF High Binder Replacement Mixtures
• FHWA Memos – High ABR, RAS and REOB Warning to DOTs
• FHWA lllinois DOT Memo
– http://www.youtube.com/watch?v=zJv2oZG2Mys
• Illinois DOT Reduced %ABR
– 40% to 25% Base Mix
– 40% to 15% Surface Mix
– 40% to 10% PMA Mix
• FHWA ABR RESEARCHRAP, High RAP, RAS, RAP+RAS
Sections with and without PG Grade
Drops
www.wrsc.unr.edu
FHWA ALF – Like HVS used in California
• Simulated Truck Loading and Pavement Temperature
• 35,000 Load Cycles per Week
• 7k to 19k Wheel Load
www.wrsc.unr.edu
FHWA ALF Cycles to 200” of Cracking
0
50
100
150
200
250
300
350
400
450
L1: 0% ABRControl PG64-
22
L9: 20% ABRRAP PG64-22Foamed WMA
L4: 20% ABRRAP PG64-22
WMA Evotherm
L6: 20% ABRRAP PG64-22
L11: 40% ABRRAP PG58-28
WMA Evotherm
L3: 20% ABRRAS PG64-22
L5: 40% ABRRAP PG64-22
AL
F C
ycle
s t
o 2
00
" C
rackin
g
Lane and Material
www.wrsc.unr.edu
FHWA ALF Crack Life Ratio
100
73
38
3028
16
11
0
10
20
30
40
50
60
70
80
90
100
L1: 0% ABRControl PG64-
22
L9: 20% ABRRAP PG64-22Foamed WMA
L4: 20% ABRRAP PG64-22
WMAEvotherm
L6: 20% ABRRAP PG64-22
L11: 40% ABRRAP PG58-28
WMAEvotherm
L3: 20% ABRRAS PG64-22
L5: 40% ABRRAP PG64-22
Cra
ck L
ife
Ra
tio
(%
)
Lane and Material
www.wrsc.unr.edu
FHWA ALF Findings
• Use of Recycled Materials Significantly Impacts Cracking
(Fatigue) Performance
– Virgin, low RAP, high RAP, RAS
• Grade Bumping Down improves Performance Slightly
• Foaming helps with low RAP at WMA Temperatures
• FHWA Determining How Much “Additional Virgin Binder over
Optimum is Need for Recycle Mixes” to Achieve Equal
Cracking Performance to Virgin Mix
– VTRC (VDOT)
≈ 0.1%/10% RAP ABR
≈ 0.X/10% RAP ABR
www.wrsc.unr.edu
RAP/RAS Compatibility with Polymer Modified Asphalt Binders
• NCAT Test Track
– Florida DOT Top Down Cracking
RAP and RAS
• Nevada
– RAP Only
www.wrsc.unr.edu
NCAT Test Track (FDOT top down cracking test sections)
• 2 Mile Oval, Conventional Construction, Highway Trucks
• 4 Mix/Binder Combinations
• No Distress Except Top Down Cracking at 10M ESALs
PMA-0%
RAP
GTR-0%
RAP
PMA-20%
RAP
PMA-20%
RAP + 5%
RAS
www.wrsc.unr.edu
NCAT Test Track (FDOT top down cracking test sections)
0
10
20
30
40
50
60
70
80
90
100
0 2000000 4000000 6000000 8000000 10000000 12000000
Perc
ent
Lane C
rackin
g
Traffic (ESALs)
PMA-0% RAP
GTR-0% RAP
PMA-20% RAP
PMA-20% RAP + 5% RAS
“Stiffer polymer-
modified binders
should not be used
in conjunction with
RAP/RAS mixtures
because this causes
mixes to be too stiff”
www.wrsc.unr.edu
Other NCAT Technology News Updates
• 2016 “Go to” Florida DOT high traffic mix
– PG76-22 (No RAP/RAS Allowed)
• Michigan DOT
– Design Air Voids = 3% to increase Optimum %AC
• Colorado DOT
– Revised Section 403
– CDOT has ability to adjust contractor mix design optimum %AC
up & only fine graded mixes or SMA for surface course to
improve Durability
www.wrsc.unr.edu
Nevada Study
• Aggregate Source & Blend
• 3 RAP Sources
• 2 PG Binder Grades
• All Properties – Just Fatigue Here
www.wrsc.unr.edu
Influence of %RAP on Fatigue of Mixes with Polymer Modified Binder
30
0,0
00
1,2
00
,00
0
4,5
00
,00
0
www.wrsc.unr.edu
Nevada Study
100
4 2
14
51
3 2
0
10
20
30
40
50
60
70
80
90
100
Fatigue
LIfe R
atio
www.wrsc.unr.edu
Backgroud
• Concerns with long term pavement performance related to
binder durability is not new
Predates Superpave & PG binders
Focus of many studies simply related to binder aging
• Asphalt Institute - Anderson 2011 – REOB Concerns
– Rheological & ductility of PAV binders and binders recovered from
aged field mixtures
– Relationship to non-load associated distress
–ΔTc of 2.5°C = cracking warning limit, ΔTc = 5°C
point where binder durability lost
www.wrsc.unr.edu
Fatigue
Cracking
Rutting
PAV - aging
RTFO - aging
No aging
Time
Construction
[RV] [DSR]
Low Temp
Cracking
[BBR]
[DTT]
Superpave PG Binder Specification
www.wrsc.unr.edu
Binder Relaxation Properties
• Bending Beam Rheometer measures Stiffness and m value
• BBR m value measures relaxation or ability of binder to
relieve stress at cold temperatures
• As binder ages m value continues to decrease indicating loss
of relaxation properties (embrittlement) while the stiffness
increase levels off
• ΔTc is an indicator of embrittlement = difference in temp
where S = 300MPa and m value = 0.3
www.wrsc.unr.edu
ΔTc Concept for REOB/CrackingWhat is ΔTc ?
• ΔTc=BBR S Tcritical – BBR m Tcritical
• Is negative value for m-controlled binders
• 2xPAV
980 mN (100 g) Load
Asphalt Beam
Deflected PositionAsphalt Beam
Original Position
www.wrsc.unr.edu
So Why is Any of This Important?
• As Binders age they lose the ability to relax stresses,
mechanical or thermal
– Stiffness Increases
– Ductility Decreases
– Brittleness Increases
• Having a means of identifying when we can expect field
problems would be worthwhile
Spread between BBR S & m Tcritical values increase, ΔTc
becomes more negative
www.wrsc.unr.edu
Blending Charts – Do they help? Are they enough?
0 20 40 60 80 100
100 80 60 40 20 0% RAP
% New
Vis
co
sity o
r G
*/S
in
of R
AP
Bin
de
r (O
ld)
Vis
co
sity o
r G
*/S
in
of V
irg
in B
ind
er
(Ne
w)
Spec Limits
10-25% RAP
Percentages of Virgin and RAP
Material
www.wrsc.unr.edu
Comparative Crude Source Study
• 2006 Mathy constructed 5 test sections for MNDOT on
Olmsted CTH 112 near Rochester, MN
– 3 test sections compared performance of 3 different crude sources
of the same PG Grade, all (NEAT)
PG 58-28 Source #1, 0% RAP
PG58-28 Source #2, 0% RAP
PG58-28 Source #3, 0% RAP
– 2 test sections compared PG 58-34 PMA (0% RAP) and PG 58-34
(NEAT) + 20% RAP
www.wrsc.unr.edu
0.0
4.0
8.0
12.0
16.0
20.0
24.0
PG58-34(neat)+20% RAP
PG58-34(PMA)+0% RAP
PG58-28 S1(neat)+0% RAP
PG58-28 S2(neat)+0% RAP
PG58-28 S3(neat)+0% RAP
Lo
ng
itu
din
al/T
ran
svers
e C
rackin
g,
mF
ati
gu
e C
rac
kin
g,
m2
MN CTH 112 Cracking Data4 Years
Transverse Longitudinal Fatigue
www.wrsc.unr.edu
0.0
4.0
8.0
12.0
16.0
20.0
24.0
PG58-34(neat)+20% RAP
PG58-34(PMA)+0% RAP
PG58-28 S1(neat)+0% RAP
PG58-28 S2(neat)+0% RAP
PG58-28 S3(neat)+0% RAP
Lo
ng
itu
din
al/T
ran
svers
e C
rac
kin
g,
mF
ati
gu
e C
rackin
g,
m2
MN CTH 112 Cracking Data5 Years
Transverse Longitudinal Fatigue
www.wrsc.unr.edu
0
50
100
150
200
250
300
350
400
450
500
550
-7.0 -6.0 -5.0 -4.0 -3.0 -2.0 -1.0 0.0 1.0 2.0
To
tal
Cra
ckin
g,
m
ΔTc of Recovered Binder from Cores (Top 1/2")
MN CTH 112 Cracking DataTotal Cracking vs. ΔTc of Recovered Binder (8 Years)
PG58-28 S2 (neat)+0%
RAP
PG58-34 (PMA)+0%
RAP
PG58-28 S1 (neat)+0%
RAP
PG58-28 S3 (neat)+0%
RAP
www.wrsc.unr.edu
MnROAD Test of 3 Binders
• Constructed September 1999
• 3 Binders
– PG 58-28
– PG 58-34
– PG 58-40
• Trafficked until April 2007
• Annual Distress Surveys Conducted
www.wrsc.unr.edu
MnROAD COMPARATIVE BINDER STUDY
58-28
58-34
58-40
y = -160.85x - 417.74R² = 0.9957
0
100
200
300
400
500
600
700
800
900
1000
-9.0 -8.0 -7.0 -6.0 -5.0 -4.0 -3.0 -2.0 -1.0 0.0
LIN
EA
R F
EE
T O
F C
RA
CK
ING
ΔTc, °C
5.5 year total cracks (Non CL) = F(ΔTc 40 hr. PAV)
5.5 year total cracks (Non CL) Linear (5.5 year total cracks (Non CL))
RATIO CRACKS IN YEAR 5.5 TO YEAR 4
BINDER YEAR 5.5 YEAR 4 RATIO
58-28 126 20 6.3
58-34 13 0 ∞58-40 924 77 12
58-28
58-34
58-40
y = -12.935x - 29.753R² = 0.9946
0
10
20
30
40
50
60
70
80
90
-9.0 -8.0 -7.0 -6.0 -5.0 -4.0 -3.0 -2.0 -1.0 0.0
LIN
EA
R F
EE
T O
F C
RA
CK
ING
ΔTc, °C
4 year total cracks (Non CL)=F(ΔTc 40 hr PAV AGED BINDER)
4 YEAR TOTAL CRACKS (NON CL) Linear (4 YEAR TOTAL CRACKS (NON CL))
www.wrsc.unr.edu
Findings
• Blending Charts and ΔTc Provide DIFFERENT Answers
• ΔTc < -5°C (i.e. more negative) for the 40 hour PAV is
associated with the increased levels of pavement distress
after approximately 5 years of service
• Use of some blend additives can accelerate the decrease of
ΔTc at equal dosage levels
– This is exacerbated when trying to accommodate high RAP
&/or RAS binder replacement levels
• Use of RAS in mixes at levels ≈ 4% will significantly
accelerate the decrease in ΔTc as mixes age
www.wrsc.unr.edu
Gerry’s Comments
• All asphalt binders are not created equal
– Crude source—which dictates compositional makeup
affects long term performance
– We all know this and yet are perplexed when OUR
pavement doesn’t ALL perform well
– Not all binders are refined to grade, more likely today than
previously
– In some cases binders are post refining blends of stiffer
materials with lower stiffness VTB’s or gas oil
– Non asphaltic materials are being used to produce finished
binders (petroleum oils, bio-based oils, PPA, various types
of polymers)
www.wrsc.unr.edu
Our Future?
• ABR used vs. % RAP or %RAS• Allowable %RAP ABR↓ likely
15-25%?• Allowable %RAS ABR↓↓↓ or Disallowed
2-3%• RAP &/or RAP with PMA ↓↓↓ or Disallowed• Allowable RAP &/or RAS different for
– Surface vs. Base Mixes• REOB Disallowed &/or ΔTc in Specs (NE & SE)
– Especially if RAP &/or RAS Mixes• “Balanced” Mix Design
– New Lab Aging Conditions in Mix Design
– “Optimum %AC+”
www.wrsc.unr.edu
Balanced Mix DesignVolumetrics + Rutting/MS Test + Cracking Test
• Raw Material Properties• Volumetrics
DC
T?
SC
B?
Rutting/MS
HWTD?
DurabilityAt What
Temp?
At What
Temp?
www.wrsc.unr.edu
Leading Edge
• RAS
– 1X State DOT’s
• REOB/ ΔTc
– NEAUPG
– SEAUPG
• Balanced Mix Design
– NAPA Durability Committee
– FHWA Mix ETG BMD Taskforce
– State DOT’s
Louisiana, Illinois, New Jersey, Wisconsin (almost)
www.wrsc.unr.edu
Our Industry Responsibility - Get It Right
• Agencies
• Producers/Contractors
• Associations
• Academia
Our
Industry
Our
Responsibil
ity
www.wrsc.unr.edu
92nd AAPT Annual Meeting and Technical
Sessions
The 2017 Annual Meeting will be held March 19-22,
2017
The Island Hotel, Newport Beach, California USA2017 Annual MeetingThe Annual Business Meeting and Technical Sessions of the
Association of Asphalt Paving Technologists (AAPT) will be March 19-
22, 2017 in Newport Beach, California at The Island Hotel
(www.islandhotel.com). The annual meeting includes asphalt-related
technical sessions comprised of peer-reviewed papers, and invited
presentations on specific topics in the Leading Edge Workshop, AAPT-
ISAP International Forum, and Symposium. Please see the Annual
Meeting page (http://asphalttechnology.org/annual-meeting.html) for
more details as they become available.
Important datesAugust 15, 2016 - deadline for submitting papers (CLOSED)
October 10, 2016 - peer reviews completed
November 4, 2016 - notification of paper acceptance
December 2016 – Annual Meeting registration opens
March 19 to 22, 2017 - Annual Business Meeting and Technical Sessions
Our 2017
venue
For the latest information please check our web site at: http://www.asphalttechnology.org
AAPT Office:6776 Lake Drive, Suite 215
Lino Lakes, MN 55014
Phone: 651-293-9188
Fax: 651-293-9193 or Email: [email protected]
www.wrsc.unr.edu
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html
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