field evaluation of asphalt rubber pavements in texas · pdf file3 evaluation of asphalt...

Evaluation of Asphalt Rubber Pavements in Texas

Prepared for: Rubber Pavements Association

Tempe, Arizona

Prepared by:

Maghsoud Tahmoressi, P.E.

PaveTex Engineering and

January 2001

M
T
Testing, Inc.

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Table of Contents Page 1. Introduction…………………………………………………………. 3

2. Project Selection…………………………………………………….. 4

3. Pavement Evaluation Method……………………………………… 4

4. Findings……………………………………………………………… 6

Hot Mix

Porous Friction Course

Chip Seal

5. Conclusions…………………………………………………………. 9

6. Acknowledgment…………………………………………………... 10

Appendix A: Hot Mix Projects

Appendix B: Porous Friction Course Projects

Appendix C: Chip Seal Projects

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Evaluation of Asphalt Rubber Pavements in Texas Introduction Texas has a long history of utilizing asphalt rubber in construction and rehabilitation of pavements. The first reported use of asphalt rubber in Texas was in 1976 by Bryan and El Paso Districts of Texas State Department of Highways and Public Transportation (now Texas DOT) (Ref. 1). In an extensive research project conducted by Texas A&M University in 1982, the researchers evaluated performance of nearly 800 Miles of seal coat and underseal constructed through out Texas from 1976 and 1981 (Ref. 2). The researchers concluded, “ asphalt rubber binders can be effectively used in seal coat construction to reduce alligator cracks and raveling when compared to conventional seal coat performance. However, shrinkage cracking and flushing performance is respectively equal and less desirable than conventional seal coat performance”. The research conducted at Texas A&M University also identified some of the short comings in design and construction practices which may have led to less than desirable performance with respect to flushing. The asphalt rubber as discussed in this report is the produced through the blending process know as the “Wet Process”. This process involves on-site blending of at least 15 Percent crumb rubber with asphalt cement. In Texas, asphalt rubber has been used in four different types of applications. These applications are:

1. Chip Seal Coat: In this application, asphalt rubber is used as the binder for the seal coat, which is the finished pavement layer. This application is also known as SAM (Stress Absorbing Membrane)

2. Underseal: In this application, asphalt rubber is used as the binder for chip

seal application. After construction of chip seal layer an asphalt overlay is applied on the chip seal layer. The function of this underseal is to waterproof the existing pavement and retard reflective cracking. This application is also know as SAMI (Stress Absorbing Membrane Interlayer).

3. Hot Mix: Asphalt rubber is used as the binder for hot mix. 4. Porous Friction Course (PFC): Asphalt rubber is used as the binder for open

graded Porous Friction Course. TxDOT has constructed several asphalt rubber projects in each of the above mentioned categories. The purpose of this report is to document performance of these existing asphalt rubber projects.

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Project Selection At the start of this project, criteria was set to evaluate only those pavements, that have been in service for more than five years, to allow some determination of long term performance potential. Due to the fact that there were limited number of either hot mix or PFC projects in the state, decision was made to evaluate all such projects, as long as they have not been reconstructed or rehabilitated. Some of these projects maybe less than 5 years old, but conducting this evaluation will provide a bench mark for any future evaluations that may be conducted. Asphalt rubber chip seal is considered to be a routine rehabilitation strategy in several districts of TxDOT, but a comprehensive statewide database does not exist for this product. To locate suitable projects, individuals from Cox Paving of Blanco, Texas and International Surfacing Systems (ISS) of Phoenix, Arizona were contacted. These two companies have been involved in construction of nearly all asphalt rubber projects in Texas. These companies were extremely helpful in providing records to locate existing asphalt rubber seal coat projects. A representative number of projects through out the state were selected for filed evaluation. In 1993 TxDOT conducted a comprehensive research project called the Supplemental Maintenance Effectiveness Research Program (SMERP). In this study, TxDOT constructed experimental sections in twenty sites around the state. Each site contained test sections including Asphalt Rubber chip seal, Microsurfacing, Polymer Modified chip seal, Latex modified chip seal, Conventional AC chip seal, and a fog seal. In each site one section was identified as Control and did not receive any rehabilitation. The purpose of this project was to evaluate relative effectiveness of these maintenance rehabilitation strategies. Several of these SMERP sections have been rehabilitated since 1993, but some of them are still in service. These sections allow not only an evaluation of performance of Asphalt Rubber chip seal, but also a direct comparison with other chip seal binders. Therefore we decided to include as many of these SMERP sections in this field evaluation as possible. Time and budget restraints did not allow evaluation of all existing SMERP projects. Pavement Evaluation Method Performance of asphalt rubber pavements was evaluated visually by recording the extent of occurrence and degree of severity of distresses such as cracking, surface deformation, surface defects, patching and miscellaneous distresses. Cracking was subdivided into the following categories: Fatigue, Longitudinal, Reflection, Transverse, Block and Edge cracking.

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Rutting and shoving were classified as surface deformation while raveling, bleeding, stripping and polished aggregates were classified as surface defects. The form shown below was used in rating each project and several photographs were taken at each site. In majority of the projects visited, a representative from the local TxDOT district accompanied the author during the site visit and the condition survey form was completed jointly.

Flexible Pavement Condition Evaluation Form

Interstate / Highway: District: Mix Type:

County: Date: Surveyed By:

Distress Type Severity Extent of OccurrenceCracking Slight Moderate Severe Intermittent Frequent Extensive

Fatigue CrackingLongitudinal CrackingReflection CrackingTransverse Cracking

Block CrackingEdge Cracking

Surface Deformation RuttingShoving

Surface Defects RavelingBleedingStripping

Polished AggregatesMiscellaneous Distresses Water Weeping

Patching and Potholes Patch/Patch DeteriorationPotholes

Comments.

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Findings As stated previously, the purpose of this study was to evaluate performance of existing asphalt rubber pavements. The findings of this study are summarized in the following sections for Hot Mix, Porous Friction Course, and Seal Coat Projects. Hot Mix Hot mix projects included in this study are shown in Table 1. Details regarding each project as well as pictures from projects are included in Appendix A. Table 2 present the available mix design information about the hot mix projects. The oldest projects evaluated were approximately 8 years old at the time of this evaluation. Prior to mid 1992, TxDOT did not have a special specification for crumb rubber modified hot mix. Therefore, the specification for conventional dense graded hot mix (TxDOT standard specification Item 340) was used along with necessary special provision to contract these projects. Either Type D (½” maximum size) or Type C (5/8” maximum size) mixes were used. All projects, which utilized Type D gradation, experienced premature failure. The Lubbock project (CPM 52-1-28) utilized the Type C grading. This project experienced raveling at an early age and was covered with a seal coat to stop the raveling. TxDOT made significant changes to mixture design procedure and specifications for crumb rubber modified hot mix in 1992. The gradation requirements were changed to utilize gap-graded mixtures instead of dense graded mixtures. Specification for in-place density was also modified in order to ensure adequate in place densities. With exception of the Lubbock project, all the projects shown in Table 1 were constructed under the new design procedure and specifications. The two projects in Lufkin district experienced premature failures. TxDOT personnel conducted a comprehensive forensic study on the Angelina County project (STP 93(142)R) . Excerpts from this study along with some of the findings are shown in Appendix A. This forensic study indicated that failure in Cement Stabilized Base was the primary cause of premature failure. There is no records of any comprehensive forensic study for the Lufkin District project in Nacogdoches County, however, TxDOT headquarters personnel evaluated this project in 1995, one-year after construction. The conclusion from this evaluation was that the premature failure could be associated with failure of base layer caused by water (Ref. 3) The hot mix project in Houston district (AR1965-1-5) has some cracking and patches in isolated areas. The cracking and patches appear to be only in fill sections. The cracks are very wide and deep, indicating excessive movement in base layer. This excessive movement is most likely caused by shrinkage of the base layer. The shrinkage is likely due to sever prolonged drought in the region. There was full depth repair and patching in several locations. The material used for patching is conventional dense graded Type D hot mix. There is severe cracking even in newly placed patches. This further reinforces the possibility that shrinkage in the base layer is causing overlay failures. Photos showing

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the comparison between cracking in AR overlay and Type D patches are included in Appendix A. As seen in these photos, the cracks in Type D patches are more sever than the AR overlay. With exception of distresses discussed above, the AR hot mix projects appear to be performing satisfactorily. Results of pavement evaluations and discussion with TxDOT district personnel indicate that AR hot mix projects have significantly better resistance to cracking than conventional hot mix. In addition these projects are exhibiting good resistance to rutting. Porous Friction Course (PFC) PFC projects represented in this study are shown in Table 3. Details regarding each project as well as pictures from the projects in Appendix B. As shown in Table 3, five projects have been constructed by TxDOT using asphalt rubber binder. The oldest project was constructed in 1994 in Odessa District. These pavements are all in excellent condition. Based on the pavement evaluation conducted for this study and discussions with Odessa and Lufkin district personnel, it is evident that crumb rubber modified PFC has better performance with respect to resistance to reflective cracking and resistance to raveling than conventional or polymer modified binders. This attribute is best demonstrated in the Lufkin district project on SH 146, where crumb rubber was removed from a portion of the project for comparison purposes. As shown in the photos in Appendix B for this project, the section with crumb rubber showed excellent resistance to reflective cracking, while in the section without crumb rubber, nearly every crack reflected through. One of the reasons for this improved resistance to cracking and raveling is the high amount of binder that can be used in crumb rubber modified PFC. For example, the binder content in Odessa district projects were 8.5 %. In the first PFC project in Odessa , Martin County, IM 20-1(129)158, the binder content was increased to 9.5 % for a limited quantity of mix that was placed on the shoulder. This experiment was conducted to determine resistance to drain down at high binder contents. The results indicated that even at 9.5 % the crumb rubber modified PFC did not show any signs of binder drain down. Ability to use high binder contents coupled with elastic properties of asphalt rubber significantly improves resistance to cracking and raveling. Seal Coat Total of 18 seal coat projects were evaluated in this study. List of Seal Coat projects represented in this study is shown in Table 4. Details regarding each project as well as pictures from the projects are included in Appendix C. The projects ranged from low volume Farm to Market roadways to sections of Interstate Highway 10 which carries heavy truck traffic. Five projects included test sections from the Supplemental Maintenance Effectiveness Research Program (SMERP). These projects provided a unique opportunity to compare performance of asphalt rubber binder to polymer modified, latex modified and non-modified asphalt binders, with all other factors being

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constant. Based on the evaluation of seal coat projects evaluated in this study, the following conclusions are made:

1. asphalt rubber seal coat has excellent resistance to reflective cracking. High binder application rate (0.5 to 0.6 gal/sq yd) coupled with elastic properties imparted by crumb rubber addition has proven to retard reflective cracking.

2. Some asphalt rubber seal coat projects evaluated in this study showed varying

degrees of bleeding. Projects with most likelihood of bleeding are those which utilize grade 4 ( ½” maximum size) chips. Small chip size along with heavy binder application will cause the chips to sink into the binder, thereby causing bleeding.

3. Asphalt rubber seal coat projects showed good chip retention.

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Conclusions Based on the conditions of this study and projects evaluated, the following conclusions are warranted.

1. All asphalt rubber Porous Friction Course (PFC) projects are exhibiting excellent performance properties. Resistance to cracking and raveling in asphalt rubber PFC is particularly impressive. From cost and benefits stand point, PFC represents the best application for asphalt rubber.

2. With exception of two projects in Lufkin district, all asphalt rubber hot mix projects that

utilized CMHB gradation are in satisfactory conditions. The Lufkin projects showed premature distress due to base failures.

Resistance to cracking exhibited in asphalt rubber CMHB exceeds the resistance to cracking typically expected of CMHB mixtures.

3. In seal coat projects which utilized grade 3 ( 5/8” maximum size) chips, resistance to cracking

and chip loss was excellent. These projects typically did not exhibit bleeding. However, when smaller chip size (i.e. grade 4) was used, bleeding was a common problem.

If it is necessary to use grade 4 chips, then the asphalt rubber application must be reduced to the extent possible to reduce bleeding. However, when asphalt rubber application rate is reduced, resistance to cracking will be reduced and chip retention will be diminished.

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Acknowledgments This project was conducted for Rubber Pavements Association. The author wishes to acknowledge the support provided by Cox Paving Company of Blanco, Texas and International Surfacing Systems of Phoenix, Arizona in locating the asphalt rubber projects and providing available project records. The support of Bituminous Branch of TxDOT Construction Division in obtaining mix design information for hot mix projects is appreciated. Several individuals from TxDOT districts accompanied the author in the field visits and provided invaluable information about history of asphalt rubber projects and assisted in rating the projects. Support of all these professionals is greatly appreciated.

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Table 1. List of Hot Mix Projects

Date District County Highway ADT Project CSJ Location

92 Lubbock Parmer US 84 3,300 CPM 52-1-28 52-1-28

From Lariat to Farewell, has been seal coated due to ravelling

92 Wichita Falls Wichita FM 369 14,900 CRP 91(42)M 802-02Southwest Parkway, From Ray Road to the Stadium

93 Abilene Callahan SH 36 5,400 STP 93(115)RM 0181-02-021

From Taylor Co line 6.8 Miles south east near FM 603

93 Lufkin Angelina SH 63 3,000 STP 93(142)R 0244-01-040From FM 2743 to the Jasper County Line

94 Lufkin Nacagdoches US 259 17,000 138-6-XX From US 59 North

94 Beaumont Hardin US 96 30,000 65-05-117

North side of Lumberton from West Chance Cutoff to Village Creek

95 Houston Fort Bend FM 1994 1,300 AR 1965-1-5 1965-001-005From SH 36 North to near intersection of FM 762

94 Odessa Ector IH 20 13,200 IM20-1(122)111 0004-07-087From Midland County line to West of FM 1936

98 Odessa Crane SH 385 4,700 STP 97(291)R 0600-03-016Starts S of Crane city limits, goes N to Crane Co. Line

99 Abilene Nolan IH 20 15,060 CPM 6-2-91

From Sweetwater to West of Roscoe, 9.3 Miles East Bound Lanes only

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Table 2. Mix Design Information For Hot Mix Projects District Abilene Beaumont Houston Lubbock Lufkin Odessa Odessa Wichita Falls AbileneCounty Callahan Hardin Fort Bend Parmer Angelina Crane Ector Wichita NolanHighway SH 36 US 96 FM 1994 US 84 SH 63 SH 385 IH-20 FM 369 IH 20Date Constructed 1993 1994 1995 1992 1994 1998 1994 1992 1999Spec. Item 3006 3006 3065 Item 340 3020 3006 Item 340 3092CSJ 0181-02-021 65-05-117 1965-001-065 52-1-28 0244-01-040 0600-03-016 0004-07-087Project STP 93(115)RM STP 94(106)R AR 1965-1-5 CPM 52-1-28 STP 97(291)R IM20-1(122)111 STP 91(42)R CPM 6-2-91Mix Type CMHB-C CMHB-C CMHB-C Type C CMHB-C CMHB-F CMHB-F Type D CMHB-FBinder Content, % 8 7.1 5.8 4.2 7.3 8.3 8.5 7 8.3Rubber Content, % NA 16 NA 19 15 16 16 19 17Binder Viscosity NA 4500 NA NA NA NA NA 2550 NASoftening Point NA ? NA NA NA NA NA 136 F NAAC Source NA Exxon AC-10 Exxon AC-20 NA NA Fina AC-10 Fina AC-10 Ker McGee AC-10 Fina AC-10Rubber Source NA Tires, Inc., Salem NC Granular Prod, Mexia NA Granular Products NA NA Tiregator, MexiaRubber Type NA Type III NA NA Type II, Buffings Type II Type II Type II Type II

Gradation, % Passing7/8" 100 100 100 100 100 100 100 100 1005/8" 99.4 93.4 98.1 99.8 99.7 100 100 100 1001/2" 100 100 100 99.93/8" 63.6 67.9 65.7 71 56.1 97.4 97.4 96 91.1# 4 36.8 35.9 34 46.3 32.3 46.7 46.6 50 40.6

# 10 14.7 17.9 18.6 31 17.2 16.9 16.9 30.4 18.9# 40 9.4 8 11.6 16.6 10.5 8.3 8.3 11.6 11# 80 7.1 6 9 6.8 7.9 6.5 6.3 5.1

# 200 5.1 4.5 7.1 2.2 6 5.4 5 2 6.9

Air Voids, % 3 3 3 4 3 3 3 4 3VMA, % NA 19 18 13 18.4 20.8 NA 15.2Creep Stiffness, PSI 7020 6354 10809 NA 7985 7409 6111 NA NACreep Slope, In./In./Sec 3 2.6 2.5 NA 3.2 0.24 0.44 NA NAPermanet Strain, In./In. 0.39 0.5 0.1 NA 0.5 4 3.7 NA NA

Aggregate Type Limestone Limestone Limestone Basalt Limestone Limestone Limestone Sandstone/ Limestone LimestoneAggregate Source Yates/ Bridgport Tower Rock, MO Redland Western, NM Redland, S.A. Jones Bros. Jones Bros. Dolese/ Perry

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Table 3. Porous Friction Course Asphalt Rubber Projects


94 Odessa Midland IH 20 11,200 IM 20-1(124)154 0005-03-054

IH-20 loop around Stanton. From Intersection of BI-20 West of town to 1 mile East of intersection of BI-20 East of town.

95 Odessa Martin IH 20 11,100 IM 20-1( 129 ) 158 0005-04-055

From end of CSJ 005-04-0054 to Howard County line

95 Lufkin Polk SH 146 8,300 STP 95(85)HEC,etc 0388-01-035,etc

South of Livingston. From Intersection of US 190 South to FM 1988

2000 Odessa Ward IH 20 5,900 0004-04-073From E of Monahans W to Pyote. First half

2000 Odessa Ward IH 20 5,700 0004-04-075From E of Monahans W to Pyote. second half

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Table 4. Asphalt Rubber Seal Coat Projects


92 Bryan Madison FM 247 1,250 CPM-475-3-44,etc 0475-03-044,etc

From Midway on FM 247 about 9.5 miles south to Bedios creek. One section on IH 45, about 2 miles south and 2 miles North of SH 21. This section may be SAMI (CSJ 0645-05-034)

92 Bryan Madison OSR, etc 470 CPM-475-3-44,etc 0475-03-044,etc

There are 9 different locations. Main locations on OSR From IH 45 to Midway about 14 miles. One section on IH 45, about 2 miles south and 2 miles North of SH 21. This section may be SAMI (CSJ 0645-05-034)

96 Childress Donely US 287 7,200 NH 96(11)R,etc 0042-07-045, etcUS 287 South Bound, From Clarendon to Hedly

89 El Paso Presidio US 90 770 Between Alpine and Marfa

95 El Paso Culberson IH 10 9,000Between Van Horn and IH 10/ IH 20 split

96 El Paso El Paso SH 20,etc 3,300 CPM2-3-16 etc 002-03-016, etc From Fabens S for about 12 miles96 El Paso El Paso FM 76 17,800 674-01-xxx From Loop 375 to FM 1109

2000 El Paso Culberson SH 54 210From Van Horn North to Guadalupe Mountain

95 Odessa Crane US 385 1,800 Between Crane and McCamey87 San Antonio Medina SH 173 1,350 0421-02-xxx Devine, From IH 35 S for 5 miles

88 San Antonio Bexar FM 1604 15,800

From SH 151 to US 90, AR chip seal is in turn lane, Info from S. Cox

91 San Antonio Bexar SP 536 12,300 CPM 17-1-31 0017-11-031 North of Bank Street

96 Wichita Falls Montague US 287 13,200 CSR 224-3-49 0224-03-49

US 287 from FM1125 just S. of Bowie North to Montague/ Clay Co. line

93 Amarillo Potter FM 1061 1,600 SMERP 4800-00-011 SMERP 4800-00-0110.75 mile E of FM 2381 to 2 mile E.

93 Odessa Ector FM 181 1,650 SMERP 4800-00-012 SMERP 4800-00-012Andrews Co. Line to 5.5 Miles N of SH 158

93 Odessa Martin SH 349 1,800 SMERP 4800-00-013 SMERP 4800-00-013Near FM 87 to Dawson Co. Line, Ref Marker 300 to 302, 48F06H

93 Brownwood Brown US 67 3,900 SMERP 4800-00-013 SMERP 4800-00-013Blanket Creek Bridge to 1.0 Mile N.

93 Brownwood McCullouch US 377 2,100 SMERP 4800-00-013 SMERP 4800-00-0131.0 Mile N. of FM 2996 S. to FM 2996

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References: 1. Texas Asphalt Rubber Survey, Rubber Pavement Association 2. Evaluation of Asphalt Rubber Membrane Filed Performance, Scott Schuler, Bob M. Galloway, and Jon

Epps, Texas Transportation Institute, Texas A& M University, Research Report 287-2, 1982 3. Review of Coarse Matrix High Binder Projects, Texas Department of Transportation, Materials and

Tests Division, 1995

Appendix A

Hot Mix Projects

Table 1. List of Hot Mix Projects


92 Lubbock Parmer US 84 3,300 CPM 52-1-28 52-1-28

From Lariat to Farewell, has been seal coated due to ravelling

92 Wichita Falls Wichita FM 369 14,900 CRP 91(42)M 802-02Southwest Parkway, From Ray Road to the Stadium

93 Abilene Callahan SH 36 5,400 STP 93(115)RM 0181-02-021

From Taylor Co line 6.8 Miles south east near FM 603

93 Lufkin Angelina SH 63 3,000 STP 93(142)R 0244-01-040From FM 2743 to the Jasper County Line

94 Lufkin Nacagdoches US 259 17,000 138-6-XX From US 59 North

94 Beaumont Hardin US 96 30,000 65-05-117

North side of Lumberton from West Chance Cutoff to Village Creek

95 Houston Fort Bend FM 1994 1,300 AR 1965-1-5 1965-001-005From SH 36 North to near intersection of FM 762

94 Odessa Ector IH 20 13,200 IM20-1(122)111 0004-07-087From Midland County line to West of FM 1936

98 Odessa Crane SH 385 4,700 STP 97(291)R 0600-03-016Starts S of Crane city limits, goes N to Crane Co. Line

99 Abilene Nolan IH 20 15,060 CPM 6-2-91

From Sweetwater to West of Roscoe, 9.3 Miles East Bound Lanes only

PavTex Engineering and Testing, Inc. Lobbock US 84-1

Highway: US 84 County: Parmer District: Lubbock Project: CPM 52-1-28 CSJ: 52-1-28 Project limits: From Lariat to Farewell Project Rating : Good Moderate reflective cracking, slight block cracking This is the last remaining dense graded AR hot mix projects. The project was placed constructed in 1992,using TxDOT Type C dense graded hot mix specifications. The total binder content for the project was ver y low. The mixture started to ravel almost immediately after construction. Therefore a seal coat layer was placed over AR hot mix to protect it from raveling. There are transverse cracks in the pavement with 50 to 60 feet spacing. In some isolated areas transverse crack spacing is getting smaller, and block cracking pattern is beginning to emerge.

PaveTex Engineering and Testing, Inc. Wichita Falls, FM 369-1

Highway: FM 369 County: Wichita District: Wichita Falls Project: CRP 91(42)M CSJ: 802-02 Project limits: Southwest Parkway From Rhea Road to the Stadium Project Rating: Good Moderate Reflective cracking in Transverse Direction, Intermittent patches This is a heavily traveled road in urban setting. AR Overlay was placed over a badly cracked HMAC layer. The existing HMAC was milled prior to AR overlay. Reflective cracking in AR overlay is mostly transverse with 10-30 feet crack spacing. There are few patches in the project, one near an intersection. Most intersections are flat with no rutting. AR overlay has performed well in this location considering the condition of the pavement upon which it was placed.

PaveTex Engineering and Testing, Inc. Abilene SH 36-1

Highway: SH 36 County: Callahan District: Abilene Project: STP 93(115)RM CSJ: 0181-02-021 Project limits: From Taylor County line 6.8 Miles South East to near FM 603 Project Rating: Excellent No rutting, transverse cracks at approximately 60 feet spacing. Transverse cracks are more frequent in the shoulder. Good ride and surface texture. This Asphalt Rubber Hot Mix project has CMHB-C gradations. The project is in excellent condition and has good ride. There is minor reflective cracking in the project, mostly transverse cracks. No rutting or raveling in project.

PaveTex Engineering and Testing, Inc. Abilene SH 36-2

View of AR section

AR surface texture

PaveTex Engineering and Testing, Inc. Lufkin, Angelina County, SH 63 -1

Highway: SH 63 County: Angelina District: Lufkin Project: STP 93(142)R CSJ: 0244-01-040 Project limits: From FM 2743 to the Jasper County Line Project Rating: Did not visit this project Premature Failures The asphalt rubber hot mix was a CMHB gradation and was placed to a depth of 1.5 inches in a 14 miles section of SH 63 from FM 2743 to the Jasper county line. This overlay was placed in 1993 and premature failures appeared in 1997. The failure was in form of rutting and shoving in the outer wheelpath, particularly in the northbound direction. In several spots asphalt rubber hot mix debonded and separated from its underlying dense graded hot mix. The asphalt rubber overlay covered the results of two previous rehabilitation efforts in this 14 Miles stretch of SH 63. These rehabilitation projects consisted of pulverizing the existing HMAC surface, blending it with existing granular base, cement treating the new base materials to a depth of 9”, applying a seal coat and surfacing with 3” of Type B dense graded HMAC. This rehabilitation was applied only to the driving lanes. The shoulder had a lesser structural section. It consisted on 2.5” conventional hot mix over 10” of Lime Stabilized base. About 12” of shoulder extended into the driving lane. Therefore the left wheel path, where most of the failures occurred was over the shoulder. The entire roadway was overlaid with 1.5” asphalt rubber hot mix. TxDOT conducted an in-depth forensic investigation to determine the causes of premature failure. The following is a portion of the findings documented in the forensic report “ The primary failure mechanism appears to be related to the highly absorptive nature of the aggregates used in the Cement Stabilized Base (CSB)… Moisture in the base appears to be breaking the cementitious bonds in the CSB layer. Once this layer is weakened, the overlying Type B HMAC is subjected to greater fatigue, producing fatigue cracking and pumping of fines from the CSB under traffic loads. Pressurized water, looking for an escape, attacks the asphalt bonds of the upper layers. The bond between the CMHB (asphalt rubber) and the Type B layer seems to be vulnerable to stripping, which allowed the CMHB layer to eventually work independently of the remainder of the pavement structure. When digging the test pits, large moisture concentrations were evident at the interface between the CMHB and the Type B HMAC layers where debonding had taken place. Once debonded, traffic loading exacerbated and accelerated rutting and shoving of this thin surface layer.” The forensic report also states “The CMHB layer thickness was between 0.90 and 1.10 inches thick on nearly 20 cores extracted; the design thickness was 1.50 inches. The CMHB layer is not considered a primary contributor to the noted failures”.

PaveTex Engineering and Testing, Inc. Lufkin, Nacogdoches County, US 259 -1

Highway: US 259 County: Nacogdoches District: Lufkin Project: ?? CSJ: 138-6-XX Project limits: From US 59 North Project Rating: Did not visit this project Premature Failures The asphalt rubber hot mix was a CMHB-C gradation using crushed siliceous river gravel. The overlay was completed in summer of 1994 and was exhibiting premature failures by December of 1995. The overlay was placed only on travel lanes and not on the shoulders. A brief site visit by TxDOT headquarters personnel in 1995 documented that there were potholes in the travel lanes and cracking and evidence of fines pumping out of the base. The conclusion from the site visit was that the premature failures could be associated with failure of the base layer caused by water ( Reference : Review of Coarse Matrix High Binder Projects, TxDOT, Materials and Tests Division, 1995) Author’s communications with the area engineer indicates that by the time of this report this project had experienced rutting in some areas. The outside lane and portions of the inside lane were milled and inlayed.

Fines From the Base layer pumping through the AR Hot Mix ( 1995 Picture, Courtesy TxDOT)

PaveTex Engineering and Testing, Inc. Beaumont, US 96-1

Highway: US 96 County: Hardin District: Beaumont Project: STP 94(106) R CSJ: 65-05-117 Project limits: North side town of Lumberton from W. Chance Cut off North to Village Creek Project Rating: Excellent No rutting, Few transverse cracks near W. Chance Road This Asphalt Rubber hot mix project was constructed as a test section in an overlay project which was primarily composed of Type C dense graded hot mix. The Asphalt Rubber portion of the project is at the North end of the job, North of West Chance Cut off in town of Lumberton. The AR section is in excellent condition, no rutting and only few transverse cracks near W. Chance Cut off. The type C section South of W. Chance Cut off which is the control for this project is showing both longitudinal and transverse cracking.


View of AR section

AR surface texture


Transverse and longitudinal cracking in Type C, control section.

PaveTex Engineering and Testing, Inc. Houston, FM 1994-1

Highway: FM 1994 County: Fort Bend District: Houston Project: AR 1965-1-5 CSJ: 1965-001-005 Project limits: From SH 36 N. to FM 762 Project Rating: Excellent Slight longitudinal cracking, some deterioration in fill sections in North end of the project This project is an AR hot mix overlay in a two-lane Farm-to- Market road in an urban area. The project starts from SH 36, majority of the project is in excellent condition. There is slight rutting in the left wheel path in isolated areas on the North end of the project near intersection of FM 361. At this intersection there is slippage of overlay, but no rutting. In the section North of FM 361, there is about a one mile long portion of the road that has been constructed as a fill section. This section is showing cracking in left wheel path on North bound lane and several patches in Southbound lane. This type of distress is limited to the fill section and stops past the bridge where the fill section ends. Picture shows one of the patches in the fill section in the fill area. The patch is a dense graded Type D hot mix. The same types of cracks are showing up in the patched area. The cracking in the patched area is more severe than the cracking in non-patched areas. This would indicate excessive movement of the base in the fill section. Picture shows the comparison of AR hot mix and the dense graded mix used for patching.


View of project near SH 36

AR hot mix surface texture


Segregation in isolated areas has caused slight rutting

Slippage near intersection of FM 361


Cracking in AR section in fill areas has led to rutting

Cracking in patched area


Severity of cracking in patched areas

Contrast between ar hot mix and type D hot mix used for patching.

Type D used for patching

AR Hot Mix

PaveTex Engineering and Testing, Inc. Odessa, Ector County, IH 20-1

Highway: IH-20 County: Ector District: Odessa Project: IM 20-1(122)111 CSJ: 0004-07-087 Project limits: From Midland Co. line to just W. of FM 1936 Project Rating: Excellent There is slight amount of longitudinal cracking. Moderate amounts of Transverse and Edge cracks in frequent locations. About 1/8” rutting in left wheel path of outside lane. This AR hot mix project has been in place since 1994. The underlying ACP was cracked and covered with an AR seal coat. Seal Coat was in service for one year before AR overlay was placed. The mixture type is CMHB-F. This project is therefore similar to a two layers AR system composed of an AR interlayer and AR hot mix. The reflective cracking started to appear about a year ago. This project did not show any reflective cracking in the first 5 years. According to local DOT personnel, on a typical non-AR hot mix project in this section of IH-20, reflective cracking start to show up in 3 to 6 months after placement. Therefore reflective cracking resistance of this two-layer AR system far exceeds that of conventional hot mix. Pavement surface has good texture and skid resistance. There is some evidence of slight rutting in left wheel path of outside lane.

PaveTex Engineering and Testing, Inc. Odessa, Ector County, IH 20-2

PaveTex Engineering and Testing, Inc. Odessa, Crane County, SH 385-1

Highway: SH 385 County: Crane District: Odessa Project: STP 97(291)R CSJ: 0600-03-016 Project limits: Starts South of Crane city limits goes North to Crane County Line Project Rating: Excellent This is an Excellent Project, with excellent ride. There are no flaws in this project. The project is composed of over 140,000 tons of AR hot mix. Hot mix type is CMHB-F, This project has received NAPA’s Quality award.

PaveTex Engineering and Testing, Inc. Odessa, Crane County, SH 385-2

PaveTex Engineering and Testing, Inc. Abilene IH 20-1

Highway: IH 20 County: Nolan District: Abilene Project: CPM 6-2-91 CSJ: Project limits: From Sweetwater to West of Roscoe ( 9.3 Miles Eastbound Lanes Only) Project Rating: Excellent The project is currently one year old with satisfactory performance and no reflective cracking. This Asphalt Rubber Hot Mix project has CMHB-F gradation. The project is in excellent condition and has good ride. There is no reflective cracking after one year of service

PaveTex Engineering and Testing, Inc. Abilene IH 20-2

AR surface texture

Appendix B

Porous Friction Course (PFC) Projects

Table 3. Porous Friction Course Asphalt Rubber Projects


94 Odessa Midland IH 20 11,200 IM 20-1(124)154 0005-03-054

IH-20 loop around Stanton. From Intersection of BI-20 West of town to 1 mile East of intersection of BI-20 East of town.

95 Odessa Martin IH 20 11,100 IM 20-1( 129 ) 158 0005-04-055

From end of CSJ 005-04-0054 to Howard County line

95 Lufkin Polk SH 146 8,300 STP 95(85)HEC,etc 0388-01-035,etc

South of Livingston. From Intersection of US 190 South to FM 1988

2000 Odessa Ward IH 20 5,900 0004-04-073From E of Monahans W to Pyote. First half

2000 Odessa Ward IH 20 5,700 0004-04-075From E of Monahans W to Pyote. second half

PaveTex Engineering and Testing, Inc. Odessa, Midland County, IH 20- 1

Highway: IH-20 County: Midland District: Odessa Project: IM 20(1(124)154 CSJ: 0005-04-054 Project limits: Exit 154 about 1 Mile West of Intersection of BI-20 E. to about 1Mile past intersection of BI-20 Project Rating: Excellent Slight amount of reflective cracking in passing lane where overlay was placed over existing ACP. No cracking in driving lane where full depth rehabilitation was performed. Project was built in 1994. The project consisted of milling the driving lane and filling it with conventional hot mix. The entire pavement was then overlaid with AR Porous Friction Course. Reflective cracking in passing lane at 40 feet spacing. This is the lane that was not milled and filled. The driving lane has no reflective cracking. Excellent ride after 6 years of service. This project was placed in late fall, there were some problems with mix getting cold and clumping together, so trucks had to be trapped.

PaveTex Engineering and Testing, Inc. Odessa, Martin County, IH-20- 1

Highway: IH-20 County: Martin District: Odessa Project: IM 20-1(129)158 CSJ: 0005-04-055 Project limits: Near Loop 214 E. of Stanton to Howard Co. line Project Rating: Excellent Slight amounts of reflective cracking Project was built in 1995. This project covers the existing hot mix pavement with AR seal coat ( Interlayer) and overlaying the pavement with AR Porous Friction Course. Reflective cracking is beginning to appear infrequently specially in fill areas. In no-fill areas there are very few reflective cracks. Excellent ride. The appearance of this 5 year old project is like a new project.

PaveTex Engineering and Testing, Inc. Odessa, Martin County, IH-20- 2

PaveTex Engineering and Testing, Inc. Lufkin, SH 146-1

Highway: SH 146 County: Polk District: Lufkin Project: STP 95(85)HEC, etc CSJ: 0388-01-035, etc Project limits: From US 190 intersection S. to FM 1988 about 4.5 miles Project Rating: Good Reflective cracking on South end of the project, near FM 1988, rest of the project is in Excellent condition. This is a Porous Friction Course (PFC) where Asphalt Rubber was utilized for binder. The project is located on SH 146 South of city of Livingston. The PFC was placed directly over a severely cracked hot mix pavement. Extent of cracking in the existing pavement is evident on the shoulders where PFC was not placed. The overall condition of the PFC is excellent. On the North end of the job cracks have not reflected through. Cracks are evident in the shoulder, but don’t penetrate through the PFC as shown in the picture below. This project was visited during a light rain. In the sag of vertical curves water is accumulating on the pavement. Also, in some locations water spray behind trucks is evident, indicating some of the voids have been filled. In the South ½ mile of the project, from Langham Road to FM 1988, majorities of cracks have reflected through as shown in the picture. Reflective cracking appear to be mostly limited to this ½ mile section. The area engineer states that crumb rubber was removed from the binder in this section to provide a control section to evaluate effectiveness of asphalt rubber. Based on this comparison, it is evident that the section with crumb rubber has far outperformed the section without the rubber.


Overview of the project


Cracks have not reflected through in most of the project, Note cracks in existing pavement on the shoulder

Cracks under PFC


Cracking in the South ½ mile of the project has reflected through PFC. This is the control section without crumb rubber


Extent of back spray behind a truck

No back spray behind cars.

PaveTex Engineering and Testing, Inc. Odessa Ward Co Jobs-1

Highway: IH-20 County: Ward District: Odessa Project: CSJ: 0004-04-073 & 0004-04-075 Project limits: From E. of Monahans W. to Pyote Project Rating: Excellent This Open Graded Friction Course was constructed in Spring of 2000. The surface is extremely uniform, excellent ride, excellent appearance, no distresses or any flaws in the entire project.

PaveTex Engineering and Testing, Inc. Odessa Ward Co Jobs-2

Appendix C

Seal Coat Projects

Table 4. Asphalt Rubber Seal Coat Projects


92 Bryan Madison FM 247 1,250 CPM-475-3-44,etc 0475-03-044,etc

From Midway on FM 247 about 9.5 miles south to Bedios creek. One section on IH 45, about 2 miles south and 2 miles North of SH 21. This section may be SAMI (CSJ 0645-05-034)

92 Bryan Madison OSR, etc 470 CPM-475-3-44,etc 0475-03-044,etc

There are 9 different locations. Main locations on OSR From IH 45 to Midway about 14 miles. One section on IH 45, about 2 miles south and 2 miles North of SH 21. This section may be SAMI (CSJ 0645-05-034)

96 Childress Donely US 287 7,200 NH 96(11)R,etc 0042-07-045, etcUS 287 South Bound, From Clarendon to Hedly

89 El Paso Presidio US 90 770 Between Alpine and Marfa

95 El Paso Culberson IH 10 9,000Between Van Horn and IH 10/ IH 20 split

96 El Paso El Paso SH 20,etc 3,300 CPM2-3-16 etc 002-03-016, etc From Fabens S for about 12 miles96 El Paso El Paso FM 76 17,800 674-01-xxx From Loop 375 to FM 1109

2000 El Paso Culberson SH 54 210From Van Horn North to Guadalupe Mountain

95 Odessa Crane US 385 1,800 Between Crane and McCamey87 San Antonio Medina SH 173 1,350 0421-02-xxx Devine, From IH 35 S for 5 miles

88 San Antonio Bexar FM 1604 15,800

From SH 151 to US 90, AR chip seal is in turn lane, Info from S. Cox

91 San Antonio Bexar SP 536 12,300 CPM 17-1-31 0017-11-031 North of Bank Street

96 Wichita Falls Montague US 287 13,200 CSR 224-3-49 0224-03-49

US 287 from FM1125 just S. of Bowie North to Montague/ Clay Co. line

93 Amarillo Potter FM 1061 1,600 SMERP 4800-00-011 SMERP 4800-00-0110.75 mile E of FM 2381 to 2 mile E.

93 Odessa Ector FM 181 1,650 SMERP 4800-00-012 SMERP 4800-00-012Andrews Co. Line to 5.5 Miles N of SH 158

93 Odessa Martin SH 349 1,800 SMERP 4800-00-013 SMERP 4800-00-013Near FM 87 to Dawson Co. Line, Ref Marker 300 to 302, 48F06H

93 Brownwood Brown US 67 3,900 SMERP 4800-00-013 SMERP 4800-00-013Blanket Creek Bridge to 1.0 Mile N.

93 Brownwood McCullouch US 377 2,100 SMERP 4800-00-013 SMERP 4800-00-0131.0 Mile N. of FM 2996 S. to FM 2996

PaveTex Engineering and Testing, Inc. Bryan, FM 247-1

Highway: FM 247 County: Madison District: Bryan Project: CPM-475-3-44,etc CSJ: 0475-03-044,etc Project limits: From the town of Midway South for about 9.5 miles to Bedios Creek Project Rating: Excellent Slight longitudinal cracking and slight raveling, both intermittently. Grade 3, un precoated chips were used in this project. On the South side of the project, between Bedias Creek and FM 1428 there is no cracking, no bleeding. There is some ravelling between the wheel path and on centerline in this section. On the section North of FM 1428, there are some cracks. These cracks are not reflective cracks, the crack pattern indicate that carcks maybe due to faulting in the raod way. Other than the minor ravelling in non-traficked areas, the project is in excellent condition.

PaveTex Engineering and Testing, Inc. Bryan, FM 247-2

Crack pattern indicating faulting of the roadway, also note raveling.

Raveling between wheel path.

.

PaveTex Engineering and Testing, Inc. Bryan, OSR-1

Highway: OSR County: Madison District: Bryan Project: CPM-475-3-44,etc CSJ: 0475-03-044,etc Project limits: From SH 21 to about 4 miles N. to FM 1119 Project Rating: Excellent There are some wide cracks and failures caused by base shrinkage, the AR seal coat is excellent. Grade 3 un precoated chips were used in this project. There are frequent spot seal coats on this project. The spot seals cover the entire roadway, indicatin severe base failures. There are very wide and very deep cracks in this project. The cracks are more than 10 inches deep and more than 1 inch wide as shown in the pictures. These cracks are likely shrinkage cracks caused by long period of severe draught in Texas. Several of the spot seals have also cracked. The majority of these deep cracks are in the first 5 miles of the project. The AR seal coat has performed in an excellent manner for its intended purpose.


Wide, deep cracks.


Cracks are more than 10 inches deep.

Spot Seals

PaveTex Engineering and Testing, Inc. Childress, US 287- F-1

Highway: US 287 County: Donely District: Childress Project: NH 96(11)R, etc CSJ: 0042-07-045,etc Project limits: US 287 Southbound lanes, from Clarendon to Hedly Project Rating: Excellent No Cracking or Bleeding This is a 4 years old Grade 3 seal coat with light weight rock. Crack pattern from underlying pavement is evident from crack shadows, but cracks have not reflected through the AR crack seal. There is some darkening of seal coat in the wheel path, but there is no bleeding. This is an excellent seal coat project


The crack pattern from underlying pavement is evident from the crack shadows, but cracks have not reflected through the AR seal coat.

Close examination of crack shadows shows that cracks have not reflected through the AR seal coat.

PaveTex Engineering and Testing, Inc. El Paso, Presidio County, US 90 -1

Highway: US 90 County: Presidio District: El Paso Project: ?? CSJ: ?? Project limits: Between Alpine and Marfa AR seal coat was placed about 1989. The main lanes were seal coated again at a later date. The original AR seal coat remains on the shoulders. They’re no cracking on either the shoulder or main lanes. This picture shows the crack in the pavement under the AR seal coat. The crack has not reflected through AR seal coat even after more than 10 years.

PaveTex Engineering and Testing, Inc. El Paso, Presidio County, US 90 -2

PaveTex Engineering and Testing, Inc. El Paso, Culberson County, IH 10-1

Highway: IH-10 County: Culberson District: El Paso Project: CSJ: 0003-01-044 & 0003-03-036 & 0003-04-042 Project limits: From IH 20/ IH 10 split to city of Van Horn Project Rating: Excellent Slight bleeding in isolated spots, moderatee edge cracking and patching. This section of IH-10 in Culberson County between where IH-10 and IH-20 split has a long history of AR seal coat. The original pavement surface is Portland Cement Concrete. In 1993 a two layer AR surface treatment was placed in this project (CSJ 003-02-032). In 1995 a grade 3 AR seal coat was placed. This seal coat is still in service after 5 years. There is no evidence of chip loss and chip embedment is good. The wheel path in both driving and passing lanes look dark, but there is no evidence of bleeding or loss of friction except is few isolated areas in the project. There is no transverse cracks evident, showing great resistance to reflective cracking. There is some isolated longitudinal edge cracks along the edge of driving lane. In some areas these longitudinal cracks have resulted in water pumping from under concrete slabs and result in loss of base under concrete and cause concrete failures. These failed areas have been patched as shown in the last picture.


Isolated Patches at the edge of concreteslabs, show concrete failures

PaveTex Engineering and Testing, Inc. El Paso FM 76-F-1

Highway: FM 76 County: El Paso District: El Paso Project: CSJ: 674-01-xxx Project limits: From Loop 375 to FM 1109 Project Rating: As a Seal Coat :Poor As an Interlayer : Good Severe reflective cracking in seal coat This AR seal coat was reportedly placed in 1996. The intersections have been overlaid with hot mix and they don’t show any reflective cracking. Therefore, the AR seal coat is acting as an effective interlayer to prevent reflective cracking. The sections between intersections are still exposed to traffic and they exhibit severe block cracking and fatigue cracking in wheel path. Therefore the performance of seal coat in preventing these cracks from reflecting is poor. There is no evidence of bleeding in this job.

PaveTex Engineering and Testing, Inc. El Paso SH 20-F-1

Highway: SH 20 County: El Paso District: El Paso Project: CPM 2-3-16 etc CSJ: 002-03-016,etc Project limits: From Fabens S. for about 12 miles Project Rating: West End of project, Poor East End of project, Fair Frequent Bleeding On the West end of the project S. Of Fabens there is severe bleeding. Bleeding is continuos in both directions and in all wheel paths. Crack pattern from underlying pavement is evident by shadows, but cracks have not reflected through the AR seal coat. On the East end of the project, just E. of Tornillo bleeding becomes less severe and severity decreases more as we approach the Eastern edge of the project. There is evidence that AR shot rate was decreasing as project progressed from West to East. Even in the Eastern edge of the project with lower AR shot rates and much less bleeding, cracks have not reflected through the AR seal coat. This indicates that perhaps the reflective cracking resistance of AR may be attainable at lower AR shot rates than those commonly used.

PaveTex Engineering and Testing, Inc. El Paso SH 20-F-2

Bleeding in West end of the job

Bleeding in East end of the job, just East of Tornillo is much less severe than East end. Evidence that AR shot rate may have been reduced.

PaveTex Engineering and Testing, Inc. El Paso SH 54A-1

Highway: SH 54 County: Culberson District: El Paso Project: CSJ: ?? Project limits: From Van Horn N. to Gualdalupe Mountain This project was inspected during construction. The section which was just paved inside Van Horn City limits was exhibiting bleeding with normal shot rates of about 0.45 to 0.5 gal/ Sq yd. The pre coated chips were extremely flat and elongated and they were sinking into the AR binder. To alleviate the problem AR shot rate was reduced to 0.38 to 0.4 and the bleeding appeared to stop at those shot rates.

Section at 0.38 Gal/ Sq Yd shot rate.

PaveTex Engineering and Testing, Inc. Odessa SH 385-F-1

Highway: SH 385 County: Crane District: Odessa Project: CSJ: ??? Project limits: Between Crane and McCamey Project Rating: Excellent This seal coat was placed over a new hot mix project which was exhibiting water permeability. Water penetration through the hot mix layer had caused some premature failure of granular base. All failures were repaired prior to AR seal coat. The aggregate is a Grade 4 aggregate. There is minor raveling of chips in the centerline. There are a few isolated patches associate with base failure. There are no distresses associated with the seal coat.

PaveTex Engineering and Testing, Inc. San Antonio, Bexar Co., FM 1604-1

Highway: FM 1604 County: Bexar District: San Antonio Project: ? CSJ: 2452-1-? Project limits: From SH 151 to US 90 Project Rating: Excellent Grade 3 un- precoated Trap rock and Limestone blend Grade 3 chips used in this project are a blend of Trap Rock and Limestone. Portions of this project at the intersections has been reconstructed to add a turn lane. The segments between intersection is AR seal coat. The performance of this seal coat project is excellent. There are no evidence of cracking, chip loss or bleeding in this heavily travelled roadway.

PaveTex Engineering and Testing, Inc. San Antonio, Bexar Co., SP536-1

Highway: SP536 County: Bexar District: San Antonio Project: CPM 17-1-31 CSJ: 0017-11-031 Project limits: SP 536 ( Probandt Street) from Bank Street North Project Rating: Excellent Grade 3 un- precoated Trap rock and Limestone blend Grade 3 chips used in this project are a blend of Trap Rock and Limestone. Probandt street is a heavily travelled city street near San Antonio stockyard. The traffic is mostly commercial truck traffic. The seal coat is in excellent condition. There are no signs of bleeding. There is moderate amounts of reflection cracking. Most cracks are transverse with intermittent longitudinal cracks.

PaveTex Engineering and Testing, Inc. San Antonio, Bexar Co., SP536-2

Typical Cracking Pattern

PaveTex Engineering and Testing, Inc. San Antonio, Medina Co., SH 173-1

Highway: SH 173 County: Medina District: San Antonio Project: ? CSJ: 0421-02-??? Project limits: Near Devine, Texas. From IH 35 South about 5 Miles ADT: Project Rating: Excellent Grade 3 un- precoated Trap rock and Limestone blend Grade 3 chips used in this project are on the fine side of the grading band. There is some bleeding at the intersection with IH 35 where there is heavy turning traffic. There is no bleeding in the South bound lane. Some bleeding in isolated spots in the North bound lane. There are no signs of cracking or ravelling in this project. Southern end of the project

PaveTex Engineering and Testing, Inc. San Antonio, Medina Co., SH 173-2

Typical Section

Bleeding in isolated locations, North bound.

PaveTex Engineering and Testing, Inc. Wichita Falls, US 287-F-1

Highway: US 287 County: Montague District: Wichita Falls Project: CSR 224-3-49 CSJ: 0224-03-49 Project limits: From FM 1125 just S. of Bowie N. to Mantague/ Clay Co. Line Project Rating: Good Good chip Retention, Slight Bleeding The southern ½ of this AR seal coat project has been overlaid with HMAC, therefore the original seal coat in the southern portion is acting as an Interlayer. In the South section ( with overlay), reflective cracking is evident at 150 feet spacing. Reflective cracks are mainly in driving lane. This section of US 287, the original pavement was PCC with crack spacing about 30 feet. Reflective crack spacing of 150 feet indicates that 1/5 of the cracks have reflected through the AR seal coat and over lay. In the Northern section of this project, AR seal coat is still exposed to traffic ( No overlay). Crack spacing in underlying pavement is evident by crack shadows and the spacing is about 30 feet, however, the crack spacing in AR seal coat is 150 feet. This indicates that only 1/5 of the cracks have reflected through the AR seal coat. Good rock retention . Wheel paths have darkened but there is no bleeding which can interfere with skid resistance. AR Seal Coat under HMAC Overlay


AR Seal Coat

PaveTex Engineering and Testing, Inc. Amarillo, Potter Co. FM 1061-1

Highway: FM 1061 County: Potter District: Amarillo Project: SMERP 4800-00-011 CSJ: SMERP 4800-00-011 Project limits: 0.75 Miles E. of FM 2381 to 2 Miles E. Project Rating: Good All sections have cracked, but AR seal coat section has least number of cracks. This is one of the SMERP (Supplemental Maintenance Effectiveness Research Program) test sections that were placed in 1993. The SMERP project consisted of placing several maintenance strategies on the same roadway section using the same contractor and the same aggregates. Each section consisted of AR seal coat, Emulsion seal coat, Polymer modified seal coat, Microsurfacing, Fog seal and a control section with out any treatment. AR Seal Coat: Shows slight bleeding, but not to the extent of causing skid problems. Seal coat rock is Grade 4, mostly uncrushed. Cracks pattern in the underlying pavement is visible through shadows, but most cracks have not reflected through. The ones that have reflected through appear to be healing in the wheel path. Latex and Emulsion Seal coat Sections: These sections have cracking. Cracks are wide and numerous. There are longitudinal as well as transverse cracks. Did not find fog seal or control in this project.


AR Seal Coat

Cracks healing in the wheel path in AR section.

PaveTex Engineering and Testing, Inc. Odessa, Ector County, FM 181-1

Highway: SH-181 County: Ector District: Odessa Project: SMERP 4800-00-012 CSJ: SMERP 4800-00-012 Project limits: From Andrews Co. Line to 5.5 Miles N. of SH 158 Project Rating: Excellent This is one of the SMERP (Supplemental Maintenance Effectiveness Research Program) test sections that were placed in 1993. The SMERP project consisted of placing several maintenance strategies on the same roadway section using the same contractor and the same aggregates. Each section consisted of AR seal coat, Emulsion seal coat, Polymer modified seal coat, Microsurfacing, Fog seal and a control section with out any treatment. In this project the AR seal coat looked great, but all the other treatments also looked great, with exception of Fog seal and control. These two sections were worse than all other treatments. The Microsurfacing section is the only section that showed cracking. The cracking in Microsurfacing was mostly edge cracking. All different types of seal coat looked about the same.

PaveTex Engineering and Testing, Inc. Odessa, Ector County, FM 181-2

Control Section

AR Seal Coat

PaveTex Engineering and Testing, Inc. Odessa, Martin County, SH 349-1

Highway: SH-349 County: Martin District: Odessa Project: SMERP 4800-00-013 CSJ: SMERP 4800-00-013 Project limits: From Near FM 87 to Dawson Co. Line, Reference Marker 300 to 302 Project Rating: Good This is one of the SMERP (Supplemental Maintenance Effectiveness Research Program) test sections that were placed in 1993. The SMERP project consisted of placing several maintenance strategies on the same roadway section using the same contractor and the same aggregates. Each section consisted of AR seal coat, Emulsion seal coat, Polymer modified seal coat, Microsurfacing, Fog seal and a control section with out any treatment. Asphalt Rubber Seal Coat Section: Reflective cracking, 30-40 feet spacing Polymer Modified Seal Coat Section: Reflective cracking 30-40 feet spacing, some chip loss, pumping from some of the cracks and flushing in isolated areas. Latex Modified Seal Coat Section: About the same as AR section, with slight flushing in isolated area Emulsion Seal Coat Section: About the same as AR section, with slight flushing in isolated area Fog Seal Section: Numerous patches, cracks have deteriorated and beginning to alligator Control Section: Same as fog seal section Asphalt Rubber Section


Asphalt Rubber Surface Texture

Microsurfacing Section


Polymer Modified Section

Latex Section


Fog Seal

Control Section

PaveTex Engineering and Testing, Inc. Brownwood , Brown County, US 67-1

Highway: US 67 County: Brown District: Brownwood Project: SMERP 4800-00-011 CSJ: SMERP 4800-00-011 Project limits: Blanket Creek to 1.0 Mile North Project Rating: Good All sections have cracked, but AR seal coat section has least number of cracks. This is one of the SMERP (Supplemental Maintenance Effectiveness Research Program) test sections that were placed in 1993. The SMERP project consisted of placing several maintenance strategies on the same roadway section using the same contractor and the same aggregates. Each section consisted of AR seal coat, Emulsion seal coat, Polymer modified seal coat, Microsurfacing, Fog seal and a control section with out any treatment. Grade 4 lightweight non-precoated chips were used in all test sections in McCullough County. All the four seal coat sections (AR, Polymer, Latex and AC) performed well with respect to resistance to cracking. Transverse cracks in the AC section were wider than the rest. Asphalt Rubber section is shown more flushing than the rest.

PaveTex Engineering and Testing, Inc. Brownwood , Brown County, US 67-2

AR Seal Coat: There is flushing in this section, with minor amounts of cracking.

Polymer Seal Coat Section: This section is bleeding the same as the hot rubber seal coat section. There is slightly more cracking in this section than the AR section. Latex Seal Coat Section: There is less flushing in this section than the AR or Polymer sections, but there is also more cracking and some raveling. AC Seal Section about the same amount of flushing as Polymer or AR section. The cracks in this section are wider than the other three sections. Fog Seal Section: Picture below shows extent of cracking in fog seal section, which would be about the same as control. There was no control section in this project.

PaveTex Engineering and Testing, Inc. Brownwood , McCullough County, US 377-1

Highway: US 377 County: McCullough District: Brownwood Project: SMERP 4800-00-011 CSJ: SMERP 4800-00-011 Project limits: 1.0 Mile North of FM 2996 South to FM 2996 Project Rating: Good All sections have cracked, but AR seal coat section has least number of cracks. This is one of the SMERP (Supplemental Maintenance Effectiveness Research Program) test sections that were placed in 1993. The SMERP project consisted of placing several maintenance strategies on the same roadway section using the same contractor and the same aggregates. Each section consisted of AR seal coat, Emulsion seal coat, Polymer modified seal coat, Microsurfacing, Fog seal and a control section with out any treatment. Grade 4 lightweight non- precoated chips were used in all test sections in McCullough County.


AR Seal Coat : This section looks good without any bleeding. There is one longitudinal crack in this section and one fresh patch near a driveway.

Picture below in AR Section, shows cracks in the shoulder that was not seal coated, but no cracks in AR seal coat section.


Picture below shows the cracks in the Shoulder. These cracks stop where AR seal coat starts

Polymer Seal Coat Section: This section is bleeding more than asphalt rubber section. Resistance to cracking is the same as asphalt rubber section.


Latex Seal Coat Section: This section has more cracking than AR or Polymer. It has less bleeding than the Polymer section.

AC Seal Section: This section has more flushing than AR, Polymer or Latex sections. The cracks in this section are also wider than those already mentioned.


Picture below shows the cracks in AC section. These cracks are wider than the ones in AR, Polymer or Latex sections.

Fog Seal Section: This section much Transverse and longitudinal cracks, also some bleeding.


Control Section: Looks about the same as fog seal. Much transverse and longitudinal cracks.

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