Annotated Literature Review for NCHRP Report 640 (2009)

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208 1.51.4 Construction Practices The first case study was conducted on SH 337, Palo Pinto County. Wimsatt and Scullion mention that this 17.7 km long roadway section consisted of (on average) 203 mm (eight inches) of granular base and two seal coats placed in 1970, followed by a seal coat placed in 1980, an open graded friction course placed in 1989, and another seal coat placed in 2000. The seal coats and open graded friction course together were approximately 51 mm (two inches) thick. However, before the last seal coat was placed, TxDOT maintenance personnel had applied many seal coat surface patches and asphalt patches on this roadway due to the disintegration of the open graded friction course. Wimsatt and Scullion indicate that in the second case study project (16.9 km long), US 377 Southbound Lanes, Hood County, the pavement was constructed in 1979 with 152 mm (six inches) of lime stabilized subgrade where clay subgrade was present, 254 mm (ten inches) of granular base and a 54 mm (two inch) asphalt surface. Asphalt level up courses and two open graded friction courses were then placed in 1988 and 1992, respectively. The total surfacing was approximately 178 mm (seven inches) thick. 1.51.5 Maintenance Practices As mentioned in the Construction Practices section, Wimsatt and Scullion indicate that it is the standard practice for TXDOT personnel to use seal coats over distressed OGFC section as part of their maintenance operations. 1.51.6 Rehabilitation Practices For both sections mentioned above, the authors mention that part of the rehabilitation option was to remove the overlay and the OGFC sections. For the SH 337 section, it was decided to repair the failed base areas and then put 75 mm of HMA. For the US 377 section, the plan was to apply 127 mm of HMA after the removal of the overlay and OGFC layers. 1.51.7 Performance The authors indicate that both sections, SH 337 and US 377, which had asphalt overlays on top of OGFC layers, were showing major distress. SH 337 was showing ruts up to 51 mm deep, and the section on US 377 was exhibiting substantial alligator cracking and potholes 1.51.8 Structural Design No information is provided on structural design of friction course. 1.51.9 Limitations No information is provided on limitations of use. 1.52 Cooper S. B., C. Abadie, and L. N. Mohammad. “Evaluation of Open- Graded Friction Course Mixture.” Louisiana Transportation Research Center Technical Assistance Report Number 04-1TA. October 2004.

209 1.52.1 General This report provides a history on the use of OGFC in Louisiana and documents the design of an OGFC project from 2003. Louisiana first developed and used OGFC in the late 1960’s and early 1970’s. The primary reason for using OGFC in Louisiana was to provide an improved skid resistant wearing surface. In 1973, the Louisiana Department of Transportation and Development issued an Engineering Directive to use OGFC on all roads with an average daily traffic (ADT) greater than 4,000. In 1980, the ADT limit was changed to all roads with ADT greater than 3,000. During the 1980’s, some problems were encountered with Louisiana’s OGFC pavements. At this time, many of the OGFC layers were 10 to 12 years old and had begun to fail. Failure was signaled by severe raveling in the wheel paths. Cooper et al stated that the severe raveling problems were related to moisture and temperature. The temperature problems were related to both mix temperature and weather. Moisture problems were related to the drying of aggregates during the production process and predominately associated with a particular aggregate type. To address these issues, a maximum moisture content for the aggregate, limiting OGFC construction to between May and September, and increasing ambient temperature requirements were implemented. Due to a number of factors, a second moratorium was placed on the use of OGFC in 1984. Just prior to the moratorium, experimental sections of OGFC were placed in which polymer modified asphalt binder were used. The experimental sections included a 4 mile section of OGFC containing a latex modified asphalt binder and 4 miles of OGFC containing an elastomeric polymer modified binder. Cooper et al state the latex modified binder was similar to a current PG 70-22 and the binder modified with the elastomer was similar to a PG 76-22. In addition to theses experimental sections, a control section was placed using an AC-30 asphalt binder. Within one year, this control section began raveling and within two years the wheel paths had completely raveled. Cooper et al stated that the experimental sections (using modified binders) were still performing in 1999 (15 years) when the entire project was rehabilitated. Based upon the success of these OGFC sections containing modified binders, Louisiana constructed a new OGFC test section in 2003. The remaining portion of the report deals with materials and mix design. 1.52.2 Benefits of Permeable Asphalt Mixtures The authors indicate that the high air void contents associated with OGFC promotes draining of rainwater from the pavement surface. This characteristic minimizes hydroplaning, reduces splash and spray and improves wet weather skid resistance. 1.52.3 Materials and Mix Design The authors provide discussion on a number of materials used for the 2003 project including: asphalt binder, aggregates, fibers, anti-strip additives and tack coat (for construction). The asphalt binder used for the project was polymer modified (elastomer) that was graded as a PG 76-22. Sandstone and limestone aggregates were used to

210 develop two aggregate gradations. No specifics were provided on the aggregates except that they met the applicable Louisiana specifications for OGFC. A mineral fiber in a pelletized form was added to minimize draindown potential. A fiber content of 0.1 percent by total mix mass was selected based upon laboratory draindown testing. The contractor did include a liquid anti-strip in the asphalt binder to minimize moisture susceptibility. A SS-1 emulsion was selected for the project and was applied at a rate of 0.07 g/yd2. The mix design was based upon the procedure recommended by the National Center for Asphalt Technology. Tables 103 and 104 present two aggregate blends that were evaluated as part of this mix design. Based upon the data shown in Tables 103 and 104as well as the results of Hamburg wheel tracking tests, Design 2 was selected and placed. 1.52.4 Construction Practices No specific construction practices were given. 1.52.5 Maintenance Practices No specific maintenance practices were given. 1.52.6 Rehabilitation Practices No specific rehabilitation practices were given. 1.52.7 Performance No specific performance measures were given. 1.52.8 Structural Design No specifics on inclusion within structural design were given. 1.52.9 Limitations No specific limitations were given.

211 Table 103: Composition of Mix Design Blends Percentage Material Design 1 Design 2 #78 Sandstone, FR I 84.0 67.2 #11 Sandstone, FR I 9.3 7.4 #89 Limestone, FR III 18.7 PG 76-22m 6.6 6.6 Fibers 0.1 0.1 Ad-Here LA 2 0.6 by Wt. of AC 0.6 by Wt. Of AC Table 104: Composite Blends and Mixture Properties Percent Passing Sieve Size Design 1 Design 2 QA Data LTRC 2nd Truck Required Gradation ¾” (19mm) 100 100 100 100 100 ½” (12.5mm) 90 92 93 91 85-100 3/8” (9.5mm) 58 64 68 66 55-75 No. 4 (4.75mm) 14 16 21 26 10-25 No. 8 (2.36mm) 9 8 11 18 5-10 No. 16 (1.18mm) 7 6 9 16 No. 30 (.600mm) 6 5 8 15 No. 50 (.300mm) 5 4 7 14 No. 100 (.150mm) 3.8 3.4 6 10 No. 200 (.075mm) 2.8 2.3 3.9 6.1 2-4 Gmb 1.916 2.173 Gmm 2.374 2.368 2.381 2.389 VCA 33.0 23.0 %Air Voids, AASHTO T166 19.3 8.2 18 Gsb 2.558 2.604 Gse 2.619 2.612 Pba 0.9 0.8 Pbe 5.9 6 Permeability, ft/day 276 453 Permeability, ft/day LTRC Results 235 278 Draindown 0.08 0.08 0.3 Design AC 6.6 6.6 7.0 6.8