Implementation of New Quieter Pavement Research: Accelerated Pavement Testing and Laboratory Evaluation of Different Open-Graded Hot-Mix Asphalt Materials

This study presented in this report is part of a long-term effort that started in 2005 to develop the specifications, guidelines, standardized laboratory and field test methods, and other information needed for quieter pavement research to be incorporated into standard Caltrans practices, and lead to quieter pavements. Based on an earlier laboratory study, several open-graded friction course (OGFC) mixes were selected for further evaluation with accelerated pavement testing using the Heavy Vehicle Simulator (HVS) and laboratory testing on plant-produced materials. These selected mixes had shown good overall laboratory performance in terms of durability and sound absorption, which is correlated with tire/pavement noise. Specifically, the following HVS test cells were constructed for this experiment: Cell A: Caltrans 3/8 inch mix with PG 76-22PM binder, average as-built thickness = 0.06 ft. Cell B1: #4P mix with PG 76-22PM binder, average as-built thickness = 0.06 ft. Cell B2: Same mix as Cell B1, average as-built thickness = 0.07 ft. Cell C: #4P mix with PG 64-16 binder, average as-built thickness = 0.05 ft. Cell D: Georgia 1/2 inch mix with PG 58-34PM, average as-built thickness = 0.15 ft The #4P mixes had nominal maximum aggregate size of 4.75 mm (#4 sieve) with “P” indicating a coarser aggregate gradation identified in the earlier laboratory study. The five test cells included three new OGFC mixes, with the Caltrans 3/8 inch mix serving as the control mix. The study examined the performance of the selected OGFC mixes in terms of their constructability, rutting performance, moisture damage susceptibility, surface texture, permeability, clogging susceptibility, clogging and rutting mechanisms, and tire/pavement noise. Recommendations are made regarding further work with the #4 mixes, and temperatures for OGFC construction. While all of the mixes are feasible for a given project, the preliminary indications with regard to differences in expected performance are: The #4P mixes offer superior noise and mechanical durability compared with the control mix. They have similar skid resistance as measured by Caltrans Test 342 (CST) and surface permeability. They have lower macrotexture than the control, but more than dense-graded mixes. A rubberized binder may improve moisture sensitivity and rutting performance, which were better or worse than the control mix depending on the binder type. The Georgia 1/2 inch mix is likely to provide superior skid resistance and rutting performance compared to the control mix, although it could not be fully investigated in this project due to difficulties in getting it produced by local plants as designed. This mix is also likely to cost more because of the lime treatment and fibers recommended by the Georgia DOT in addition to the polymer-modified binder. Based on the results from this study, it is recommended that several pilot sections be placed using a rubberized binder. For these mixes to be placed, the gradations may need to be adjusted somewhat to be producible using current crushed stone bin gradations. Consideration should be given to increasing the minimum surface and air temperatures for paving of open-graded mixes.