Investigation into the Use of Reclaimed Asphalt Pavement in Gap- and Open-Graded Asphalt Rubber Mixes: Phase 2: Laboratory Testing of Aggregate Replacement and CalME Simulation

This report presents data and analysis completed to evaluate changes in mix properties and simulated mix performance in pavement structures when using coarse reclaimed asphalt pavement (RAP) materials in new gap- and open-graded rubberized hot mix asphalt (HMA) (structural performance for gap-graded mixes only) and to prepare recommendations and suggested specification language, if considered appropriate, for allowing the use of coarse RAP in gap- and open-graded rubberized hot mix asphalt. This report includes laboratory binder and mix testing, as well as CalME fatigue and reflective cracking simulation results for four plant-produced gap-graded rubberized hot mix asphalt (RHMA-G) mixes used on the Heavy Vehicle Simulator test track at the UCPRC. The four mixes had the same base binder and two aggregate gradations, both with and without RAP. Six laboratory-produced mixes were also tested, using rubberized binders from two field projects and two RAP sources. Three mixes were produced with each base asphalt rubber binder—one with no RAP and two with 10% RAP by dry weight of aggregate from each of the two RAP sources. Testing of all mixes included stiffness frequency sweeps, flexural fatigue, rutting, and moisture sensitivity. Binder testing was performed on binder extracted from the test track mixes. Four open-graded rubberized hot mix asphalt (RHMA-O) mixes were also tested in this study for draindown and mechanical durability. Pavement fatigue and reflective cracking performance were simulated using the CalME mechanistic-empirical software and the flexural stiffness and fatigue laboratory test results. Simulations included all the different plant-produced and laboratory-produced RHMA-G mixes. The simulations addressed questions regarding the effect of adding 10% RAP to the mixes, the effects of maximum aggregate size gradation, the effects of different RAP sources, the effects of different asphalt rubber binders, the effects of different ratios of RHMA to HMA in new asphalt layers, and the effects of using full-depth RHMA compared to using an RHMA surface on new HMA in new asphalt layers. Simulations included new or reconstructed pavement, asphalt overlays on cracked asphalt pavement, and asphalt overlays on cracked concrete pavement.