Evaluating the effect of reclaimed asphalt pavement on rubberized hot mix asphalt in pilot projects

The study goal is to evaluate the use of up to 10 % reclaimed asphalt pavement (RAP) by aggregate replacement in rubberized hot mix asphalt-gap graded RHMA-G mixes to identify any significant potential problems for durability. Five pilot projects were built, each including a control RHMA-G (without RAP) and an RHMA-G with 10 % RAP. The mixes were sampled during production and evaluated using volumetric assessment, and performance related tests including stiffness, four-point bending fatigue resistance, fracture resistance measured with the IDEAL cracking test, and rutting resistance. Mix testing results indicate that the addition of 10 % RAP had minor effects on the mechanical properties. With a few exceptions related to the total binder content of the mixes, the effect of the RAP addition was negligible compared to normal production variability. Modeling with CalME, Caltrans mechanistic-empirical asphalt pavement design software and four-point bending testing results, indicated that RAP addition effects on pavement cracking performance were either negligible or comparable to mix-to-mix RHMA-G variability. Regarding constructability, RAP addition did not create any problems. The life cycle assessment completed in the study indicates that the addition of 10 % RAP to the RHMA-G can reduce the greenhouse gasses emissions associated with the RHMA-G production (cradle-to-gate) by up to 5 %.