Use of Recycled Asphalt Pavement in Rubberized Hot Mix Asphalt—Gap Graded

Current Caltrans Standard Specifications for rubberized hot mix asphalt–gap-graded (RHMA-G) do not allow the inclusion of reclaimed asphalt pavement (RAP). This report summarizes the research conducted by the UCPRC in support of the Caltrans-industry initiative “10% RAP in RHMA-G,” whose goal is to evaluate the use of up to 10% RAP (by aggregate replacement) in RHMA-G mixes, provided that the research does not identify significant potential problems for durability. Five pilot projects were built by Caltrans as part the initiative. In each of the pilots, a control RHMA-G (without RAP) and an RHMA-G with 10% RAP were placed. The mixes were sampled during production and tested using performance-related tests at the UCPRC laboratory. The results of the testing of the mixes—including stiffness, four-point bending fatigue resistance, and rutting resistance—indicate that the addition of 10% RAP had minor effects on the mechanical properties of the RHMA-G. With just a few exceptions related to changes in the total binder content of the mix, the effect of the RAP addition was negligible compared with project-to-project differences. Modeling with CalME software based on four-point bending testing results indicated that the impact of the RAP addition on the cracking performance of the pavement was either negligible or comparable to project-to-project differences. From the constructability point of view, the addition of the RAP did not create any problems. The life cycle assessment presented in this report 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%.