Evaluating Recycling Agents’ Acceptance for Virginia: Test Protocols and Performance-Based Threshold Criteria

By 2013, the Virginia Department of Transportation (VDOT) had begun to consider the feasibility of allowing the use of surface mixtures containing up to 45% of recycled asphalt pavement (RAP) material. The primary concern has been that the use of high percentage of RAP will overly stiffen these mixtures; making them more brittle and prone to premature cracking. The challenges arising from the use of high RAP content mixtures can be addressed through the use of softer binders or additives such as recycling agents (RAs). Currently, there are no unique and / or detailed handy guides or specifications that outline a framework to evaluate acceptability of RAs in the Commonwealth of Virginia. Therefore, this study aims to identify and / or develop a testing protocol to evaluate the effectiveness of RAs in alleviating the brittleness of high RAP asphalt mixtures. In addition, performance-based parameter(s) with threshold limits / criteria will be identified or developed to accept or reject recycling agent products. Both objectives will facilitate responsible use of innovative materials as part of Virginia’s Balanced Mix Design initiative. The scope of work will include procuring asphalt binders, RAP material, and RAs from various sources and suppliers. Binder and mortar blends will be produced in the laboratory and will be subjected to a suite of rheology- and chemistry-related tests. High RAP asphalt mixtures containing RAs will be produced and will be subjected to a suite of tests including Cantabro mass loss test, Asphalt Pavement Analyzer rut test, IDEAL cracking test, dynamic modulus test, flow number test, stress sweep rutting test, and fatigue pull-pull test at various aging conditions. Finally, the performance of field trial sections previously constructed in the past two-four years using high RAP mixtures with RAs will be assessed. Available data from Virginia’s accelerated pavement testing program, which is expected to shortly include asphalt mixtures with high RAP and RAs, will be also considered.