Mechanistic-Empirical Simulations and Life-Cycle Cost Analysis to Determine the Cost and Performance Effectiveness of Asphalt Mixtures Containing Recycled Materials

Use of reclaimed asphalt pavements (RAP) and recycled asphalt shingles (RAS) in asphalt paving, although considered as sustainable, is a practice that agencies are reluctant to employ because of the unpredictability of asphalt mixes containing recycled materials. The asphalt binder in RAP/RAS is aged and stiffened, which reduces ductility of the pavement. Consequentially, a pavement can exhibit unsatisfactory fatigue performance and have the potential for early cracking failure. Although methods exist to counteract the brittle behavior of pavements containing RAP/RAS (namely binder-grade bumping, binder-grade dumping and high binder content), they are not accounted for in mechanistic-empirical (ME) pavement design. Additionally, the cost benefits of using RAP/RAS in pavements are not easily calculated. For these reasons, characterization of fatigue performance for asphalt pavements containing RAP/RAS in ME design software needs to be accomplished and a life-cycle cost analysis (LCCA) framework for pavements containing RAP/RAS needs to be developed so that agencies can make informed decisions about RAP/RAS use in asphalt mixtures. In this study, laboratory test results for asphalt mixtures with different combinations of RAP/RAS contents, binder contents, and binder types were used to calculate ME pavement model coefficients to perform forward calculations to determine pavement performance. Using predicted performance from ME models, LCCAs were conducted to determine the cost benefits of using binder-grade bumping/dumping and high binder content in Oregon asphalt mixtures. These strategies are expected to increase RAP/RAS use in asphalt mixtures, reduce life-cycle costs, improve the cracking performance and encourage widespread use of RAP/RAS asphalt mixtures.