Laboratory Study on Effects of High Reclaimed Asphalt Pavement and Binder Content: Stiffness, Fatigue Resistance, and Rutting Resistance

The objective of this study was to improve the performance of asphalt concrete mixes containing reclaimed asphalt pavement (RAP) by evaluating the optimal binder content depending on the percentage of RAP in the mix. Mixes with three percentages of RAP (0%, 20%, and 40%) obtained from an asphalt producer and three percentages of added asphalt binder (design asphalt content, design 10.5%, and design 11.0%) were evaluated. A laboratory mix containing 100% RAP with three additional levels of asphalt binder content (0.0%, 0.5%, 1.0%, and 1.5%) was also evaluated to determine the additional binder level that optimizes mix performance. Performance of the mixtures was evaluated on the basis of three criteria: stiffness (dynamic modulus), fatigue resistance, and rutting resistance (flow number). That aged RAP binder in high-RAP mixes aids stiffness and rutting resistance is well established, but the binder poses problems for fatigue resistance. Results showed that a 0.5% increase in binder content improved both fatigue and rutting resistance of the 0% and 20% RAP mixes, with only slight decreases in dynamic modulus. The addition of various amounts of binder to the 40% RAP mix led to a decrease in both rutting and fatigue resistance; this decrease suggests that the plant-produced mix already incorporated the optimum asphalt content in the original design. The mixes containing 100% RAP exhibited extremely high dynamic modulus and rutting resistance at all binder levels tested, and fatigue resistance comparable to the 20% RAP mix was achieved for the mix with the addition of 1.5% binder.