University of California Pavement Research Center

Three pilot projects were constructed using hot mix asphalt (HMA) with higher percentages of recycled asphalt pavement (RAP) (25% to 40%) and recycled asphalt shingles (RAS) used at 0% or 3%. The three projects were paved between 2021 and 2022 on State Route 49 in El Dorado County (ED 49), State Route 215 in San Bernardino County (SBD 215), and State Route 26 in San Joaquin County (SJ 26). Two and a half to three years later, pavement condition surveys were conducted to observe surface distresses. On ED 49, the 3% RAS mix exhibited 6% low-severity wheelpath alligator cracking, often with mild pumping. The other mixes on ED 49 exhibited lower levels of alligator and total cracking. No alligator cracking was observed on SBD 215, which includes a cement-treated base not present in the other pilot projects. On SJ 26, all test sections exhibited some form of cracking, though mostly of low severity. Among the mixes, the 25% RAP/3% RAS mix showed the most alligator cracking on SJ 26 (around 7% of the wheelpath), while the 0% RAP/0% RAS control mix showed the most transverse cracking and the highest total cracking.