UC Davis

In this study, a medium-term oven aging (MTOA) protocol of 20 h at 100 °C was applied to loose plant-produced mixes to evaluate the age-related and fatigue cracking resistance of asphalt mixes containing recycled materials. To evaluate the age-related cracking resistance, the indirect tensile IDEAL cracking tolerance test was performed on 27 plant-produced mixes, and fatigue cracking resistance was evaluated using the four-point bending (4PB) test on four selected mixes. MTOA resulted in an increase in strength and a reduction of the cracking tolerance index (CTIndex), while the fracture energy did not change much. Overall, the indirect tensile strength increased on average by 150 kPa (somewhat uniform shift for different mix types), and the CTIndex decreased by approximately 38% on average, indicating that the change in the CTIndex value depended on the short-term aged value. Based on 4PB test results, MTOA resulted in an increase of the dynamic modulus of the four mixes between 10% and 30% at 20 °C and 1 Hz, and a reduction of approximately 50% for the 4PB fatigue life for three out of the four mixes at strain levels of 400–700 µε, which are typical of thin overlays on cracked pavements. The fourth mix showed little effect of MTOA on 4PB fatigue life.