Fatigue and stiffness characteristics of asphalt mixtures made of recycled aggregates

This research studies the stiffness characteristics and fatigue life of several asphalt mixtures made of recycled glass, reclaimed asphalt pavement (RAP), and recycled concrete aggregate (RCA). Experiments were carried out at 5-35 degrees C, loading frequencies of 0.1-20 Hz, and at two microstrain levels of 200 and 400 mu m/m. To date, the effect of extensive parametric combinations of loadings, microstrain levels, and temperatures on asphalt mixtures made entirely of recycled materials (RM) has not been undertaken. The findings exhibited superior stiffness characteristics and improved fatigue life of some RM mixtures compared to control mixtures. The next step of this study included the optimization of three existing fatigue life prediction models. In addition, a prediction model was developed based on nominal maximum aggregate size (NMAS), percentage of RCA, and percentage of RAP in the asphalt mixture. The optimized models resulted in a much higher coefficient of determination (R2) and P -value (likelihood) in the statistical T-test compared to the existing prediction models utilized in this study. The developed model yielded R2 values close to 0.99 between measured and predicted fatigue life, indicating an enhanced accuracy in the prediction. Comparison of the estimated dissipation energy of mixtures supported and validated the fatigue testing outcomes.