Fracture Resistance of Rubber-modified Asphaltic Mixtures Exposed to High-Temperature Cyclic Aging

Abstract

The fracture resistance of rubber-modified asphaltic mixture exposed to different durations of high-temperature thermal cycling is investigated using the J-Integral approach. Crumb rubber content of 15%, as a percentage of the binder was adapted. Semicircular core specimens (76 mm radius and 57 mm thickness) were used for fracture resistance tests. A cyclic thermal aging program was performed in an environmental chamber between 20 and 50 C for four different periods (0, 8, 28, and 56 days). The effect of thermal cycling on the fracture resistance of the rubber-modified mixture, as determined by the critical energy release rate ( J1c), was studied and compared with samples of unmodified asphalt concrete mixture (0% rubber content). A relationship between the number of thermal cycles and the critical energy release rate was established. The current investigation revealed that the fracture resistance of the studied mixtures decreased as the number of thermal cycles increased. However, rubber modifier managed to improve the fracture resistance of the modified mixture over the entire range of the thermal cyclic program as compared to the unmodified mixture. The fracture resistance analysis of the studied mixture predicted from the J-integral concept is consistent with the prediction made based on the conventional indirect tensile strength test. Thus, fracture resistance can be correlated to indirect tensile strength. No significant improvement was found in the unconfined compressive strength of the modified mixture, when compared to the unmodified mixture when a rubber modifier was used at a higher number of thermal cycles.