Low-temperature cracking and aging performance of modified asphalt concrete specimens

The thermal stress restrained specimen test (TSRST) was used to evaluate the low-temperature cracking resistance and aging performance of modified asphalt concrete (AC) specimens. One aggregate, two asphalt cements (AAA-1 and AAB-1), five modifiers (latex polymer, ethylene acrylate copolymer, rubber powder, elastomer, and a blend of polypropylene and Kevlar fibers), and four 85 degrees C oven aging levels (0, 5, 25, and 50 days) were considered. The results of the bending beam rheometer test (BBRT) on binders at -20 degrees C showed that AAA-1 displayed a smaller creep stiffness than AAB-1. Only two modifiers increased the deflection and softness of AAB-1. The additives in AAA-1 did not improve its low-temperature rheological behavior. These results served as the basis for comparison with those from the TSRST. The fracture strength and temperature of AC specimens are sensitive to asphalt type (4.11 MPa and -32.2 degrees C for AAA-1, 3.28 MPa and -25.4 degrees C for AAB-1) and degree of aging (from 4.11 to 2.04 MPa and from -32.2 to -21.2 degrees C for AAA-1 for aging levels from 0 to 50 days at 85 degrees C). Only one modifier in AAB-1 (among the two candidates identified with the BBRT) improved the low-temperature performance of the AC specimens. After 50 days of aging, no improvement was observed. The modified AAA-1 AC specimens displayed an optimum improvement in performance for aging levels of 25 and 50 days. Several modified AC specimens displayed a low-temperature failure without apparent fracture. This behavior would appear to he advantageous for the performance of pavements in cold regions.