Response behavior of asphalt mixtures at low temperatures under varying indirect tensile test loading conditions

This paper investigates the effect of loading level and loading rate on the damage development and strength of asphalt mixtures. Indirect tensile creep tests with different loading levels and strength tests with three loading rates were performed at three low temperatures for ten mixtures.An acoustic emission (AE) system with eight recording channels was used to monitor the development of micro cracking in the specimens for both tests for one mixture. The experimental results show that test temperature has a significant effect on the behavior of the material. Data analysis from the creep test indicates that the creep loading level significantly affects the response of the tested material. The AE rate analysis shows that no actual damage develops when a creep load is less than 20 % of the strength and significant micro damage accumulates when the applied creep load is more than 30 % of the strength value. The loading rate was found to have a significant effect on the measured tensile strength even at a relatively low temperature, and the measured tensile strength increases with the increase of the loading rate for all the test temperatures considered in this study. However, this effect was found to be diluted with the decrease of the test temperature. The AE analysis indicates that a damage zone develops in both the creep and strength tests. The damage zone decreases with temperature decrease and increases with the increase of the loading level applied during the creep test. The damage zone obtained from the strength test was approximately equal to that from the creep testing with a loading level about 25-50 % of the strength value.