Alternative Methodology for Assessing Cracking Resistance of Hot Mix Asphalt Mixtures with Overlay Tester

Abstract

Several highway agencies have either implemented or considered implementing performance tests to predict the cracking potential of asphalt concrete (AC) mixes in the laboratory setting. One such test, the overlay tester (OT), simulates the opening and closing of cracks induced by daily temperature variations and tensile strain generated by traffic loads. The variability of the OT results is expressed as a major concern in reliably characterizing cracking potential of AC mixes. A more fundamental analysis process and more mechanistic performance indicators were implemented that consider the two stages of the cracking mechanism (i.e., crack initiation and crack propagation). The repeatability of the proposed performance indices, critical fracture energy and crack progression rate, seems to be better than the current criterion based on the number of cycles to dissipate 93% of the initial maximum peak load. The proposed cracking methodology and associated preliminary failure limits seem to characterize and satisfactorily discriminate the cracking resistance of AC mixes. Given its promise in this study, the proposed OT test method is recommended as a routine test during the mix design process of AC mixes to predict and screen their cracking susceptibility.