Single-Event Cracking Temperature of Asphalt Pavements Directly from Bending Beam Rheometer Data

Asphalt pavements under low temperature conditions develop transverse cracks as a result of one or a combination of three distress mechanisms: (1) single-event thermal cracking; (2) thermal fatigue; and (3) load-associated thermal cracking. The cracking temperature of asphalt pavements based on the single-event thermal cracking mechanism of the asphalt binder has been suggested as a good measure of the low temperature criterion for use as a binder purchase specification. The determination of the single-event cracking temperature Tcr requires a comparison of the pavement thermal stress computed from the binder stiffness data generated from the bending beam rheometer (BBR) with the binder strength data measured using the direct tension test (DTT). Thus, two instruments, each with different sample preparation techniques, different sample sizes, and different data analysis methods, are required for the final determination of a single point signifying the cracking temperature. The present work revisits the method of data analysis to determine Tcr and shows that the cracking temperature can be obtained directly from the BBR data without the use of the DTT. The procedure uses the pavement thermal stress computed from the BBR binder stiffness data to calculate the intersection of the two asymptotic thermal stress buildup rates, which directly identifies the cracking temperature. This procedure has a significant advantage in that it makes the BBR a stand-alone device for the determination of the low temperature binder specifications.