The Continuing Search for a HMA Cracking Test: Single Shot versus Repeated Load Testing

摘要

Hot mix asphalt (HMA) overlay is one of the most commonly used methods for rehabilitating deterioratedpavements. One major type of distress influencing the life of an overlay is reflective cracking. Currently, the TexasDepartment of Transportation (TxDOT) uses the Overlay Tester to evaluate the cracking susceptibility and fractureresistance of HMA mixes under repeated loading mode in the laboratory. This study evaluated the prospects of usingthe Overlay Tester (OT) to perform a rapid monotonic loading "single shot" test as a practical method forcharacterizing the fracture properties and cracking resistance potential of HMA mixes. HMA mixes that aretypically used on Texas highways were tested and analytical models were developed to compute the HMA fractureparameters; namely the tensile strength, tensile strain at peak failure load, tensile modulus, and the fracture energy.Both the magnitude and variability of these fracture parameters were found to be comparable with the variabilityassociated with the other monotonic fracture tests for HMA mixes. However, while variability was found to belower, the OT monotonic test (tensile strength, strain at peak load, tensile modulus, and fracture energy) was not aseffective as the standard repeated loading OT test (i.e., using the number of cycles) in terms of screening anddiscriminating mixes or being sensitive to changes in the asphalt-binder content or temperature variations. It isconcluded that the repeated load test, which incorporates a crack propagation phase, is a much better discriminatorof HMA cracking potential than any monotonic loading "single shot" test.