Laboratory Hot-Mix Asphalt Cracking Testing

Abstract

Cracking is one of the predominant distresses occurring in hot-mix asphalt (HMA) pavements and often costs highway agencies millions of dollars in road maintenance and rehabilitation activities. One way to minimize this distress is through material screening and selection of appropriate mix designs that are representative of crack-resistant HMA. However, there are no universally adapted standardized laboratory cracking test methods for routine mix design and screening purposes for HMA mix crack resistance. In this study, three repeated loading cracking test methods—namely, the repeated loading overlay tester (OTR), repeated loading indirect tension (R-IDT), and repeated loading semicircular bending (R-SCB)—were evaluated and compared for their potential application as surrogate tests for routine crack evaluation and screening of HMA mixes in the laboratory. The evaluation criteria, based on commonly used Texas HMA mixes, included (a) the potential to differentiate and screen mixes readily, (b) the sensitivity to mix design variables such as variations in the asphalt binder content, (c) repeatability and statistical variability, (d) correlation to field performance data, and (e) the practicality of implementation. Overall, the OTR test, with a proven correlation to field performance data, exhibited statistical superiority as a practical repeated loading crack test method for routine HMA mix design and screening, followed by the R-IDT test. However, although the R-IDT test exhibited superiority concerning sample fabrication simplicity, validation with field data remains one of the key challenges to be addressed with this test. The R-SCB test was the least repeatable, particularly at high asphalt binder content levels, and appears to be better suited for low-temperature testing.