Evaluation of Laboratory Cracking Tests Related to Top-Down Cracking in Asphalt Pavements

Abstract

Top-down cracking (TDC) is now recognized as a prominent mode of failure in asphalt pavements. There has been much research conducted to characterize the failure mechanisms of TDC but there are still large gaps of knowledge regarding TDC throughout the industry. As TDC causes premature failure and costly, unplanned maintenance, there is need for a screening tool that would predict TDC susceptibility in asphalt pavements during design. The objective of this thesis is to evaluate seven surface mixtures with a wide range of properties yielding mixtures that span from predictably TDC susceptible to predictably very TDC resistant. This was done by testing the mixtures using five laboratory cracking tests: Energy ratio, Texas Overlay Test, NCAT Overlay Test, Semi-circular Bend Test, and Illinois Flexibility Index Test. The results of the five tests for each mixture were summarized and will be used to compare mixture laboratory performance to mixture field performance to determine which test most accurately predicted field performance. The results of the study showed that the Energy Ratio produced somewhat predictable results but needs modification to allow for application as a TDC screening tool during design. The SCB and IFIT possessed the lowest variability but produced conflicting results with each other and the expected performance trends. Finally, both Overlay methods exhibited high variability although they most closely followed the expected performance trends. Field performance data are needed to validate any of these findings and will be reported later.