Investigation of Surrogate Performance Related Tests for Fatigue Cracking of Asphalt Pavements

This paper studies the relationship between laboratory measurements of fatigue performance and fracture performance of conventional asphalt mixtures, asphalt mixtures with reclaimed asphalt pavement (RAP), and rubberized asphalt mixtures. The existing four-point bending (4PB) test was developed to evaluate the fatigue performance of asphalt pavements; however, it is not necessarily appropriate for use in routine job mix formula approval and is too slow and expensive for quality control/quality assurance (QC/QA). In this paper, the semi-circular bending test and indirect tensile asphalt cracking test (IDEAL-CT) were evaluated for their potential to serve as a simple and fast surrogate fatigue performance related test for QC/QA on routine projects and routine mix design. Multiple representative fracture parameters were obtained from the Illinois flexibility index test and the IDEAL-CT. The coefficient of variation revealed that the lowest variability from both tests was in fracture strength. In addition, the linear regression analysis between fracture parameters and fatigue performance indicated that slopes, fracture toughness, and strength from fracture tests have good correlations with the initial flexural stiffness from 4PB tests, while 4PB initial stiffness is well correlated with fatigue life. The direct correlation between fracture properties and fatigue life was not as good. The fracture parameter “strength” also showed the capability of discriminating among asphalt materials with low RAP content.