Explaining Overlay Tester Results with Digital Image Correlation and Finite Element Analysis

The overlay tester (OT) is a relatively new testing procedure that characterizes the fatigue cracking resistance of asphalt mixtures by evaluating the number of cycles to failure of a specimen. The uncertainty of the results has been a concern to some transportation agencies. A careful experimental evaluation of the OT test protocol reveals the complex stress and strain distributions that should be understood before improving the test. Thus, a study was conducted using the digital image correlation (DIC) and finite element analysis (FEA) methods to analyze the OT testing process and results. The DIC technology can be used to visualize the loading responses of the asphalt specimen and correlate them with the experimental results. The FEA, in addition to predicting the behavior of the HMA, can be used to validate the DIC. Thus, the use of these two methods leads to a better understanding of the OT procedure.