Characterization of the fatigue behavior of asphalt mixture under full support using a Wheel-tracking Device

Abstract

Most existing fatigue testing methods in the laboratory are designed to evaluate the cracking resistance of asphalt mixture only, regardless what types of structural support it is used in the field. However, literature has confirmed that fatigue cracking is a structural related distress, and the cracking potential of asphalt layer is strongly affected by its underneath structural supporting conditions. On the other hand, the Hamburg Wheel-tracking Device (HWTD) has gained popularity for characterizing the rut-resistance and moisture susceptibility of asphalt mixtures under moving loads among state Department of Transportation (DOT) and agencies, and it has the capability to be modified to specify supporting conditions. Therefore, in this study, we propose to make some modifications to the existing HWTD and to study its capability of being also utilized as a cracking device for its potential advantages in equipment availability and simulating field loading and structural conditions. The developed HWTD fatigue test was used to simulate the conditions experienced by an asphalt mixture layer paved on the flexible base and applied with a vertical moving load. Three mixtures were specially designed to have known fatigue behavior difference for evaluating the reliability of this newly developed method, and to be compared with the standard American Association of State Highway and Transportation officials (AASHTO) semi-circular bending (SCB) method (AASHTO TP 124-18). A variety of strain and pressure gauges were used to record the load responses for fatigue behavior analysis. Both the phenomenological fatigue life analysis approach and the dissipated energy based ratio of dissipated energy change (RDEC) approach were used for data analysis. It was found that the HWTD fatigue test was essentially a type of laboratory scale accelerated loading test which can simulate the fatigue cracking phenomenon under the proposed testing setup. The RDEC approach with different failure criteria were suitable and effective in analyzing the testing data and can quantify the fatigue behavior of specific mixture within reasonable time frame. The results were consistent with the standard SCB fracture test results. In conclusion, the HWTD fatigue test has the potential to be a rational and convenient method for characterizing the fatigue behavior of hot mix asphalt (HMA) materials with the consideration of supporting conditions.