Simple Asphalt Mixture Shear Rutting Test and Mechanical Analysis

Asphalt pavement rutting is caused primarily by shear stresses induced by heavy truckloads. Many tests have been developed to determine asphalt mix rutting potential. However, due to limited correlation with field rutting performance, long testing hours, and difficulties of sample fabricating, no test can be used as a fast and straightforward assessment tool for quality control or quality assurance/acceptance (QC/QA) purpose. In this study, a shearing fixture was developed to investigate the shear rutting potentials of the asphalt mixture more easily and rapidly. An analytical solution was derived from the mechanical analysis. With this solution, the stress distributions of the specimen under the shear loading were analyzed and plotted. These stress distribution plots are also compared with those under the other loading fixtures, such as the indirect tension (IDT) fixture and Marshall fixture. The comparison indicates that the developed shearing fixture is good at inducing shear stress to the specimen and manifesting the shear rutting mechanism. Several scenarios were evaluated by varying the loading fixture configurations, such as the bottom support arc length and angle. The impacts of these configuration elements on the stress distribution were investigated. Laboratory-mixed and laboratory-molded specimens were tested using the shearing fixture, and the test results show high repeatability. The mechanical analysis and experiments indicate that the new shear rutting test is very promising for evaluating the asphalt mix rutting potential quickly and straightforwardly.