Tpo-Down Cracking Analysis and Control for Asphalt Pavements

In recent years, there are increasing evidences that suggest most single or parallel longitudinal cracks under wheel path initiate at the surface course and propagate downward (Top-down crack). In general, these types of cracks occur on the heavy-duty pavements, therefore they are perceived heavy load-related. In order to analyze the mechanisms that cause the top-down cracks, a device to measure the distribution of the contact pressure between the real tire and the pavement was developed. With this device, the contact pressure distributions of 91 cases covering 5 types of real tire were measured. Based on the measured results, the mechanical analysis of typical heavy-duty pavement structures was conducted with 3D Finite Element Method (FEM). Through the comparison between the position and direction where the maximal stresses locate at and where the top-down cracks initiate at, the repeated shear stress under the non-uniform contact pressure between tire and pavement was considered to be the main causation of the top-down cracks. The control of the shear strength of the mixture is one of the measures to control the top-down cracks. For this reason, a uniaxial penetration test (UPT) to measure the shear strength of mixture was developed based on the similarity principle, and the corresponding test parameter and data process method were presented. For the covering bastract of this conference see ITRD number E215163. (A)