Effect of Pavement Responses on Fatigue Cracking and Cement-Treated Reflective Cracking Failure Mechanisms

Mechanisms of flexible pavement fatigue cracking and reflective cracking from a cement-treated base (CTB) layer were investigated. 3D finite-element (FE) models were developed to simulate typical pavement structures for low-, medium-, and high-volume traffic. The FE models simulated a dual-tire assembly as well as surface vertical and tangential contact stresses. The FE model was validated using stress and strain measurements obtained from the Louisiana Accelerated Loading Facility. The shrinkage strain induced by a CTB layer was converted to displacement in the base layer and was used to simulate the tensile stresses caused by shrinkage cracking. Results showed that the initiation of surface fatigue cracking is due to vertical shear strain within the AC layer exacerbated by high tensile strain at the surface due to loading. Furthermore, the incorporation of transverse tangential stresses increased the surface tensile strains by more than 50% regardless of the asphalt concrete (AC) layer thickness. However, longitudinal tire contact stresses had minimum effect (less than 10%) on the surface and bottom AC tensile strains. Tensile stresses due to shrinkage strains in the CTB were observed to be higher than the tensile strength of the material after a few weeks of curing, suggesting the potential initiation of shrinkage cracks shortly after construction. The addition of fly ash to the CTB may significantly reduce reflective cracking potential after construction.