Determining the Causes of Top-Down Cracks in Bituminous Pavements

Abstract

Top down cracks (TDC) are longitudinal or transverse cracks that initiate at the pavement surface and propagate downward and outward. They have been observed with increasing frequency on roads in Michigan. In this study, field and laboratory investigations were conducted to determine the factors that affect the load-induced tensile stresses at the pavement surface and the tensile strength of the AC mixes, and hence, affect the susceptibility of the pavement surface to TDC potential. Results of laboratory testing indicate that the AC mixtures used as surface courses in Michigan may be weakened by moisture damage. Further, segregation increases the susceptibility of the AC mixtures to moisture damage, and hence, increases TDC potential. Finally, a crack propagation model was developed as a function of pavement age and degree of segregation based on distress survey data.