Top-down cracks (TDCs) in flexible and rubblized pavements constitute a distress that has been reported in the United States and other countries. Researchers have reached different conclusions regarding the causes of TDCs. In this study, field and laboratory investigations were conducted on conventional flexible and rubblized pavements exhibiting TDCs. The engineering characteristics of the pavement layers were obtained from the analysis of field data and laboratory test results. Detailed mechanistic analyses were then conducted using these characteristics to determine the potential for TDCs. The results of such analyses were compared with field data and are presented and discussed in this paper. The results and field data show that (a) surface radial tensile stress induced by wheel loads and enhanced by differential stiffness due to construction, temperature, and aging can cause TDCs, (b) aging of the asphalt binder decreases the tensile strength and the tensile strain at failure of the asphalt mix, and (c) the locations of the maximum surface tensile stress predicted by the mechanistic analysis correspond very well to the locations of the TDCs observed in the field.
Abstract