Long-term field evaluation and analysis of top-down cracking for Superpave projects

Abstract

A field evaluation of cracking performance was undertaken for 10 pavement sections as part of a long-term Superpave monitoring project. It was found that top-down cracking was the major type of cracking. Also, moisture damage was identified in four of these sections. An analysis based on the energy ratio (ER) parameter showed that the mixtures that were affected by moisture generally exhibited a much faster reduction in the ER (indicating reduced fracture resistance) than those that were not. Further analysis of cracking performance was conducted using the enhanced hot mix asphalt fracture mechanics-based pavement performance model (HMA-FM-E). The HMA-FM-E is capable of predicting the entire process of top-down cracking from the onset of cracking until pavement failure, and thus provides more valuable information that may better assist material and pavement engineers to optimise their designs. The results showed that the predictions for sections not affected by moisture generally agreed well with field observations. More importantly, it was identified that the key to further improve the accuracy of the performance model is to more accurately predict changes of mixture properties affected by moisture in addition to oxidative ageing.