Modified dynamic modulus test and customised prediction model of asphalt-treated drainage layer materials for M-E pavement design

The past two decades have seen great developments and application of asphalt treated open-graded mixtures as a drainage layer in pavement in the United States. Nevertheless, the previous research has also indicated weak mechanical properties of the drainage layer compared with dense-graded asphalt concrete. This study sought to quantify the stiffness of the drainage layer materials for incorporating them into a mechanistic-empirical pavement design framework. It was found in this study that both the current dynamic modulus test method and the empirical prediction model, which were developed for dense-graded asphalt concrete, may not be applicable to drainage layer mixtures with high porosity. Under this circumstance, a modified dynamic modulus test and a calibrated model to predict the dynamic modulus for drainage layer materials have been developed based on the AASHTO TP 342-11 test method and the NCHRP 1-37A model in this study.