Investigation on the effects of gradation and aggregate type to moisture damage of warm mix asphalt modified with Sasobit

Moisture damage is one of the major concerns for warm-mix asphalt (WMA) because it is hypothesised that the reduction in mixing temperature could adversely affect the moisture sensitivity of WMA. The aggregate type and their properties are also one important factor affecting the moisture damage of WMA. This study focused on understanding the effect of aggregate structure and its physical properties on the mechanism of moisture damage in WMA. This study evaluated the moisture sensitivity of hot-mix asphalt (HMA) and WMA as reflected in the permanent deformation. The effects of aggregate gradation and aggregate types on the moisture damage were also evaluated. The results from this study show that WMA is more resistant to permanent deformation than HMA as indicated by lower permanent strain rate and higher flow number (FN). Gradation has an effect on the permanent deformation in granite and slag mixes due to the difference in aggregate properties. WMA is more sensitive to moisture damage than HMA as shown in lower ratios of FN and permanent deformation rate. Fine-graded mixtures appear to have greater resistance to moisture damage than coarse-graded mixtures for both HMA and WMA. The result could be due to the different structure of air void distribution in the mixes of different gradation. It was found that the proper selection of aggregate type and aggregate structure could reduce the moisture damage problem of WMA.