Investigating the effects of using nanomaterials on moisture damage of HMA

In the past few years, several studies have been conducted focusing on the use of nanomaterials as additives in asphalt mixtures. Nevertheless, the effects of these additives on the moisture susceptibility of asphalt mixtures have not been studied. In this study, the effects of using nano-CaCO3 as an antistrip additive on moisture susceptibility of asphalt mixtures have been assessed using the surface free energy (SFE) method and modified Lottman test. Hot mix asphalt (HMA) samples were made with asphalt binders containing 0, 2, 4 and 6% of nano-CaCO3 and two sources of aggregate, namely limestone and granite. One, three and five freeze-thaw cycles were applied to HMA samples in a modified Lottman test to explore the effect of nanomaterials, clearly. The results of the modified Lottman test show that the wet/dry ratio values of indirect tensile strength (ITS) for mixtures containing nanomaterials were higher than those of control samples. In addition, the results of the SFE method indicate that nano-CaCO3 increases the wettability of the asphalt binder on the aggregate and promotes the adhesion between the asphalt binder and aggregate. Adding nanomaterials leads to the decrease of the acid component of SFE and increases the basic component of SFE of the asphalt binder that leads to an increase of adhesion between the asphalt binder and sensitive aggregate against moisture damage.