Evaluation of Nano Hydrated Lime on the Moisture Susceptibility of Asphalt Mixtures Using Surface Free Energy

Moisture damage is one of the common causes of asphalt pavement failure in moisture presence. To reduce this damage, different additives such as lime, liquid anti stripping, etc. is conventionally added to mix. In this study, the effect of nano hydrated lime (NanoHL), on the moisture susceptibility of asphalt mixtures was investigated by applying surface free energy principals, indirect tensile strength and resilient modulus tests. The asphalt specimens were prepared with granite aggregate and neat bitumen of 60/70 penetration grade containing 0%, 3% and 6% NanoHL by bitumen weight. The results of this study indicate that modification of bitumen with NanoHL decreases the acidic component of surface free energy and increases its basic components. So these changes improve the adhesion between the bitumen and aggregate. Also, cohesion free energy of bitumen is improved by an increase in a nonpolar component of bitumen. Furthermore, the results of the indirect tensile strength test and resilient modulus test indicate that the addition of NanoHL in mixtures causes an increase in ITS and Mr values of modified HMA. On the other hand, the debonding energy of bitumenaggregate for bitumen modified with this Nano material was decreased. This led to an increased resistance to moisture damage.