Evaluation of Moisture Durability of Modified Asphalt Mixture with Nano-Titanium Dioxide Using Surface Free Energy Method

Moisture damage is one of the forms of asphalt pavement distress that occurs due to the presence of water and its effect on the mechanical properties of the asphalt mixture. Using nanomaterial as additives is one of the solutions that delays this event and increases the durability of the mixture. In this study, the effect of nanomaterial (nano-TiO2) on the moisture susceptibility of asphalt mixtures was investigated using surface free energy method, indirect tensile strength test (ITS) and resilient modulus (Mr). Asphalt samples were fabricated by neat bitumen with a penetration grade of 85/100 and Siliceous aggregate. The bitumen was modified with 3and 6% (weight of bitumen) of Nano-TiO2. The results of the bitumen section indicate that by modifying the bitumen with Nano-TiO2, the acidic component of surface free energy decreases and its basic component increases. On the other hand, as the non-polar component increases, the bitumen's free energy would be increased. The addition of nano-TiO2 to the asphalt mixture also increased the TSR. TSR reduction through the different freezing-thaw cycles for the modified mixtures was less compared to the control mixtures. The separation energy between bitumen-rock materials is also reduced by modifying the bitumen with this nanomaterial. Therefore, it improves the stripping resistance of the asphalt mixture. In addition, the results of resilient modulus indicate that bitumen modification with Nano-TiO2 increased the Mr values. Similar to changes in the TSR, the RMR value has been increased for the modified HMA and it increased the hot mix asphalt durability.