The effects of nano zinc oxide (ZnO) and nano reduced graphene oxide (RGO) on moisture susceptibility property of stone mastic asphalt (SMA)

Abstract

Moisture damage is one of the most common and main distresses in asphalt pavements. Using Nanomaterials due to their unique and outstanding properties in the asphalt pavement industry has received much attention in recent years. This paper investigated the effects of Nano Zinc Oxide (ZnO) and Nano Reduced Graphene Oxide (RGO) on moisture susceptibility resistance of Stone Mastic Asphalt (SMA) mixtures. SMA mixtures are a type of hot mix asphalt (HMA) containing two main parts of coarse aggregates and bitumen-filled mortar (bitumen, stabilizing additives, and filler aggregates). There is a wide range of test methods for evaluating the moisture resistance of asphalt mixtures; this study used the immersion Marshall test, indirect tensile strength test, boiling water test, static creep test, pull-off adhesion, and Semi-circular bending (SCB) fracture test for this aim. The pure bitumen was modified with three content of Nano ZnO and Nano RGO (0.2 %, 0.4 %, and 0.6 % by weight of asphalt binder). The experimental results obtained in this research indicated that the addition of Nano RGO in pure binder increases the softening point and viscosity and decreases the penetration and ductility properties of pure bitumen. Also, the addition of Nano ZnO in bitumen can increase the ductility, softening point, and viscosity, and decrease the penetration properties of pure bitumen. The mechanical test results showed that an increase in the percentage of Nano ZnO and RGO lead to a rise in Marshall Stability, indirect tensile strength, accumulated strain, pull-off adhesion strength, and fracture energy and improve the bitumen coating on aggregates in SMA mixtures. According to calculated moisture susceptibility indices of the mentioned tests above, the Nano ZnO and Nano RGO can significantly improve the resistance of stone mastic asphalt mixtures against moisture susceptibility. Examination of the test results showed that the ITS, pull-off, and Semi-circular bending (SCB) fracture test can give a good estimation of the moisture susceptibility of asphalt mixture. In addition, the results of the ANOVA test depicted that in ITS, Pull-off, and SCB fracture tests, Nano ZnO has a more significant effect on improving moisture susceptibility than Nano RGO.