Effect of Nanosilica on Moisture Susceptibility of Asphalt Emulsion Mixture

Moisture susceptibility is a major concern about asphalt emulsion mixtures due to low mixing temperature and compaction. Therefore, herein, nanosilica was used because of its high specific surface, good dispersing ability, and strong adsorption, to improve the moisture susceptibility of asphalt emulsion mixture. The bitumen emulsion was modified with different percentages of nanosilica (0.2, 0.4, 0.7, and 0.9% of the bitumen weight). Then, the indirect tensile strength (ITS) test and compressive strength test were performed to evaluate the moisture susceptibility of the samples. The results demonstrated that the modification of the bitumen emulsion with nanosilica increased the ITS and compressive strength of the samples by improving the bitumen cohesion and increasing the adhesion of the bitumen and aggregates. This resulted in the indirect tensile strength ratio (TSR) and compressive strength ratio (CSR) parameters of 88% and 89%, which had increased by 22.5% and 27%, respectively. Also, the addition of nanosilica significantly increased the secant stiffness modulus and reduced the failure strain of asphalt emulsion mixtures against lateral deformation. The results of the statistical analysis indicated the significant effect of nanosilica addition on reducing the moisture susceptibility and improving the mechanical performance of asphalt emulsion mixtures at the 95% confidence level.