Optimization design of sand-containing fog seal overlay on chip seal based on response surface methodology

To improve the durability of the chip seal and reduce the chip loss rate, a sand-containing fog seal was covered on its surface, and the response surface methodology (RSM) was adopted to optimize the mix proportion. The amount of emulsified asphalt and sand-binder ratio were selected as key factors, and experimental research was conducted with anti-skid performance, texture depth, and Vialit mass loss rate as response indicators. The results indicate that the regression model established between response values and factors exhibits good fitting degree. The increase of emulsified asphalt can significantly improve the bond strength, but it will reduce the anti-skid performance. The increase in sand-binder ratio helps to improve the pendulum friction value, but it will reduce the texture depth. For chip seal of 3-5 mm and 5-10 mm, it is recommended to use emulsified asphalt at 0.46 kg/m2 and 0.62 kg/m2, and a sand-binder ratio of 0.58 and 0.70, respectively. The optimized sand-containing fog seal exhibits good water sealing performance and reasonable open traffic time, which can significantly improve the durability and road performance of the chip seal. The research provides theoretical basis and technical support for the material design and engineering application of sand-containing fog seal.