Optimization Design of the Mix Ratio of a Nano-TiO2/CaCO3-Basalt Fiber Composite Modified Asphalt Mixture Based on Response Surface Methodology

This research optimizes the mix ratio of nano-TiO2/CaCO3(NTC)-basalt fiber (BF) composite modified asphalt mixture. Based on the Box-Behnken method and the response surface method, a three-factor and three-level test was designed. The input indicators were the asphalt-aggregate ratio, NTC content, and BF content. The output indicators were the density, air voids, Marshall stability, flow value, voids in mineral aggregate (VMA), and voids filled with asphalt (VFA) values of the asphalt mixture. The response surface model was established according to the test response index value. Then, the function was fitted through multiple regression equations and multivariate analysis of variance was performed. Finally, according to the specification requirements and engineering needs, the selected conditions of each response value were determined to optimize the asphalt-aggregate ratio and the contents of NTC and BF, and the predicted values were verified through the measured data. The test results show that the optimal contents of NTC and BF and the optimal asphalt-aggregate ratio were 5.1%, 3.9%, and 5.67%, respectively. By comparing the measured Marshall test index value with the predicted value, the minimum relative error was 0.096% and the maximum error was 6.960%. The results show that response surface methodology can be used to optimize the mix ratio of composite modified asphalt mixtures.