Optimization Design of the Mix Proportion of Granite Aggregate Hydraulic Asphalt Concrete Based on Response Surface Methodology

[Objective] The adhesion problem between acidic aggregates and asphalt is a key issue in the application of acidic aggregates in hydraulic asphalt concrete. For hydraulic structures, the mix design of hydraulic asphalt concrete incorporating acidic aggregates modified with anti-stripping agents is not entirely the same as that used in road engineering. This study aims to investigate, under a constant gradation index, the individual effects of the proportion of coarse and fine aggregates, as well as their interaction effects with asphalt-aggregate ratio and filler content, on the performance of anti-stripping-agent-modified hydraulic asphalt concrete with granite aggregates, and to optimize the mix proportion design of granite aggregate hydraulic asphalt concrete. [Methods] A Box-Behnken response surface methodology was employed for experimental design. Air voids, flow value, and stability were selected as response variables to establish response surface regression models. The effects of asphalt-aggregate ratio, filler content, and sand ratio, as well as their single and interaction effects on the response values, were analyzed to determine the optimal mix proportion. Meanwhile, water stability tests were conducted to verify the performance. [Results] (1) The mix proportion design of granite hydraulic asphalt concrete was optimized using response surface methodology, and the established quadratic regression equations were able to well describe the relationships among sand ratio, asphalt-aggregate ratio, filler content, and air voids, stability, and flow value. Analysis of variance and significance tests indicated that the model was effective and reliable, with high credibility. (2) Response surface analysis showed that the order of influence on the air voids of granite hydraulic asphalt concrete was asphalt-aggregate ratio>sand ratio>filler content; the order of influence on stability was sand ratio > asphalt-aggregate ratio > filler content; and the order of influence on flow value was sand ratio > asphalt-aggregate ratio > filler content. (3) The three-dimensional distribution of the water stability coefficient indicated that a relatively high water stability coefficient was obtained in the region where the sand ratio ≤ 36%, filler content ≤13.5%, and asphalt-aggregate ratio ≥6.8%. (4) The optimized mix design parameters of granite hydraulic asphalt concrete were a sand ratio of 33%, an asphalt-aggregate ratio of 7.1%, and a filler content of 12.5%. [Conclusion] The experimental results confirm that this mix proportion exhibits good performance and can provide a reference for the optimization design of granite hydraulic asphalt concrete mix proportions in practical engineering.