Design Method for Strongly Embedded Skeleton Dense Gradation in Asphalt Mixtures Based on the Vertical Vibration Test Method

To propose a design method for strongly embedded skeleton dense gradation using laboratory tests of the vertical vibration test method (VVTM), the strongly embedded skeleton dense gradation of two typical asphalt mixtures with 16- and 13.2-mm nominal maximum aggregate size was investigated in this study. Based on the packing and filling characteristics of aggregate particles, the proportion of each specification of aggregate in the coarse aggregate (4.75–16 mm) was investigated using theoretical analysis and the VVTM in the laboratory. The results showed that the optimal percentage of voids in coarse aggregates (VCA) and mechanical strength were reached when the aggregate ratio was 70∶30 for double-grade aggregates and 50∶30∶20 for triple-grade aggregates. The I-method was used to investigated the gradation of the fine aggregates (0.075–4.75 mm), and the results showed that the mechanical strength of asphalt mortar was maximized when the I-value was 0.75. The optimum dosage of asphalt mortar is determined by the maximum mechanical strength of the mixture; test results indicated that the optimum dosage of asphalt mortar was 6% larger than the theoretical calculation. Considering the ratio between coarse aggregates, I-value and optimum dosage of asphalt mortar, the range of strongly embedded skeleton dense gradation is determined by the maximum mechanical strength of the mixture. The high-temperature performance, low-temperature performance, and mechanical properties of the strongly embedded skeleton dense gradation were investigated using laboratory tests, and all the results were better than the gradation of asphalt concrete (AC) in the specification.