Quantitative Evaluation of Aggregate Gradation Based on Synergistic Mechanism of Geometric Characteristics, Size and Passing Rates

The current gradation design of asphalt mixtures relies solely on sieve passing rates of single-sized aggregates. The quantitative evaluation of aggregate gradation is a challenge, considering the combined action of the geometric characteristics, size and passing rates of the aggregates. Analyzing the multi-dimensional geometric synergistic characteristics of graded aggregate can help to quantify the gradation. The AIMS II system was used to systematically and quantitatively evaluate the shape, angularity and texture of parameter distribution of single-sized aggregates. The synergistic effect of composite geometric characteristics on the mesoscopic interface behaviors was analyzed, and then a calculation model of aggregate gradation characteristic was established based on the gray relational analysis method. The results show that the lithology and source of aggregates govern the geometric characteristics indices of single-sized aggregates, whereas particle size controls the extent to which these geometric characteristics contribute to skeleton stability and interface interactions. A higher proportion of large-sized coarse aggregates results in a greater composite angularity index and a more stable skeleton structure within the asphalt mixture. Texture characteristics and particle size distribution are integrated into a unified composite texture index. As this index increases, the lubrication effect of asphalt on the aggregate skeleton becomes more pronounced. The aggregate gradation characteristic index demonstrates strong discriminative capability for different gradations and exhibits a robust linear correlation with aggregate–asphalt interfacial interaction indices. This index demonstrates strong capability to quantitatively describe the synergistic mechanism of multi-dimensional geometric characteristics and gradation types of asphalt mixtures.