Evaluation of Susceptibility of High-Temperature Performance of Asphalt Mixture to Morphological Feature of Aggregates by Fractal Theory

Abstract

Morphological characteristics of aggregates have been regarded as a significant factor related to the high-temperature performance of asphalt mixtures. Fractal theory was used to calculate the fractal dimension to evaluate the morphological characteristics of aggregates. Dynamic creep test was selected to estimate the high-temperature performance of asphalt mixtures in terms of gradation types, nominal maximum aggregates sizes (NMAS), asphalt binders, and gyration levels. For each of these factors, correlation analysis between high-temperature indicators and fractal dimension was conducted. The results indicate that the flow number (FN) Index, that is, the ratio of maximum microstrain to flow number, is well-correlated with the fractal dimensions of asphalt mixtures in terms of gradation types and NMAS. Strain rate was a more comprehensive indicator linked with the morphologies of aggregates. According to fractal analysis, the specimen of AC-13 revealed optimal high-temperature resistance in terms of morphology. The AC-13 mixture with 75 gyrations had the largest value of fractal dimension and exhibited the best high-temperature performance. In addition, fractal dimensions measured by box-counting and sandbox methods were well-correlated with indicators of high-temperature ability; box-counting presented advantages for computing the fractal dimension of asphalt mixture.