Microstructural characterization of asphalt mixtures containing recycled asphalt materials

Most studies addressing the use of recycled asphalt materials in asphalt paving mixtures are based on experimental tests and performance evaluation. Investigating the effect of adding recycled materials to the microstructure of asphalt mixtures has received little consideration. For example, higher-order microstructural information can be used in place of simple volumetric information as input in micromechanical models that can more accurately predict the effective properties of asphalt mixtures. In this paper, the influence of adding three different recycled materials, reclaimed asphalt pavement (RAP), manufacturer waste scrap shingles (MWSS), and tear-off scrap shingles (TOSS), on the microstructural distribution of the aggregate phase is investigated using digitally processed images of asphalt mixtures and numerical evaluations of two-and three-point correlation functions. No significant variations are found among the gradation curves, and minimal differences were observed for two-and three-point correlation functions. This indicates that the addition of the recycled materials does not significantly affect the aggregate spatial distribution of asphalt mixtures. However, an increase in autocorrelation length was found for some of the mixtures containing recycled shingles.