Fracture testing of aggregates in unbound granular road materials

Aggregate fracture in unbound granular materials (UGMs) can significantly influence the performance of both unbound and bitumen-bound layers. This study introduces a new methodology to characterise aggregate fracture in UGMs through a combined experimental and numerical approach that accounts for gradation variability and applied load magnitude. Confined monotonic uniaxial compression tests were conducted at various load magnitudes, and discrete element simulations of the experiments were used to estimate UGM load–displacement response without aggregate fracture. The experimental results were analysed statistically to quantify the effects of UGM gradation, aggregate type and load magnitude on the extent of aggregate fracture. Differences between the experimental and simulated load–displacement responses at specific load levels were correlated with the measured amount of aggregate fracture for UGMs of different gradations and aggregate types. The proposed parameter shows a unique relationship with experimentally measured aggregate breakage and can evaluate aggregate fracture evolution in UGMs under applied loading.