Effect of Aggregate Angularity on Base Material Properties

This paper summarizes the results of tests on the impact of aggregate angularity on the resilient modulus and shear strength of the base/subbase layers in a pavement structure. Tests conducted with large-scale samples (300 mm in diameter) found that, at low bulk stress levels, the resilient modulus of 0% crushed (natural) material was higher than for 100% crushed mixture. This trend was reversed when the bulk stress was greater than 300 kPa. The void ratio also had an impact on the resilient modulus when the crushed content was 50% or less. It was also found that with standard 150-mm-diameter samples, the resilient modulus was higher for the natural material than for 100% crushed material at all stress levels; it was also about 35–50% higher than from the large-scale tests. From the standard samples, the angle of internal friction ranged between 41 and 46° for void ratios around 0.22. For the large-scale samples for a void ratio around 0.16, the angle of internal friction was about 50°. The particle index is a good indicator of the crushed (angular) content of a given base course. For all practical purposes, the particle index is not a good indicator of the resilient properties of the base course aggregate.