Impact of coarse aggregate type and angularity on permanent deformation of asphalt concrete

Abstract

This paper presents a method of evaluating the effect of coarse aggregate type and angularity on hot mix asphalt (HMA) properties and its relationship to the Permanent Deformation resistance. Permanent Deformation is the major pavement distress indicator commonly noted worldwide and is influenced by the properties of the material within the asphalt concrete mix. HMA mixes were prepared using varying coarse aggregate angularity properties such as low, medium and high for two aggregate types. The standardized test methods for classification of aggregate angularity are biased because of the judgement of the test personnel, therefore the study employed the use of the Aggregate Imaging System (AIMS) to evaluate the angularity characteristics. The permanent deformation was measured using the repeated dynamic creep loading test. The research concluded that aggregate type as well as coarse aggregate particle angularity had a significant effect on the Permanent Deformation performance, and also that with an increase in coarse aggregate angularity there was an increase in the resistance of mixes to Permanent Deformation. A comparison between the measured data and predictive data of permanent deformation predictive models showed the limits of existing prediction models. The numerical analysis described the permanent deformation zones and concluded that angularity has an effect on the onset of these zones. Prediction of permanent deformation helps road agencies and by extension economists and engineers determine the best approach for maintenance, rehabilitation, and construction of new road infrastructure.