New Methodology for Shape Classification of Aggregates

Abstract

Aggregate shape characteristics play a major role in determining the structural and functional properties of asphalt mixes. A comprehensive, statistically based methodology for the analysis and classification of the shape characteristics of both fine and coarse aggregates is presented. These characteristics are form (three dimensions of coarse aggregates), angularity, and surface texture. The methodology was developed by measuring the distribution of the shape characteristics of aggregates from a wide range of sources and varying sizes. The limits for the classification groups were determined with the use of a cluster analysis. The new methodology offers several advantages over current methods used in practice. It is based on the distribution of shape characteristics in an aggregate sample rather than on average indices of these characteristics. The coarse aggregate form is determined with the use of a three-dimensional analysis of particles, which allows particles to be distinguished between flat, elongated, or flat and elongated particles. The fundamental gradient and wavelet methods were used to quantify angularity and surface texture, respectively. The classification methodology can be used to evaluate the effects of different processes, such as crushing techniques and blending, on aggregate shape distribution. It also lends itself to the development of aggregate specifications on the basis of the distribution of shape characteristics.