Analytical and laser scanning techniques to determine shape properties of mineral aggregates

Abstract

The fundamental shape attributes of aggregates used in pavements i.e., form, angularity, and surface texture have not been accurately quantified historically, because of their irregular and non-ideal shapes. This paper presents selected results using a laser-based scanning technique to determine the form of aggregates used in construction of pavements in South Africa. A three-dimensional (3-D) laser scanning system was used to scan aggregate materials from different sources, and the data were processed to reconstruct 3-D models of the aggregate particles. The models were further analyzed to determine the form properties. In this paper, two analysis approaches, based on aggregate physical properties and spherical harmonic analysis, were employed to determine the aggregate form indices. The aggregate form indices obtained from the physical aggregate properties were compared with the form indices computed based on the spherical harmonic analysis. The indices based on the physical properties include sphericity computed from the surface area and volume, sphericity computed from three orthogonal dimensions, and flat and elongated ratio computed from the longest and shortest dimensions of an aggregate particle. Good correlations were observed between the form indices obtained from the aggregate physical properties, and the spherical harmonic form index. It is concluded that laser scanning technique could be employed to better quantify the form properties of aggregate materials used in pavements.