Analytical and Laser Scanning Techniques to Determine Shape Properties of Aggregates

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 nonideal shapes. This paper presents selected results from the use of a laser-based scanning technique to determine the form of aggregates employed in construction of pavements in South Africa. A three-dimensional (3-D) laser scanning system was used to examine aggregate materials from various sources, and the data were processed to reconstruct 3-D models of the aggregate particles. The models were further analyzed to determine the properties of the forms. Two analysis approaches based on physical properties of the aggregate and spherical harmonic analysis were employed to determine the form indices, and the results were compared. The indices based on the physical properties included (a) sphericity computed from the surface area and volume, (b) sphericity computed from three orthogonal dimensions, and (c) the flat-and-elongated ratio computed from the longest and shortest dimensions of an aggregate particle. Good correlations were observed between the form indices from the aggregate physical properties and the spherical harmonic form index. One conclusion of the research is that the laser scanning technique can be employed to quantify better the form properties of aggregate materials used in pavements.