Development of Three-Dimensional Image Analysis Techniques to Determine Shape and Size Properties of Coarse Aggregate

Abstract

A new aggregate image analyzer, UIAIA, was developed to provide a reliable means for automating the determination of coarse aggregate size and shape properties. This new device uses 3 cameras to collect aggregate images from three orthogonal directions. The use of 3 images for each particle provides the unique capability to accurately reconstruct the three-dimensional shape. This makes it feasible to compute the volume of each aggregate particle accurately, so that test results can be expressed in percentages by weight. The software developed for this system is capable of determining the volume (and hence weight) of each particle and its minimum, intermediate, and maximum dimensions. Based on the particle dimensions, its flat and elongated ratio, and the controlling sieve size can be computed. In addition, a new angularity index based on image analysis principles has been developed. This index is calibrated in a manner that allows for a clear distinction to be made between crushed stone and rounded gravel particles. The main focus of this doctoral study was with regard to the development of imaging techniques to perform these aggregate shape and size property tests.