Use of a 3D Structured-Light Scanner to Determine Volume, Surface Area, and Shape of Aggregates

Abstract

The standard method of using a caliper to determine aggregate particle dimensions is not sufficient to describe the shape, texture, angularity, and volume of particles, and there is not a reference method to determine aggregate surface area. A three-dimensional (3D) structured-light scanner seems to be a viable and economical alternative with enough speed to obtain 3D data from hundreds of particles. This work used a 3D scanner to evaluate morphological properties of coarse aggregates and compared results with those from conventional techniques. Two types of aggregates (around 60 particles of each type) were scanned and manually measured by a single operator with a digital caliper using two different methodologies: (1) the minimum bounding box (MBB), and (2) a conventional standard test method (STD). The 3D structured-light scanner proved to be accurate for assessing the morphology, surface area, and volume of coarse aggregates, and with a processing rate of $10\min /\mathrm{particle}$ , it was faster than other techniques such as X-ray computed microtomography (micro-CT) or laser scanning. Compared with the manual method (caliper) or the most commonly used two-dimensional (2D) image analysis techniques, it also was more accurate. The MBB using a caliper overestimated volume by about 17% and underestimated surface area by 11%, which was estimated by assuming an ellipsoid with the dimensions obtained. The 2D circularity had a poor correlation with the 3D sphericity, especially for flat or elongated particles.