Determination of Volume of Aggregates: New Image-Analysis Approach

Abstract

The importance of using quality aggregates with specific gradation and shape properties in asphalt concrete has been recognized by the Strategic Highway Research Program under a set of developed consensus aggregate properties. The flat and elongated ratio and angularity of the aggregate particles are those properties that directly influence the rutting potential of an asphalt pavement. Along with a need to develop rapid and automated methods for determining flat and elongated ratios of individual aggregate particles, there is also a need to develop an accurate and repeatable experimental technique. A new aggregate image analyzer has been recently developed at the University of Illinois that uses three video cameras for accurately determining the volume of each aggregate and for automating the determination of flat and elongated particles, angularity, and gradation. A new image-analysis approach determines the percentage by weight of the flat and elongated particles providing results comparable to the manual results from ASTM D4791 by presenting the results as ratios of weights. The significance of making such accurate volume computations of an individual aggregate using images is discussed. The computed aggregate volumes and the percentages by weight of flat and elongated ratios obtained for two bag samples were in very good agreement with the manual measurements, thus validating the correctness of the imaging technique and the effectiveness of the new aggregate image analyzer.