The physical characteristics of aggregates have an important influence on the behavior not only of unstabilized bases but also of asphalt concrete and portland cement concrete mixes. Experimental techniques using modern data acquisition methods for measuring and analyzing aggregate characteristics are described. A pencept penpad digitizer accurate to 0.0015 In. Together with an ibm-xt microcomputer was used to collect and analyze the necessary data for measuring aggregate shape, surface area, and roughness. Measured coordinates of critical points were stored in an autocad dxf file. The data were edited using a basic program and then transferred to lotus 1-2-3 with which they were analyzed and presented in the form of graphs, tables, and histograms. All data transfer and manipulation were performed electronically. Methods for shape and surface area measurement, classification, and interpretation were reviewed. Two different techniques for measurement of aggregate surface area were compared and demonstrated to yield reasonably similar results. A special shadow techniquefor studying the characteristics of particles smaller than the no. 8 Sieve was described. In addition, the accuracy of the digitizer procedure for measuring surface roughness was assessed. This paper appears in transportation research record no. 1301, Factors affecting properties and performance of pavements and bridges 1991.
Abstract