Effects of various shape parameters on packing of aggregate particles

Abstract

The shape of the aggregate particles used has significant effects on the properties of the concrete produced. One major effect is on the packing density of the aggregate which determines the amount of cement paste needed to fill the voids between the aggregate particles. In order to study how the various shape parameters of aggregate particles would affect the packing of aggregate, aggregate samples of different rock types from different sources have been analysed for their shape characteristics using a newly developed digital image processing technique and their packing densities measured in accordance with an existing method given in the British Standard. The packing densities of the aggregate samples are correlated to the shape parameters to evaluate the effects of the various shape parameters on packing. From the results of the correlation, it is found that the shape factor and the convexity ratio are the most important shape parameters affecting the packing of an aggregate. Two alternative formulas revealing the combined effects of these two shape parameters on the packing density of aggregate are proposed.