Particle shape analysis of fine aggregate using a simplified digital image processing method

Abstract

The use of manufactured fine aggregates in Portland cement concrete has been increasing in the last years owing to environmental and economic reasons. This type of aggregate normally has flaky and elongated particles that negatively affect workability. Producers have been making efforts to overcome this problem by the use of better crushers capable of improving particle shape. However, even using modern crushers, the particle shape depends on the rock mineralogy and the production variables. Thereby, it is of foremost importance to determine a shape index that can be used both as a production control parameter and for improvements on the aggregate performance. Hence, this paper presents a simplified digital image processing method to measure a particle shape index for fine aggregates based on the concept of volumetric coefficient recommended by French standard AFNOR XP P18-54. The validation tests were undertaken in coarse aggregate samples and showed a very good agreement with manual measurements. Experimental tests were also carried out on mortar samples produced with three different manufactured fine aggregates with distinct shape index measured by the proposed method. The results showed that mortar flow is strongly influenced by the particle shape measured by the proposed method.