Introducing Particle Shape Metric (PSM): A fundamental parameter that encapsulates role of aggregate shape in enhancing packing and performance

Abstract

Current packing models for aggregates are robust but they largely prioritize Particle Size Distributions (PSDs). There may be room for further improvement by incorporating aggregate shape. Here, we image up to 250 unique sand particles from 4 different sands and obtain key shape parameters such as Circularity (C), Roundness (R), and Aspect Ratio (AR). Combining these independent parameters, we introduce a new, fundamental parameter – the Particle Shape Metric (P_SM = C.R/AR). Interestingly, this P_SM has a strong correlation with the Packing Coefficient (R² = 0.98), obtained independently from helium pycnometry. Most importantly, P_SM of the sands seems to have a direct influence on the yield stress, compressive strength, and open porosity of a variety of mortar mixtures. These findings highlight the potential role of shape metrics in influencing the granular skeleton of cementitious composites, marking a paradigm shift towards optimizing their workability, strength, and durability.