Experimental and theoretical study on fine aggregates packing density for higher particle range classes

ABSTRACT The rational use of materials in construction, particularly cementitious materials, is crucial for environmental preservation. One way to optimize this consumption, especially in mortar production, is to study the packing of fine aggregates and their interactions with the cementitious phase. Several factors influence the rheology of such composites, including void ratio and packing density. This study investigates the role of particle size distribution in packing density by applying classical models and a modified approach. Twenty granular sets were analyzed using these theoretical models, considering different numbers of grain size distribution classes. In this work, packing densities were determined using the CPM (Compressible Packing Model) and a proposed alternative method, while natural sand was used to experimentally validate the theoretical results, reproducing nine of the twenty developed sets. From the analyzed grain size distributions, theoretical models were found to fit natural four-class sands, but their accuracy declined when the number of classes exceeded five classes. The results indicated that increasing the number of grain classes enhances packing density up to 7,5% in natural sands, with this effect being more pronounced in sets derived from theoretical models, ranging up to 13%. The correlation between packing density and the uniformity coefficient followed a sigmoidal fit, suggesting that less uniform sands have higher void ratios. Experimental validation of the theoretical results revealed that the packing density values obtained using the CPM model were 11% to 16% lower than the experimental values. The proposed modified model yielded better results, demonstrating less sensitivity to increases in the fineness modulus.