Influence of Crystal Structure, Morphology, and Microstructure on Fracture Behavior of Natural Silica Sand at Particle Scale

Abstract

The strength properties of individual sand grains play a critical role in understanding the macroscopic performance of granular materials in geotechnical and material science applications. This paper investigates the tensile strength of single-crystalline and noncrystalline sand grains, focusing on Ottawa ASTM 20-30 grains and Ottawa sand grains from Le Sueur, Minnesota. A Deben Microtest loading system was used to conduct quasi-static compression experiments at a constant displacement rate of 0.2    mm / min . Prior to testing, the grains were scanned using microcomputed tomography (micro-CT) to analyze internal structure such as cracks, voids, and mineral inclusions. Additionally, confocal micro-X-ray fluorescence (μXRF) was employed to characterize the elemental composition and distribution within the sand grains, providing complementary data on mineral inclusions and high atomic number elements. This multimodal approach enabled a comprehensive investigation into the relationship between microstructural features, elemental composition, and mechanical performance, offering critical insights into the deformation and failure mechanisms of granular materials. The results revealed that microstructural features significantly influence the mechanical response of sand grains. Grains with fewer cracks, smaller voids, or higher concentrations of elements with high atomic numbers exhibited greater tensile stress at failure. Additionally, morphology played a pivotal role, with grains exhibiting smoother, ellipsoidal shapes exhibiting higher tensile strength. The study demonstrates the importance of integrating micro-CT analysis with mechanical testing to establish correlations between grain-scale properties and macroscopic behavior. These findings provide a deeper understanding of the deformation and failure mechanisms of granular materials, offering insights into geotechnical applications and granular material design.