Advanced Powder Technology, Vol.31, No.7, 3038-3049, 2020
A new method to determine specific surface area and shape coefficient of a cohesionless granular medium
The specific surface area of soil grains (SSA) influences the physical and chemical properties of soil. Despite the widespread application of the SSA, it is often determined by analytical equations or estimated using empirical relationships and visual comparisons. On the other hand, little attention has been paid, especially to three-dimensional and precise measurements. In this study, the precise SSA and shape coefficient was measured in a group of aggregate with different sizes and shapes using a novel method. Geometrical properties such as volume and surface area were measured for each particle using X-ray micro-computed tomography (mu CT) images and image processing. The particle shape coefficient was obtained from the specific surface area and effective diameter. Further, the particle shapes were measured in three distinct characteristics, sphericity, roundness, and roughness. Particle's roundness was measured by Wadell's formula in the plan outline, which did not show an agreement with the shape coefficient. Nevertheless, as the particle sphericity decreases and roughness increases, the shape coefficient is increased. Hence, the shape coefficient of grains was classified based on the sphericity and the surface roughness. The measured SSA and shape coefficient, for 12 gradations with the three different particle size distribution and four different particle shapes, indicated good agreement with predictive analytical relations for rounded and crushed grains and more dissimilarity for flaky and elongated grains. This novel method can provide the quantitative/qualitative classification for non-spherical particles and also improve our understanding on the properties of granular media. (C) 2020 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.