Pore structure characteristics and permeability analysis of natural anhydrite with various water /anhydrite ratios based on mercury intrusion porosimetry

The characteristics of the gypsum pore structure are closely related to its macroscopic mechanical properties and permeability. Recent research on anhydrite-based cementitious materials is mainly focused on modification and enhancement and their effect on pore structure characteristics, while the relationship between pore structure and permeability remains unclear. Here, we characterized the pore structure and permeability of natural anhydrite-based cementitious material under various water-anhydrite (W/A) ratios based on the mercury intrusion porosimetry, intending to investigate the relationship between these two parameters. This paper investigated the effect of the W/A ratio on the characteristic pore diameter of natural anhydrite-based cementitious materials. The hydration products optimize the pore structure through the filling effect to form a dense spatial structure, thereby improving the mechanical properties and permeability of the hardened body, where porosity is the main factor affecting the mechanical properties. The multifractal characteristics of natural anhydrite-based cementi-tious materials and the pore size dependence of permeability were clarified, and the thermal fractal dimension of its small pore range (4-1 600 nm) satisfied the k = aDb relationship with the permeability coefficient based on the Katz-Thompson model, providing a novel thought for the calculation and research of the permeability of anhydrite-based cementitious materials.