Three-dimensional transport properties of mortar with a high water-to-cement ratio using X-ray computed tomography

Abstract

Tortuosity is an important parameter for characterizing the flow and transport properties of porous material but impossible to be directly measured experimentally. This study aimed to quantitatively calculate the tortuosity parameter of mortar with a high water-to-cement ratio using X-ray computed tomography (CT)-based random walk simulation. The result was verified by numerical simulation and available experimental data. Using the CT scanned data, the interconnected three-dimensional (3D) pore structure was accurately reconstructed considering the interfacial area of sand particles using a watershed algorithm. The transport properties, such as tortuosity, permeability, and diffusivity, were calculated by performing random walk and numerical simulation on the interconnected 3D pore structure. The random walk analysis indicated that a higher cement content led to a significant increase in tortuosity which represents the evolution of complexity of 3D pore structure. Furthermore, it was verified that the formation factor (i.e., tortuosity divided by porosity) is inversely proportional to the diffusivity of the systems. The quantitatively computed transport properties will be useful to accurately evaluate microstructural properties of mortar systems with high water-to-cement ratios. Furthermore, the methodology developed and verified herein has a potential to be further applied to other porous media such as underground reservoirs and fractured solids.