Characterization of microstructure-transport properties of deteriorated cement paste from computed tomography (CT) images

Pore structure, tortuosity and permeability are considered as key properties of porous materials such as cement pastes in understanding its durability. As such, image analysis techniques were used in this study to quantify pore size, effective porosity, tortuosity, and permeability from the microtomographic images of deteriorated pastes that were subjected to accelerated leaching. At a spatial resolution of 0.5 μm/voxel, the effective porosity (ϴe) was found to be in the ranges of 0.037 to 0.328. The characteristic pore size (d) using local thickness algorithm was found to be in the ranges of 1.406 to 3.589 microns. The geometric tortuosity (τ) based on random walk simulation in the percolating pore space was found to be in the ranges of 2.007 to 7.454. The permeability values (K) using NIST Permeability Stokes Solver ranges from magnitudes 10-14 to 10-17 m2. The results showed that as there is an increase in the effective porosity, geometric tortuosity decreases and water permeability increases. It is also observed that as the geometric tortuosity increases, the permeability decreases. These relationships are in agreement with previous reported literatures that use experimental and image analysis techniques. To model the relationship, the proposed mathematical model obtained is , with a correlation coefficient of 0.948