Quantitative study on the influence of fly ash content, saturation degree and interface transition zone on the permeability of cement-based materials

The interfacial transition zone (ITZ) and fly ash content affect the transmission performance of concrete by altering its pore structure, while varying water content also has distinct effects on transport characteristics. Therefore, this paper investigates the effects of ITZ, fly ash content, and saturation degree on the gas transport performance of concrete materials through gas penetration tests, mercury injection tests, scanning electron microscopy (SEM), and backscattered electron (BSE) imaging. The influences of these factors on the intrinsic permeability of concrete materials are quantitatively analyzed through methods such as parallel test comparative analysis, regression analysis, function fitting, and fixed parameter analysis. The results indicate that the incorporation of fly ash can refine the pore structure of concrete, but it also leads to an increase in intrinsic permeability. The relationship between saturation degree of concrete and intrinsic permeability conforms to an exponential function. Under the same volume fraction, the intrinsic permeability of ITZ is hundreds of thousands of times higher than that of mortar matrix.