Modeling of Gas Permeability Coefficient for Cementitious Materials with Relation to Water Permeability Coefficient

Permeability can not be expressed as a function of porosity alone, it depends on the porosity, pore size and distribution, and tortuosity of pore channels in concrete. There has been considerable interest in the relationship between microstructure and transport in cementitious materials, however, it is very rare to deal with the theoretical study on gas permeability coefficient in connection with carbonation of concrete and the effect of volumetric fraction of cement paste or aggregate on the permeability coefficient. The majority of these researches have not dealt with this issue combined with carbonation of concrete, although carbonation can significantl y impact on the permeability coefficient of concrete. In this study, fundamental approach to compute gas permeability of (non)carbonated concrete is suggested. For several compositions of cement pastes, the gas permeability coefficient was calculated with the analytical formulation, followed by a microstructure-based model. For carbonated concrete, reduced porosity was calculated and this was us ed for calculating the gas permeability coefficeint. As the result of calculation of gas permeability for carbonated concrete, carbonation leaded to the significant reduction of gas permeability coefficient and this was obvious for concrete with high w/c ratio. Mean while, the relationship between gas permeability and water permeability has a linear function for cement paste based on Klinkenberg ef fect, however, which is not effective for concrete. For the evidence of the modeling, YOON’s test was accomplished and these results were compared to each other.Key words : Gas permeability coefficient, Carbonation, Micro-structure, Water permeability, YOON’s test , , . , . , , . . . . - . , Klinkenberg , . YOON’s . : , , , , YOON’s Concrete Engineering