Experimental study of gas diffusion in cement paste

This paper presents an experimental study of gas diffusion in binary mixtures of hydrogen–nitrogen and xenon–nitrogen through cement pastes (CEM I and CEM V) of different water/cement ratios (0.35 and 0.45). First, the impact of water saturation on gas diffusion is investigated by performing tests on samples pre-conditioned in specific atmospheric conditions (dry, 55, 70, 82, 93 and 100% RH) by means of saline solutions. The comparison of the results obtained for the CEM I and the CEM V samples (w/c ratio of 0.45) demonstrate the importance of pore size distribution/connectivity on gas diffusion. Second, diffusion tests at different total pressures and using two different mixtures (hydrogen–nitrogen, xenon–nitrogen) are performed to study the nature of gas diffusion in cement paste. Results demonstrate that gas diffusion in cement paste is controlled by Knudsen and ordinary diffusion at pressures greater than 100 kPa and mainly by Knudsen diffusion at pressures less than 100 kPa.