Investigation on parameters optimization for gas permeability testing of concrete: Inlet-gas pressure and confining pressure

Abstract

Permeability is an important characteristic associated with the durability of cementitious materials. Gas permeability testing could overcome some shortcomings of traditional methods but its key parameters have so far not been identified for long periods, reducing comparability of test results. In this study, coarse-aggregate settlement in concrete was taken into consideration by dividing concrete cores into smaller segments and the gas-permeability of concrete specimens was measured by the modified CemBureau method. Apparent gas-permeability (Ka) values of the segments were determined under multiple inlet-gas pressures (1.0 bar–40.0 bar) and various confining-pressures (30 bar–90 bar), which then were applied to calculate the intrinsic permeability (Kint) values and Klinkenberg coefficient (βk) to obtain optimal parameters of inlet-gas pressure and confining-pressure. Meanwhile, X-ray computed tomography (X-ray CT), mercury intrusion porosimetry method (MIP) and specific gravity method (SG) were used for auxiliary calibration of test parameters. The results showed that four zones with different inlet-gas pressures were observed for apparent gas-permeability: unstable zone, metastable zone, stable zone, and anamorphic zone. Combined with gas-permeability, pore characteristics were employed for auxiliary calibration of parameter optimization. In sum, 15.0 bar–30.0 bar inlet-gas pressure and 50 bar confining-pressure were determined as the best parameters for concrete gas-permeability testing.