EVALUATING THE INTRINSIC PERMEABILITY OF CEMENTITIOUS MATERIALS USING A FALLING-HEAD GAS PERMEAMETER.

This paper explores a new approach to estimating the pressure-dependent gas permeability of a cementitious material when using a falling-head gas permeameter. A series of experiments were performed on mortars with varying mixture proportions, and measurements were made with different initial applied pressures. The governing equation is based on an analogy to a falling-head liquid permeameter, but accounting for the gas compressibility and the pressure-dependent Klinkenberg effect that can occur during gas permeation. This formulation overcomes a limitation of other approaches that depend on the initial pressure that is applied and on the range of data that can be considered when evaluating transport properties. Analyses of the experimental data confirm that the apparent permeability is inversely proportional to the pressure applied as per the Klinkenberg equation. By accounting for this effect, it is possible to determine an intrinsic permeability that is independent on the pressure, and is a true characteristic of the pore space available for gas transport.