Gas permeability of macro-cracked concrete: effect of temperature and water saturation

This experimental work investigates the hydraulic behavior of a macro-cracked concrete, in order to improve the understanding of the coupled effects of temperature and water saturation. A concrete sample is macro-cracked using the Brazilian test technique. It is then submitted to dry or wet gas flow at different temperatures and confining pressures and its permeability is recorded. This first phase of the study clearly shows that confinement, which induces macro-crack closure, drives the first-order variation of permeability without any significant self-sealing of the crack, despite the wet gas injection. On another hand, injection of liquid water leads to a continuous decrease in flow rate. In a second phase, the permeability of intact, uncracked, material is measured under different moderate temperatures, which generates sample cooling or heating. This phase clearly demonstrates the importance of the sample initial saturation rate. Indeed, if the material is initially dry, temperature plays no role upon permeability, whereas it does if the material is initially partially water-saturated.