Correlation between the Transport Properties of the Transition Zone and Its Mineral Composition and Microstructure

The transition zone between hardened cement grout and rock is an area where transport properties differ from elsewhere within the grout. A qualitative method which uses a low electrical field to characterise the diffusivity of the transition zone shows that some physical and chemical properties of the cement grouts are responsible for this microstructural inhomogeneity. In order to better understand the mineral composition and microstructure of the hardened cement grout-rock interface, differential thermo-gravimetric analysis was performed on powders obtained by successive abrasion of the interface. The results show a good correlation between the mineral composition and the microstructure of the transition zone and its transport properties. It appears that the thickness of the transition zone, when the grout is young, is the main factor controlling transport properties, but that over the curing period, the mineral composition also becomes an important factor.