Vapour multicycle sorption of a cement–bentonite cutoff wall material: Hysteresis Effects

This paper examines the effects of multicycles of desorption/adsorption on the water isotherms of a typical cement–bentonite mixture. These water isotherms were evaluated over a relative humidity (RH) range of 90% and 0.3%. This study shows that, after the first adsorption–desorption cycle, the subsequent cycle shifted the water isotherm curves upward, particularly at RH < 70%, with a high degree of hysteresis. In contrast, at RH > 70%, the water isotherm curves shifted slightly downward with a low degree of hysteresis. The overall degree of hysteresis slightly decreased with the subsequent cycles. It is postulated that multi-adsorption–desorption cycles led to microstructural changes in the CB porous system as the CB material’s water retention ability was enhanced by increasing isotherm cycles.