Experimental Study of the Water Desorption and Drying Shrinkage of Cement-Based Materials with Thin Slices

Abstract

The aim of the present study is to experimentally investigate the water vapor desorption and drying shrinkage of cement-based materials during a step-by-step desorption process, with the objective to link drying shrinkage to water desorption. Water vapor desorption isotherms of two cement pastes and two mortars (with water-to-cement ratio of 0.5 and 0.8) were studied using thin slices with three thicknesses 1 mm, 2 mm and 3 mm. Drying shrinkage was measured with 2 mm slices for each material. The slice thickness has an impact on the relative mass variation, but the difference between 2 mm slices and 3 mm slices is very small or even negligible. The results obtained in the present study are compared with a former study on larger prismatic beams. The curing condition influences the water desorption isotherm: the water content in the present study is always higher at each relative humidity after a longer curing period with thin slices. The size effect is pronounced for drying shrinkage: the drying shrinkage obtained with slices is always bigger than larger prismatic beams. The correlation between drying shrinkage and water mass loss shows two almost linear parts with different slopes for both cement pastes and exhibits three characteristic phases for both mortars.