Experimental investigation of solute transport in unsaturated cement pastes

This article is dedicated to the development of a method for acquiring experimental data on ionic diffusion in partially saturated cement-based materials. A modified “half-cell” method is adopted in order to introduce the diffusing solute without disturbing the initial water content of the material. After a certain diffusion time (5 to 10 months), the concentration profiles of the tracer within the samples are measured by elemental mapping using the Laser Induced Breakdown Spectroscopy technique (LIBS). Analyses of the diffusion profiles obtained show a net decrease of the liquid-phase diffusivity with desaturation of the material, in accordance with the results in the literature. The innovation provided by this study consists in taking into account the adsorption of the tracer (Li) in the analytical processing of the diffusion profiles. This adsorption was quantified by measuring the interaction constant.