Correlation between the adsorption behavior of colloidal polymer particles and the yield stress of fresh cement pastes

Abstract

Correlation between adsorption behavior of colloidal polymers on cement grains and yield stress of fresh cement pastes (fcps) is studied using four polymer latexes with varied surface charge density and glass transition temperature (Tg). Adsorption isotherm of the polymers is divided into two stages: before and after adsorption plateau. Higher charge density and lower Tg are beneficial to adsorption of polymer on cement grains. Before adsorption plateau, the adsorbed polymer particles play a bridging effect among cement grains which firstly increases and then decreases with increasing surface coverage ratio. Maximum bridging effect occurs at surface coverage ratio of ca. 20%. After adsorption plateau, yield stress of the fcps is significantly lower than that of the blank fcp because the adsorbed polymer layer reduces interaction force between cement grains, by increasing the minimum distance between two cement grains and generating repulsive force due to negative charges of the polymer particles.