Effects of two oppositely charged colloidal polymers on cement hydration

Effects of two styrene acrylate copolymer latexes with opposite charge properties on cement hydration were investigated by calorimetry, in-situ XRD and pore solution analysis. It is found that the anionic latex (AL) shows much stronger retardation effect than the cationic latex (CL) on OPC hydration, which should be caused by higher adsorption affinity of AL. Specifically, for aluminate reaction during OPC hydration, the strong adsorption of AL on positively charged C(3)A surface inhibits C(3)A dissolution and AFt formation, which invalidates the dependency of the secondary C(3)A dissolution on the sulfate depletion in normal OPC hydration. For the silicate reactions, mainly C3S hydration, AL again exhibits much higher adsorption on C3S and consequently stronger retardation than CL, which is caused by the reversal of charging property of C3S grains from negative in pure water to positive in Ca2+ rich solution. The adsorbed polymer may severely block nucleation sites for C-S-H precipitation.