Retardation effect of styrene-acrylate copolymer latexes on cement hydration

Interactions between styrene-acrylate latexes and cement are investigated with emphasis of the charge properties of the polymer particles by means of calorimetry, adsorption measurement, and confocal laser scanning microscope. Three latexes with varied surface charges of polymer particles were prepared by respectively using methacrylic acid (MAA), sodium styrene sulfonate (SSS) and methyl poly(ethylene glycol) methacrylate (MPEGMA) as water soluble monomers during synthesis. It is found that the polymer latexes retard cement hydration in two manners, namely the delaying effect represented by a delayed hydration peak and the slowing down effect characterized by a reduced main hydration peak during the acceleration period. The delaying effect is closely related to the concentration of carboxylic groups existing in the latex, while the depression effect of hydration rate is majorly caused by the adsorption of polymer particles on surface of cement grains and proportional to the total charge density of polymer particles.