Physical retardation mechanism of latex polymer on the early hydration of cement

The physical retardation effects of styrene/butyl acrylate copolymer latex on the early hydration of cement were investigated, with emphasis of the deformation of polymer particles adsorbed on cement. Five latexes with different glass transition temperatures were prepared by changing the soft monomer (butyl acrylate) content. The diameter of the polymer particles in colloidal solution was studied by dynamic light scattering and the diameter of the polymer particles adsorbed on cement was observed by environmental scanning electron microscopy. It was found that the diameters of polymer particles adsorbed on cement were larger than those in colloidal solution, especially for polymer particles with a high content of soft monomer. The ‘real coverage area’ of polymer particles on cement was theoretically calculated according to the number average diameter of polymer particles adsorbed on cement. It was found that, instead of the adsorption amount of polymer on cement, the real coverage area of polymer on cement is positively correlated with the setting time of latex-modified cement paste. A higher content of soft monomer led to easier deformation of the polymer particles adsorbed on cement, so that the retardation effect of latex on the early hydration of cement increased.