Organic and inorganic reactions in polyacrylate modified cement mortars

The microstructure forming process of polyacrylate (PA) latex modified mortars was investigated from mixing to hardening, with specific emphasis on the organic and inorganic reactions between polymer and cement hydration products. An improved four-step model was proposed to clarify the mechanism of polymer modification in view of the reactivity of organic polymer latex in inorganic cement-based materials. And the influence of PA latex on the microstructure formation of mortars was revealed through an analysis of pore structure and polymer distribution. Owing to organic and inorganic reactions, polyacrylate polymer will not disperse uniformly in fresh mortar, and polymer particles will deposit on cement particles and flocculate into big groups at some local areas in mortars. The modification of polyacrylate polymer on cement-based materials is localized which can be stated as the localization of polymer modification. The addition of PA latex will also introduce some air voids into the mortars due to the chemical reaction between its surfactant and cement hydrates. This is important for the physical and mechanical properties improvement because a kind of purposefully designed polymer latex will effectively enhance the performance of cement-based materials in a relative small dosage, which means cutting the cost down and broadening its application.