Abstract:Polymeric superplasticizers with varied hydrophobicity were synthesized by copolymerizing acrylic acid, methyl polyethylene glycol methacrylate and styrene through free radical polymerization. The water solubility of the synthesized polymers was adjusted by changing the copolymerization ratio of hydrophilic and hydrophobic monomers. It is found that the synthesized polymers change from water soluble to insoluble and form nano particle dispersions when the proportion of styrene monomer is above 50%. The particle size of the nano particle dispersion increases with increase of the styrene proportion. The mini cone tests were conducted to evaluate the dispersing capability of the polymer nano particles in cement pastes. It is shown that the prepared polymer nano particles can effectively enhance the fluidity of fresh cement pastes. The fluidity of fresh cement pastes by addition of nano particle dispersion shows good retention and even increases with elapsed time, indicating that the nano particle dispersion bears so called slow releasing effect in fluidity retention of fresh cement pastes. Isothermal calorimetry was employed to study the effect of polymer nano particles on cement hydration. It is found that addition of polymer nano particles in the fresh cement pastes causes retardation effect but to a lesser degree than the widely used polycarboxylate superplasticizers.
