Abstract:By using acrylamide(AM), N, N dimethylacrylamide(DMAA) and 2 acrylamido 2 methylpropane sulfonic acid(AMPS) as functional monomers to replace the monomer acrylic acid(AA) in polycarboxylate superplasticizers with different proportions, a series polycarboxylate(PC) superplasticizers with different functional groups were synthesized through radical polymerization. Molecular structures of the synthesized superplasticizers were characterized by FTIR. The influence of different functional groups on the main chain on the performance of PC superplasticizers was investigated by measurements of the spread diameters of fresh cement pastes with PC superplasticizers added, adsorption amount of PC superplasticizers on cement, zeta potential and hydration heat flow curves of cement pastes. The results show that, if the functional monomers of AM, DMAA or AMPS replace AA totally, the dispersion performance of synthesized PC superplasticizers is greatly reduced, and even is lost. The more negative charges in the PC superplasticizer molecules, the more superplasticizer molecules are adsorbed on the cement pastes. The contribution of —SO3-to adsorption capability is less than —COO- because of the complexation of —COO- with Ca2+. Carboxyl groups in PC molecules are the key factor for the retardation effect of PC superplasticizers on cement hydration.