Effects of the charge density of anionic copolymers on the properties of fresh cement pastes

[Display omitted] •Effects of charge density of anionic polymers on properties of cement were studied.•Polymers with different charge densities but similar molecular weights were prepared.•The adsorption, fluidity, bleeding and rheology were tested.•The polymer with medium charge density effects on the cement paste strongest.•The study indicates the action mechanism of anionic polymers in cement pastes. In this work, the effects of the charge density of the anionic copolymers on the properties of fresh cement pastes were fully discussed. A series of random copolymers based on anionic acrylic acid (AA) and nonionic N, N-dimethyl acrylamide (DMAA) were prepared by free radical solution polymerization. By varying the initiator concentration, the obtained polymers have different charge densities but similar molecular weights. The adsorption, fluidity, bleeding and rheology of the cement pastes mixed with different polymers were tested, respectively. The results indicate that the anionic and nonionic monomer of the polymers effect on the properties of fresh cement paste cooperatively, and the polymer with medium charge density can effect on the cement paste strongest. Our study is quite beneficial to understand the structure–property relationships and action mechanism of anionic polymers in cement pastes.