Evaluation of the Dispersing Properties of Polycarboxylate-Type Superplasticizers with Different Molecular Weight in Cement Systems

In order to evaluate the dispersing properties of polycarboxylate-type superplasticizers (PCs) with different molecular weight in cement pastes, PCs with different molecular weight (low, medium, high) were synthesized, and used as superplasticizer for cement suspensions. The effect of molecular weight of PC on the zeta potential, adsorption, fluidity of the corresponding cement suspensions was investigated systematically, and total interparticle potential energy between particles was calculated. The results show that, the higher molecular weight of PC, the larger adsorption amount of PC. PC with medium molecular weight presents a better dispersing property than PC with high molecular weight, while PC with low molecular weight falls in between. The maintaining dispersing ability of PC for cement particles is weakened gradually with the increasing of molecular weight. The changing rule of total interparticle potential energy produced by PC is in accordance with the changing rule of dispersing property of PC in cement pastes. This indicates that the calculated results of total interparticle potential energy further support the explanation of dispersing property difference of PC in theory. This article uses the sum of electrostatic energy and steric hindrance potential as the total interparticle potential energy to evaluate the dispersing property of PC for the first time, which is meaningful for evaluation of dispersing property of polymer dispersant adsorbed on particle surfaces.