Effect of Molecular Weight of Polycarboxylate Superplasticizer on Its Dispersion, Adsorption, and Hydration of a Cementitious System

The aim of this study was to link the molecular weight (MW) of polycarboxylate superplasticizer (PCE) with the performance of cementitious system for the purpose of developing new products; PCE synthesized by copolymerization of methacrylic acid and methyl poly(ethylene oxide) methacrylate was characterized by proton nuclear magnetic resonance and gel permeation chromatography (GPC). The polycarboylate (PC) was separated into four fractions with different MWs using an ultrafiltration method. The interaction behaviors between PC fractions and cement particles were investigated by measuring the adsorption, zeta potential, and hydration. Results showed that PC fractions with medium MW showed a good dispersion and dispersion retention owing to the adsorption amount continuously increasing with time and delayed the longest cement hydration time. The highest MW of PC exhibited poor dispersion and dispersion retention, having the greatest adsorption amount on the cement surface and poor adsorption capacity in the later period, and carried out to promote hydration of cement compared with other polymers. It can be deduced that there was an ideal MW for the best different performance of the PC investigated. This can provide an important reference for optimizing the process parameters in the preparation.