Effect of molecular weight of slow-release Polycarboxylate Superplasticizer on the properties of cementitious system

In order to improve the fluidity retention performance of cement, monomers containing ester groups were introduced into slow-release polycarboxylate superplasticisers (PCEs). Four slow-release PCEs with different molecular weights (M_w) were synthesised through aqueous free radical polymerisation. The effect of the molecular weight of slow-release PCEs on the dispersion performance, hydrolysis reaction ratio, adsorption process and hydration of cement was investigated systematically. Due to the hydrolysis reaction, the amount of adsorbed groups continued to increase over time. The adsorption amount of PCEs on the cement particles increased with increasing M_w, indicating that M_w was the main factor affecting adsorption. The retardation of cement hydration was weakened with increased M_w, due to a reduction in the number of molecules adsorbed on the surface of the cement particles. Among the four PCEs, the PCE with medium M_w displayed excellent initial dispersion. The PCE with the highest M_w exhibited the worst dispersion retention, the strongest adsorption capacity and the most cement hydration acceleration. The PCE with the lowest M_w showed outstanding dispersion retention and the maximum delay in cement hydration. According to fluidity retention requirements, an appropriate M_w may be thus selected, which provides a reference for the synthesis and performance of slow-release PCEs.