Effects of the chemical structure on the properties of polycarboxylate-type superplasticizer

Based on the analysis of the chemical structure of polycarboxylate-type sup erplasticizers with polyoxyethylene (PEO) side chains, the dispersing prope rties for cement particles were investigated. Analyzed characteristics were the PEO side chain length, the degree of backbone polymerization, the comp osition of functional groups such as carboxylic and sulfonic groups, and th e purity of polymers. Their relative effectiveness as dispersants was evalu ated in cement paste by measuring paste flow, plastic viscosity, and shear yield stress at different water/cement ratios (w/c). Although the effects o f chemical structure on the paste fluidity were not significant at high w/c , they became significant at w/c below 25%. Polymers with longer PEO side c hains, lower degrees of backbone polymerization, and higher contents of sul fonic groups showed higher dispersing power. Higher concentrations of ionic functional groups in the aqueous phase delayed the setting of cement paste . (C) 2000 Elsevier Science Ltd. All rights reserved.