Effects of poly(ethylene glycol) branch chain linkage mode on polycarboxylate superplasticizer performance

Polycarboxylate superplasticizers (PCs) with ether linkages and ester linkages between the main chains and the poly(ethylene glycol) (PEG) branch chains were synthesized, respectively. The effects of the PCs molecule linkage mode on the performance of concrete paste were investigated using the slump loss test and thermogravimetric analysis and analyzing fluidity, absorption, and setting time. Results showed that the linkage between main chains and PEG branch chains in PCs molecules had an important influence on the performance of cement paste and concrete prepared from them. PCs with ester linkages can endow the cement paste with higher fluidity and higher water-reduction ratio resulting from the higher absorption amount on the cement particles. This is related with the alternating distribution of the carboxyl groups and branch chains of PEG when different macromonomers are involved in the preparation of PCs. PCs containing ester linkages are more vulnerable than PCs with ether linkages in an alkali environment, leading to quicker slump loss and shorter setting times. In contrast, PCs with ether linkages had excellent fluidity and slump flow stability. A slightly different ettringite hydration product was observed during the early period of the hydration of cement paste that employed these two PCs. Copyright (c) 2012 John Wiley & Sons, Ltd.