Influence of sulfonate and phosphate groups in polycarboxylate ethers on properties of fly ash blended cementitious systems

Abstract

This investigation examines the effect of anionic monomer groups in polycarboxylate ether (PCE) superplasticizers on rheology, setting, compressive strength, and water absorption of cementitious systems containing fly ash additions. Five PCEs having the same backbone structure and different anionic groups are synthesized. The carboxylate functional group is replaced with 10 % or 30 % sulfonate or phosphate groups, while the total anionic monomer content, molecular weight, and side chain length are kept constant. Test results showed that the PCEs containing 30 % sulfonate or phosphate functional groups are effective in improving flow and reduce apparent viscosity, particularly in mixtures containing increased fly ash additions. Because of improved adsorption properties, setting times are extended, which consequently reduces the 1-day compressive strength when the carboxylates are gradually replaced by 10 % or 30 % sulfonate or phosphate functional groups. Yet, the late age strengths and water absorption are not affected by such replacements. Data reported in this paper can be of interest to admixture producers and concrete technologists seeking an efficient performance of PCE polymers in fly ash concrete mixtures.