Influence of Acid/Ether-Ratio on Composition and Dispersive Property of Polycarboxylic Type Water Reducers

Abstract

Polycarboxylic type water reducers were synthesized at different molar ratios of acrylic acid to methyl-allyl polyethylene glycol2400 (acid/ether-ratio). Influence of the acid/ether ratio on its composition and dispersive property were studied by means of Gel Permeation in Chromatography (GPC) and fluidity test of cement paste. The GPC analysis results showed that the average molecular weight and polydispersity were increased with the increase of acid/ether-ratio, but the polymerization degree should be no longer increased as which reached to a certain value, the excessive small-monomers would be self-polymerized when macro-monomers had been consumed. As the final product of polymer at an acid/ether ratio of 5:1, was composed of un-reacting macro monomer (about 6%) and the copolymer of water reducers (about 92%) and the copolymer of small monomers (about 2%). The result of fluidity of cement paste showed that the acid/ether-ratio also influenced the dispersive property to different cement, its ability would be bad if at the ratio of 2:1, then the property of dispersive and fluidity retaining should be all well if at 3.5:1, and the beginning dispersive ability might be high but the ability of fluidity retaining be low as the ratio was beyond 4.5:1.