Synthesis of modified polycarboxylate superplasticiser and its effect on cement properties

Abstract

A polyether, acrylic acid and oleic acid were used as raw materials to synthesise oleic acid modified polycarboxylate superplasticiser (OA-PCE) by emulsion polymerisation. The synthesis process was optimised using orthogonal experiments. The colloidal interfacial chemistry results showed that the OA-PCE was more capable of reducing the surface tension of aqueous solutions than an unmodified traditional polycarboxylate superplasticiser (JS-PCE) and its adsorption capacity on cement particles was greater. The isothermal adsorption behaviour of the two kinds of PCEs on cement conformed to the Freundlich isothermal adsorption equation; it was a physical adsorption process by electrostatic action. The effect of OA-PCE dosage on the flowability of cement slurry was preliminarily investigated by rheological behaviour tests. According to the yield stress, plastic viscosity and thixotropic ring area of the slurry, a dosage of 0.35 wt% OA-PCE produced the optimum effect. The compressive strength of concrete made with 0.35 wt% OA-PCE at 4 h and 7 days was, respectively, 117.1% and 88.3% higher than that of the control group and met the standards for the use of concrete in metro pipe sheets. OA-PCE synthesised by emulsion polymerisation is therefore significant for the development of PCEs both in terms of the polymerisation method and practical applications.