Properties of Polycarboxylate Superplasticizers with Different Molecular Structure: A Comparative Study

Abstract

Polycarboxylate superplasticizers (PCEs) with different molecular structure had been synthesized and characterized by FT-IR. PCEs were mainly included polyester (Type A), polyether (Type B) and ester ether copolymer (Type C). The application properties, adsorption behaviors and hydration process were investigated. The TOC was used to measure the adsorption amount, and crystal components in the hydration products were detected by XRD analysis. Test showed that Type B had the excellent performance, including large water reduction rate and strong adsorption capacity. The ester group in the molecular structure of Type A and C could improve the fluidity retention of cement paste, but the hydrolysis of ester group also weakened adsorption capacity on cement particles. In addition, in the cement-water-PCEs system, the difference of molecular structure would affect the early hydration process of cement slurry. For example, research indicated that the main hydration peak and maximum elevated temperature was delayed by adding PCEs. Through the examination of hydration products, it revealed that the intensity of calcium hydroxide (CH) and ettringite (AFt) peaks with Type B was higher than the other. The concrete application performance results indicated that PCEs had the basically equal contribution to the compressive strength. Keywords molecular structure; ester group; adsorption; hydration products; compressive strength