Influences of Star-Shaped Polycarboxylate Superplasticizers with Different Arm Lengths on Their Performances in Cement Paste

摘要

A series of star-shaped polycarboxylate superplasticizers (SPCEs) possessing different arm lengths were synthesized by changing the amount of chain transfer agent in the polymerization stage. The molecular structure information was determined by ~1H Nuclear Magnetic Resonance (~lH NMR) and gel permeation chromatography (GPC). The effects of arm length on the adsorption behavior in cement pastes, and the rheological properties, zeta potential and hydration heat of cement pastes were also evaluated. SPCE with moderate arm length exhibited prominent dispersing capacity, low surface tension, strong adsorption; the arm length was directly proportional to hydration delay and reduction. Furthermore, the moderate arm length exactly corresponded to strong hydrophilicity, suggesting that the high-performance superplasticizer was designed towards as hydro-philic as possible. The aim of this study is to provide a theoretical guidance from viewpoint of surface-interface physicochemistry in designing a superplasticizer with great potential applications in concrete engineering requiring good workability and other performances.