Interfacial interaction between comb-like copolymer dispersants and tricalcium silicate

Abstract

Two commercial comb-like copolymer dispersants (also called polycarboxylate-based superplasticisers, hereinafter called PCs) were employed to investigate their interaction with tricalcium silicate (C3S). It is determined that when tricalcium silicate dissolves in deionised water, it releases a large amount of cations (mainly Ca2+). Those cations adsorb the surface of initially negatively charged tricalcium silicate and finally reach saturation. Through this mechanism, tricalcium silicate attains a slightly positive zeta potential. Thus, it is emphasised that with a larger amount of cations present in the synthetic pore solution, higher zeta potential values are measured. Owing to the positively charged layer of adsorbed cations, anionic PC adsorption occurs by chelating with calcium ions. Ultimately, the adsorbed PCs impart dispersity owing to its steric hindrance from hydrophilic graft side chains. Moreover, the introduced PCs lead to a strong retardation of tricalcium silicate hydration, and consequently have a significant effect on the initial dispersity of tricalcium silicate paste. Results are presented for a better understanding of the interaction between PCs and tricalcium silicate.