Influences of PCE superplasticizers with varied architectures on the formation and morphology of calcium hydroxide crystals

Abstract The impact of polycarboxylate (PCE) superplasticizers on calcium hydroxide (CH) precipitation and morphology were studied aiming at further understanding retardation effect of PCEs on cement hydration. Three comb-like PCEs with varied architecture and two linear copolymers (PAS) charged by carboxylic and sulfonic groups were synthesized. CH precipitate was prepared by simultaneous feeding NaOH and CaCl2 solutions in bulk solution containing various polymers. Analytical techniques of solution conductivity, ICP−OES, TG, XRD and SEM were used. Results show that the required [Ca] for massive CH precipitation is greatly increased by the presence of the polymers, suggesting inhibited nucleation and growth of CH crystals. The large incorporation of the polymers remarkably reduces the crystal size and consequently increases the specific surface area of the obtained CH. The polymers with higher density of carboxylic groups present stronger impacts on CH precipitation while such effect of the solely sulfonic group charged PAS is negligible.