Effect of polycarboxylate superplasticizer on the hydration of cubic C3A: Interaction with sulfate ions and correlation to molecular structure

Effect of polycarboxylate superplasticizer (PCE) on cubic C 3 A's (cub-C 3 A) hydration was investigated by using calorimetry, TOC analysis, ICP-OES, etc. With the increased acid-to-ether ratio (A/E) of PCE, a first acceleration and then retardation effect on cub-C 3 A's hydration is found, which is caused by the competitive adsorption between PCE and Ca-Ŝ ion pairs and the correspondingly different effects on cub-C 3 A's dissolution. The increased A/E enhances PCE's adsorption amount. However, PCE's adsorption could either promote or retard cub-C 3 A's hydration depending on PCE's molecular structure. Specifically, PCE with an A/E of 2 could hinder the adsorption of Ca-Ŝ but does not effectively block cub-C 3 A's dissolution as that of Ca-Ŝ ion pairs due to the formed loose adsorption layer. The A/E of 6 further decreases the adsorption of Ca-Ŝ ion pairs and accelerates cub-C 3 A's hydration. Along with the further increased A/E, a compact adsorption layer can be formed, which could hinder cub-C 3 A's dissolution and retard its hydration.