A study on the interactions between polycarboxylate ether superplasticizer and montmorillonite

The adsorption of polycarboxylate ether (PCE) superplasticizer on the surface of cementitious materials is a prerequisite for its dispersion and water reduction capability. This paper investigated the adsorption isotherms and kinetics of PCE on montmorillonite (MMT) at 278, 288, 298, and 308 K, respectively. Based on the adsorption behaviors, the critical intercalation concentration of PCE was estimated, and the characterizations of surface adsorption and intercalation were examined. Results show that when its concentration is <0.9 mg/mL, PCE is mainly adsorbed on the surface of MMT. The galleries of MMT are intercalated by the side chain of PCE completely at a concentration of 10 mg/mL. The adsorption isotherms and kinetics of PCE on MMT follow the Freundlich isotherm equation and the pseudo-second-order adsorption equation, respectively. The surface adsorption of PCE is not affected by the temperature, but it presents a lower adsorption saturation at a higher temperature. PCE shows a monolayer thickness of 5.63 nm on the surface, but intercalation conforms to multi-layer adsorption.