A review of cement-superplasticizer interactions and their models

This paper presents a focused review of cement-superplasticizer interaction s. It has been concluded from the survey of the literature that cement-supe rplasticizer interactions are generally preceded by the adsorption of super plasticizers on the hydrating cement particles. However the mechanisms of s uch adsorptive interactions have not been adequately addressed experimental ly or discussed in the literature. The reason for this appears to be the la ck of a conceptual model that can delineate the results to date and project needed experiments. A charge-controlled-reaction mechanism model involving Ca2+ ions from initial hydration is proposed to explain the adsorption cha racteristics of superplasticizers and other organic additives and their eff ects. The calcium ions released by hydration form a bilayer immediately upo n contact of water with the cement, which is followed by adsorption of supe rplastizer anions on the Ca2+ ion side of the bilayer. The interfacial stru ctures and their influence on electrical characteristics, hydration reactio ns and phase growth in the hydrating cement are discussed in terms of the p roposed model.