Interaction between polycarboxylate superplasticizers and non-calcined clays and calcined clays: A review

At first, a critical overview of current polycarboxylate (PCE) technology including the chemistry of different kinds of PCEs, characteristic molecular properties, their interaction with cement and application aspects are discussed. In the following, the classification and chemistry of clays and clay minerals is presented. In addition, the interaction of PCE superplasticizers with clay minerals and in particular the very harmful chemical sorption of PCE by montmorillonite (MMT) clay which causes a substantial reduction or even complete loss of PCE dispersing effectiveness are introduced. Possible mitigation strategies from the open literature to remedy the negative effects of clay are outlined. Over the last years, calcined clays have gained substantial attention as supplementary cementitious material (SCM). This paper also covers their chemistry and properties as well as their different interaction mode with PCE superplasticizers. Finally, future concepts in PCE technology regarding enhanced clay tolerance and enhancement of the fluidity of Limestone-Calcined Clay Cement (LC3) are proposed.