Calcined clays represent a promising supplementary cementitious material (SCM) to face the growing demand for binders and to compensate the decreasing availability of established SCM worldwide. A fundamental knowledge about the interaction with superplasticisers is required for their optimized use as clinker substitute. As clays contain different phyllosilicates, this study focus on the behaviour of calcined phyllosilicates (metakaolin, metamuscovite, metaillite) and one practically relevant calcined naturally occurring clay. On blended cement pastes, the impact on rheology, hydration and setting behaviour with two polycarboxylate-based superplasticisers (PCE) is investigated by rotational viscometer, isothermal calorimetry and ultrasound, respectively. The examinations reveal a good dispersion effectiveness of both PCE even with challenging calcined phyllosilicates. The demand for superplasticiser can be derived largely from physical properties of calcined materials, except for metamuscovite. The calcined naturally occurring clay is easily dispersed due to its high quartz content. The physical properties are also key parameter for the hydration and setting: high specific surface area and pozzolanic properties of calcined phyllosilicates can compensate retardation effects whereas there can be a significant retardation due to superplasticiser overdosage. Calcined clays with quartz can represent a promising future clinker substitute for concrete industry with regard to uncritical superplasticiser dosages    «

Calcined clays represent a promising supplementary cementitious material (SCM) to face the growing demand for binders and to compensate the decreasing availability of established SCM worldwide. A fundamental knowledge about the interaction with superplasticisers is required for their optimized use as clinker substitute. As clays contain different phyllosilicates, this study focus on the behaviour of calcined phyllosilicates (metakaolin, metamuscovite, metaillite) and one practically relevant cal...    »