Title: An Approach to the Rheological Behavior of Cementitious Systems Blended with Calcined Clays and Superplasticizers
Author(s): Ricarda Sposito, Marlene Schmid, Johann Plank and Karl-Christian Thienel
Publication: Symposium Paper
Appears on pages(s): 659-685
Keywords: calcined clays, superplasticizers, rheology, viscosity, workability
Calcined clays represent a promising future supplementary cementitious material (SCM) because of the worldwide availability of suitable clays and low material-related CO2 emissions during calcination. The application of superplasticizers is inevitable for a secured workability of cementitious systems with calcined clays due to their specific chemophysical properties. For their prospective use as SCM, a sound knowledge is elementary about the interaction of calcined clays with superplasticizers depending on clay and polymer structure. An ordinary Portland cement is replaced by 20 wt% of calcined clays. Four different calcined materials are used: one calcined clay mixture, industrial metakaolin, a metaillite and a metamuscovite. One polycondensate and one polycarboxylate-based polymer, both industrial products, are chosen as superplasticizers. The required dosages are adjusted by the same slump flow, so a similar dispersing behavior for all systems is given immediately after water addition. Over a period of two hours after water addition, the rheological behavior is evaluated via mini slump test and by rotational viscometer. The impact of different velocities during measurements with the viscometer provides further information related to the viscosity of these systems.