Reaction kinetics during early hydration of calcined phyllosilicates in model cement systems

Model cement systems form the basis for investigating the influence and behavior of three calcined phyllosilicates during early hydration. Metamuscovite acts as pure filler, accelerates alite hydration and leads to an increased degree of hydration of alite compared to the reference. A different picture emerges for metaillite and metakaolinite. They influence in addition the alite hydration which reaches at the onset of the aluminate clinker reaction as well as after 2 days of hydration significantly lower degrees of hydration. This indicates interaction of the negatively charged calcined clay surfaces with the sulfate from the pore solution. Chemical reactivity of the metaillite and metakaolinite during early hydration can be demonstrated by direct quantification as well as determination of portlandite consumption and C-S-H formation. This leads to a better understanding of the effect of individual calcined phyllosilicates and help to predict the influence of complex calcined clays on early hydration.