Calcined gypsum–lime–metakaolin binders: Design of optimal composition

Abstract

The effect of composition on the properties of calcined gypsum–lime–metakaolin pastes is investigated. The components in the calcined gypsum–lime–metakaolin–water system are found to interact synergically; there is no simple way to find the optimum composition. Therefore, an optimization is performed using the sequential simplex method which leads very fast to a significant enhancement of mechanical properties. Already after the first trial the compressive strength is almost two times higher than for the most successful initial mixes designed in a common way without optimization and more than three times higher than for the reference calcined gypsum–lime paste. The bending strength and dynamic modulus of elasticity exhibit similar improvements. In addition, the better mechanical properties are achieved without any negative effect on thermal conductivity and water vapor diffusion coefficient.