Design of the Ternary Gypsum-Based Building Composite Using Simplex Optimization

Abstract

The main disadvantage of gypsum as a building material is the loss of its mechanical properties in a wet environment and therefore the use of pure gypsum is limited only to the interior of buildings. The resistance of gypsum materials against moisture can be improved by the addition of any pozzolanic material and an activator of the pozzolanic reaction to the gypsum. The water-resistant CSH phases are formed by the reaction and the resulting gypsum-based materials evince better behaviour in a wet environment. Several ternary materials, composed of gypsum, lime, several types of pozzolans (silica fume, ground bricks, granulated blast-furnace slag) and silica sand were studied. The best resistance against water was achieved by the material containing silica fume, but its strength was lower than the strength of the other materials. Simplex optimization was used to design a composite with better mechanical properties. Maximum compressive strength was set as the goal of the optimization with regard to the fact, that silica fume is a relatively expensive material. After several steps, an optimized material with greater strength, containing reasonable amount of silica fume was designed.