THE EFFECT OF MICA PARTICLES ON THE PROPERTIES OF COMPOSITES WITH A MATRIX OF GYPSUM-FREE PORTLAND-CEMENT .1.

Composites were prepared with a matrix of gypsum-free Portland cement, containing 2-10 wt. % of mica of various grain sizes and specific surfaces. The effect of mica was discussed in terms of the apparent viscosity of cement pastes, the time course of hydration reactions, the development of hydration heat, and compressive strengths. It was found that the different specific surface area of mica particles was capable of adsorbing various amounts of the aqueous solutions of the additives, thus markedly affecting the setting time and the apparent viscosity of the cement pastes. The phenomenon is also associated with the development of the heat of hydration which decreases with increasing mica content in the composite. All of the mica fractions tested decreased the compressive strengths of the composites prepared.