Influence of calcium sulphoaluminoferrite on the cement stone structure

Abstract

Usually to obtain expansive cements sulphoaluminate clinker or mix aluminate clinker with calcium sulphates (gypsum, hemihydrate, anhydrate) are used. This paper deals with the composition and properties of solid solution of calcium sulphoaluminoferrite. It was studied an influence of calcium sulphoaluminoferrite on structure and properties cement phases. For these cements ettringite is an important hydration product. The investigation of hydration and properties of sulphomineral cements shows that ettringite are formed thus providing expansion of cement stone. Study of the hydration processes of the calcium sulfoaluminoferrite mineral in gypsum solution showed that the hydration of fine mineral fractions (less than 28 μm) occurs during partial dissolution with crystallization of small ettringite crystals from solution. Sulphoaluminoferrite mineral is characterized by the growth of large prismatic ettringite crystals with their subsequent cleavage in fractions of 45–63 μm. Research showed that for expanding additives based on calcium sulfoaluminoferrite, a polyfraction composition combining only small fractions is preferable.

System "dispersed polyvinyl acetate-calcium silicate" in furnishing materials

“…It is of necessity to note that, an alternative process in the systems containing anhydrous mineral compounds of stable crystalline structure is viable for instance with silica, calcite and anhydrous wollastonite. Curve on the DTA charts shows that the compound based on wollastonite is characterised of an exoeffect at a temperature range of 320-650°C and maximum at 400 and 600 °C, thus corresponding to PVAD [16,17].…”