Tricalcium silicate solid solutions

Woermann et al. (Wl) found that up to 1.4% of either Na20 or K2O could be incorporated into CjS at 1500°C and discussed mechanisms of substitution. 

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Toropov and Boikova [115, 116] have studied the solid solutions of tricalcium silicate with the rare earth silicates and yttrium as well as calcium germinates. Toropov stated that there are the substitutions 3Ca + 2Y, and in the stracture va-... 

Alite is a solid-solution series of trigonal, monoclinic, and triclinic modifications of impure tricalcium silicate, which is generally termed C S in the cement industry. Substitution of magnesium and aluminum for silicon causes triclinic pseudotrigonal forms to change to monoclinic pseudotrigonal forms other substitutions may involve iron and sodium. Alite may include up to approximately 4 percent impurity (Ghosh, 1983). It comprises 40 to 70 percent of normal portland cement clinker. Its density is 3.13 to 3.22 Mg/m. ... 

At the start of clinkering the material still contains substantial amounts of uncombined CaO as well as dicalcium silicate (C2S). In the presence of the liquid phase these compounds pass into solution the diffusion of the reactants is greatly facilitated in the liquid (as opposed to the solid state), tricalcium silicate (C3S) is formed in accordance with the following reaction and crystallizes ... 

The alkali in clinker is combined as a solid solution with the C3A phase. The crystalline stmcture changes from cubic to orthorhombic or monoclininc structure, depending on the content of Na in the C3A phase. Shin and Han studied the effect of different forms of tricalcium aluminate on the hydration of tricalcium silicate by applying DTA, TG, and conduction calorimetry. It was concluded that the hydration of tricalcium silicate is accelerated when orthorhombic, monoclinic, or melt C3A was present in the mixture. The cubic form of tricalcium aluminate was least effective for accelerating the hydration of the silicate phase. 

The hypothesis of the mechanism of healing is that the free calcium oxide in the cement and the calcium hydroxide liberated by the hydration of the tricalcium silicate of the cement, is carbonated by the carbon dioxide in the surrounding air and water. The carbon dioxide reacts with a solution of calcium hydroxide on the surfaces of the cracks. As the concentration of calcium hydroxide is reduced at the surfaces, more of it migrates from the interior of the material. Likewise, as the concentration of the soluble carbonates is reduced in the cracks, more diffuses in from the water phase. Calcium carbonate crystals precipitate and grow out from the surfaces of the cracks. The rate of diffusion of the carbonates is much greater into the cracks than into the solid, relatively nonporous cement paste. Therefore, the calcium carbonate crystals accumulate in the cracks... 

When the alumina-ferric oxide ratio is less than 0.64. a calcium aluminoferrite sohd solution (expressed as ss(C AF + C2F)) is formed Contents of this solid solution and of tricalcium silicate shall be calculated by the following formulas ... 

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