Reactive forms of dicalcium silicate and belite cements

Reactive forms of dicalcium silicate and belite cements 51... 

Owing to the lower reactivity of belite, the overall rate of hydration, and along with it the strength development up to about 90-180 days, is slowed down with increasing belite and decreasing alite contents in the cement (Bei and Ludwig, 1990). At the same time the final strength of a Portland cement with an elevated C2S content may exceed that of an ordinary Portland cement, because more C-S-H and less portlandite is formed in the hydration of dicalcium than of tricalcium silicate. 

Another dopant that may be considered for increasing the reactivity of belite cements is S04 ions (Gies and Knofel, 1987 Stark et al, 1987). Under these conditions the final clinker contains the rather than the a -CjS phase, even if high cooling rates have been employed however, the SO -doped form of yff-dicalcium silicate is much more reactive than its SO -free counterpart. The doped C S typically contains about 3% each of SO3 and AI2O3 in its crystalline lattice. If an SO3-doped belitic clinker that also contains some alite is to be produced, the amoimt of SO3 in the raw meal must not exceed... 

Kuznetsova et al. (1992) produced activated belite cements by introducing into the raw meal industrial waste products containing phosphoras, chromium, and titaniiun, and by employing cooling rates of up to 5000 K/min, Such clinkers contained dicalcium silicate mainly in its form, but a and a modifications were also present. By adding carbon to the raw mix, regions with local temperatures above 2100 °C were obtained before the bulk of limestone present was decarbonated. This resulted in a non-stoi-chiometry of the produced clinker minerals and along with it an increase of reactivity. 

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