Showing papers in "Journal of The Chemical Society (resumed) in 1950"

726. Hydrated calcium silicates. Part I. Compound formation at ordinary temperatures

Abstract: Hydrous calcium silicates prepared at room temperature appear amorphous, but X-ray photographs show that compounds are formed having a considerable degree of crystalline character. Essentially the same product, calcium silicate hydrate (I), can be obtained by the action of water on tricalcium silicate, by double decomposition of calcium nitrate and sodium silicate, or by reaction of calcium hydroxide solution with silica gel, although crystallization is more marked in the first case. The phase relationships between solid and solution have been investigated and are sufficiently reproducible to suggest that the results represent a fair approximation to equilibrium conditions. A second phase, calcium silicate hydrate (II), with a composition in the neighborhood of 2CaO,SiOaq and X-ray pattern differing only slightly from the above, has been obtained by decomposition of tricalcium silicate and probably exists in equilibrium with calcium hydroxide solutions containing over I-13 g/1 of CaO. A tentative interpretation of the x-ray data of calcium silicate hydrate (I) suggest a layer structure, possibly showing some similarities to the clay minerals.