Dicalcium silicate structures

Common (dry) cement consists of anhydrous crystalline calcium silicates (the major ones being tricalcium silicate, CasSiOs, and (3-dicalcium silicate, Ca2Si04), lime (CaO, 60%), and alumina (a complex aluminum silicate, 5%). While cement is widely used and has been studied in good detail, its structure and the process whereby it is formed are not completely known. This is due to at least two factors. First, its three-dimensional arrangement of various... 

The conclusion is that both the body structure and the surface structure of tobermorite are highly reproducible. Whether we use tricalcium silicate or fi-dicalcium silicate as starting solids, whether we use a water to solid ratio of 0.7 or 9.0, whether we use paste hydration or ball-mill hydration or a third type which I have not discussed (which gave the six other points on the curve), we wind up with a tobermorite having very nearly the same body structure and surface structure. 

Yang, S., and Song, H. (1992) The structure and properties of hydration of doped dicalcium silicate, in Proceedings 9th ICCC, New Delhi, Vol. 4, pp. 291-296. 

Barbier J, Hyde BG (1985) The structures of the polymorphs of dicalcium silicate, Ca2Si04. Acta Cryst B 41 383-390... 

The difference in hydraulic activity of dicalcium silicates arises as a result of the difference in stability of inherent crystal structure. The usual form of dicalcium silicate in Ordinary Portland Cement (OPC) is p-CjS, which reacts more slowly with water and results in the lowest rate of heat... 

The mechanism of Si-O chemical bonding was analyzed for covalent and ionic bond orders in p- and Y-C2S. Each bond order was evaluated by an overlapping population calculated by the DV-Xa molecular orbital method (Xiuji et al. 1994). There are slight differences in computed covalent and ionic bond orders obtained for both dicalcium silicates. However, Xiuji et al. (1994) demonstrated that the differences in hydraulic activity between p- and Y-C2S do not arise from the difference of Si-O chemical bonding. Further investigation will be required to establish the relationship between these differences in the crystal structure to hydraulic activity of belite. 

Odler, I., and Skalny, J., Pore Structure of Hydrated Calcium Silicates. 11-Influence of Calcium Chloride on the Pore Structure of j8-Dicalcium Silicate, J. Colld. Int. ScL, 36 293-297 (1971)... 

Kantro, D. L., Weise, C. H., and Brunauer, S., Paste Hydration of B-Dicalcium Silicate, Tricalcium Silicate and Alite, Symp. Structure of Portland Cement Paste and Concrete, pp. 309-327, Highway Res. Board (1966)... 

Portland cement clinker. In addition to the major dicalcium silicate and tricalcium silicate phases, the structure shows silicate and tricalcium silicate phases, smaller amounts of tricalcium aluminate (3Ca0-Al203), and millerite (4Ca0-Al203-Fe203). On reaction with water, the clinker forms a complex hydrated product. This product is the cementitious material. It is a noncrystalline calcium silicate gel resulting from the tricalcium silicate and dicalcium silicate. The microstructure of set cement is shown in Figure 11.25. 

Mumme, W. G., L. Cranswick and B. Chakoumakos (1996). Rietveld Crystal Structure Refinement from High Temperature Neutron Powder Diffraction Data for the Polymorphs of Dicalcium Silicate . Neues Jahrbuch Fuer Mineralogie - Abhandlungen 170 (2) 171-188. 

Richardson, I. G. 2004. Tobermorite/jennite- and tobermorite/calcium hydroxide-based models for the structure of C-S-H applicability to hardened pastes of tricalcium silicate, p-dicalcium silicate, Portland cement, and blends of Portland cement with blast-furnace slag, metakaolin, or silica fume . Cement and Concrete Research 34 (9) 1733-1777. 

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