Cement is normally made of Calcium aluminate which are from Limestone and Bauxite. The active ingredients are mono-calcium aluminate (CaAl2O4) and mayenite (Ca12Al14O33).
Strength forms by hydration to calcium aluminate hydrates. They are well-adapted for use in refractory (high-temperature resistant) concretes, e.g. for furnace linings. ===== Note the term hydraulic - it means water is required as a chemical reaction occurs where the ingredient molecules react with water to form hydrates. Notice that the ingredients contain no water molecules and no hydrogen atoms. And from another article : Cement sets when mixed with water by way of a complex series of chemical reactions still only partly understood. The different constituents slowly crystallise and the interlocking of their crystals gives cement its strength. So you will have to research various theories, I don't have any more information.
