This document discusses the composition and hydration process of ordinary Portland cement. It begins by outlining the major components of cement and the physical and chemical processes involved in hydration. The key points are: - Cement is produced by burning limestone, clay, and other materials at high temperatures, forming clinker which is then ground with gypsum. - The main compounds in cement are tricalcium silicate, dicalcium silicate, tricalcium aluminate, and tetracalcium aluminoferrite. - Hydration involves physical and chemical changes as the cement sets and hardens over time. Hydration produces heat and results in a solid material. - Gy