Clinker is the primary active ingredient in cement, produced by sintering limestone (calcium carbonate) and clay (alumino-silicate) at temperatures up to 1450 °C. This process causes the raw materials to chemically react to form new compounds, primarily tricalcium silicate, dicalcium silicate, tricalcium aluminate, and tetracalcium aluminoferrite. These compounds are responsible for the hydration and setting characteristics of cement. When mixed with water, these silicates and aluminates hydrate to form calcium-silicate-hydrates (C-S-H) and calcium-aluminate-hydrates, which are the principal compounds contributing to the strength and durability of hardened concrete.