Portland cement is the most common type of cement in general use around the world as a basic ingredient of concrete, mortar, stucco, and non-specialty grout. Hydraulic cements (such as Portland cement) are made of a mixture of silicates and oxides, the four main mineral phases of the clinker, abbreviated in the cement chemist notation, being:  C3S: alite (3CaO·SiO2);  C2S: belite (2CaO·SiO2); C3A: tricalcium aluminate (3CaO·Al2O3) (historically, and still occasionally, called celite); C4AF: brownmillerite (4CaO·Al2O3·Fe2O3). Hydraulic cement set and become adhesive through a chemical reaction between the dry ingredients and water. The chemical reaction results in mineral hydrates that are not very water-soluble and so are quite durable in water and safe from chemical attack.