Ciment

Ciment, known in English as cement, is a binding material used in construction that sets, hardens, and adheres to other materials. The most widely used form is Portland cement, a hydraulic binder that hardens in the presence of water to form a solid matrix that holds aggregates together in concrete or mortar.

Portland cement is produced by grinding clinker—mainly calcium silicates such as alite (C3S) and belite (C2S)—with a small amount of gypsum. Clinker is formed by calcining limestone and clay or other silica- and alumina-rich materials in a high-temperature kiln. The ground product may be blended with supplementary cementitious materials such as fly ash or slag.

Production steps include quarrying and preparing raw materials, making a raw meal, calcination in a kiln at about 1,400–1,500 °C, and grinding the resulting clinker with gypsum to produce the final cement powder. Variants and performance additives tailor resistance to sulfate, heat of hydration, and setting time.

On mixing with water, cement hydrates to form calcium silicate hydrate and calcium hydroxide, generating strength through a chemical bond with aggregates. The setting process begins within hours and continues over days; proper curing is essential to reach intended strength and durability.

Common cement types include Portland cement and various specialty cements for specific conditions. Cement is primarily used to produce concrete, mortars, and stucco, sometimes in combination with admixtures or supplementary cementitious materials to modify workability, curing, or durability.

Environmental considerations include significant CO2 emissions from clinker production and high energy use. Efforts to reduce impact focus on improving energy efficiency, reducing clinker content, and substituting clinker with fly ash, slag, or natural pozzolans. The history traces from ancient lime-based cements to modern Portland cement, developed in the 19th century.