cements

Cements are finely ground powders that act as binding agents in construction. The most widely used type is Portland cement, which forms a paste when mixed with water and hardens to bind aggregates into concrete or to create mortars in masonry.

Portland cement is produced by calcining limestone and other materials to form clinker, which is then ground to a fine powder and blended with small amounts of gypsum to control setting. The process is energy-intensive and involves high-temperature kilns.

In addition to Portland cement, many hydraulic and blended cements exist. These include slag or fly ash blended cements, pozzolanic cements, and specialized cements such as rapid-hardening or sulfate-resisting varieties. Lime-based cements are non-hydraulic alternatives used in historic restoration.

Cement is most commonly used in concrete, where it binds coarse and fine aggregates, and in mortars for masonry joints. When mixed with water, cement hydrates and gains strength through a sequence of chemical reactions that develop over hours to days.

Properties such as strength development, workability, heat of hydration, and durability influence mix design. Cement types and concrete mixes are specified by national or international standards to ensure performance in structures. Proper curing is essential to minimize cracking and shrinkage.

Cement production emits significant quantities of carbon dioxide, primarily from calcination and fuel combustion. Efforts to reduce impact include using alternative fuels, improving energy efficiency, and substituting clinker with supplementary cementitious materials such as fly ash, slag, or natural pozzolans.