Zements

Zements, or cements, are hydraulic binders used to bind aggregates into concrete. The term often refers to Portland cement, the most common form. In everyday use, cement is ground to a fine powder and mixed with water to form a paste that hardens through hydration.

Most modern cements are produced by heating limestone (calcium carbonate) with clay or other materials to form clinker, then grinding clinker with gypsum. Portland cement accounts for the majority of cement produced worldwide. Other cements include blended cements containing fly ash, slag, or natural pozzolans to modify properties and reduce clinker content.

Standards specify composition and performance; common types include Portland cement, Portland-composite cement, and special cements like high-alumina or white cement. In Europe, EN 197-1 classifies cements by standard types; in the United States, ASTM C150 serves a similar role.

Hydraulic cements set and harden under water via hydration of calcium silicates and aluminates. Strength develops over days to weeks; curing and temperature influence performance and shrinkage. Cement mixes are used with aggregates and water to create concrete or with lime-based mortars for masonry.

Cements have roots in ancient binders, but modern Portland cement was developed in the 19th century, with a name linked to a visual likeness to Portland stone. The global cement industry remains energy-intensive, with ongoing efforts to reduce emissions through blended cements and supplementary cementitious materials.

Cement dust can be abrasive and alkaline, so proper personal protective equipment is advised. Cement should be stored dry, because exposure to moisture inside bags can begin premature setting.