Lime (building and industrial material)

Types and basic chemistry

Common forms of lime include:

• Quicklime (CaO): produced by thermal decomposition of calcium carbonate; it is strongly alkaline and reacts vigorously with water.
• Slaked lime (Ca(OH)2): formed by adding water to quicklime; used in mortars, plasters and some water treatments.
• Hydraulic lime: a lime that sets under water or in damp conditions because it contains reactive silicates or aluminates; contrasted with non‑hydraulic (aerial) lime that sets by carbonation in air.

The principal chemical cycle begins with CaCO3 heated to yield CaO and carbon dioxide; adding water converts CaO to Ca(OH)2, and over time slaked lime partially reabsorbs CO2 from the air, reverting toward carbonate.

Production and properties

Production typically involves mining or quarrying of carbonate rock, followed by calcination in rotary kilns at high temperature. The temperature range used is sufficient to release carbon dioxide but varies with feedstock and kiln design. The resulting quicklime may be stored or transported in a dry form; slaking is carried out either at plant or on site to form a putty or dry powder. Lime materials are alkaline, corrosive when concentrated, and release significant heat during hydration.

Uses and applications

Lime has a wide set of applications across construction, agriculture and industry. In building trades it is an ingredient of mortar, renders, limewash and conservation mortars for heritage structures; it is also used with sand and pozzolans to make binders and as a component of older concrete formulations. Agricultural lime (commonly called agrilime) is spread on fields to reduce soil acidity and supply calcium. Industrial uses include water and sewage treatment, flue‑gas desulfurization, steelmaking as a flux, and chemical manufacture where lime is a feedstock for other calcium compounds. It also appears in paper making, sugar refining and glass production.

History and significance

Lime has been used for millennia: prehistoric lime mortars and plasters survive at many archaeological sites. Ancient builders exploited lime's binding and preservative properties; Roman engineers developed lime mortars and pozzolanic mixes that contributed to durable concrete works. Through history, lime also played roles in agriculture and metallurgy, and its industrial scale expanded with modern kilns and global construction demands.

Safety, environmental and notable distinctions

Quicklime is caustic and can cause severe chemical burns if it contacts skin or eyes; slaking is exothermic and must be controlled to avoid steam or splattering. From an environmental perspective, calcination emits carbon dioxide, although some CO2 is reabsorbed when lime carbonates during use and weathering. It is important to distinguish between the parent rock (e.g., limestone or chalk), quicklime (CaO), and slaked lime (Ca(OH)2), because each has different handling, reactivity and applications. For general discussions of calcium and related chemistry see resources on calcium.

Lime remains a fundamental, versatile material in both traditional crafts and modern industry, valued for its reactivity, alkalinity and ability to form durable mineral binders.