Lime (material)

Calcium oxide can occur as a product of coal-seam fires and in altered limestone xenoliths in volcanic ejecta.

[1] The International Mineralogical Association recognizes lime as a mineral with the chemical formula of CaO.

[2] The word lime originates with its earliest use as building mortar and has the sense of sticking or adhering.

The rocks and minerals from which these materials are derived, typically limestone or chalk, are composed primarily of calcium carbonate.

In the lime industry, limestone is a general term for rocks that contain 80% or more of calcium or magnesium carbonate, including marble, chalk, oolite, and marl.

Further classification is done by composition as high calcium, argillaceous (clayey), silicious, conglomerate, magnesian, dolomite, and other limestones.

[5] Uncommon sources of lime include coral, sea shells, calcite and ankerite.

In wet slaking, a slight excess of water is added to hydrate the quicklime to a form referred to as lime putty.

Lime is commonly used as a binding mortar in masonry due to its adhesive properties with bricks and stones.

An example is when slaked lime (calcium hydroxide) is mixed into a thick slurry with sand and water to form mortar for building purposes.

Lime has many complex qualities as a building product including workability which includes cohesion, adhesion, air content, water content, crystal shape, board-life, spreadability, and flowability; bond strength; comprehensive strength; setting time; sand-carrying capacity; hydraulicity; free lime content; vapor permeability; flexibility; and resistance to sulfates.

These qualities are affected by many factors during each step of manufacturing and installation, including the original ingredients of the source of lime; added ingredients before and during firing including inclusion of compounds from the fuel exhaust; firing temperature and duration; method of slaking including a hot mix (quicklime added to sand and water to make mortar), dry slaking and wet slaking; ratio of the mixture with aggregates and water; the sizes and types of aggregate; contaminants in the mixing water; workmanship; and rate of drying during curing.

The special attributes of Type S are its "...ability to develop high, early plasticity and higher water retentivity and by a limitation on its unhydrated oxide content.

Type S lime is not considered reliable as a pure binder in mortar due to high burning temperatures during production.

The Romans made concrete by mixing lime and volcanic ash to create a pozzolanic reaction.