Limestone is a sedimentary rock made up largely of calcium carbonate (CaCO₃), usually in the form of the mineral calcite. The rock forms on the beds of seas and lakes through the accumulation of the calcareous skeletons and shells of organisms, and sometimes through the chemical precipitation of lime from water.
Properties
- Relatively soft — limestone is easier to work than, say, granite, but this also makes it more susceptible to wear and weathering
- Porous — many types of limestone absorb water, making them vulnerable to frost and acid rain
- Calcareous — it reacts with acids, which means it can slowly dissolve
Application
Limestone is used in construction in several ways:
- Natural stone — as facade cladding, floor tiles, sills, and decorative work. Well-known types include French limestone and Belgian bluestone (a dense limestone)
- Raw material for lime — burning limestone produces quicklime, the basis for lime mortar and plaster
- Raw material for cement — limestone is the main raw material in the production of Portland cement
- Aggregate — crushed limestone serves as aggregate in concrete and as a base layer under roads
Points to note
Because limestone is porous and acid-sensitive, protection matters when it is used outdoors. In urban environments with air pollution, the surface can be attacked over time. Harder, dense types such as bluestone are more durable than soft, porous varieties.
Related terms
- Natural stone
- Bluestone
- Lime
- Cement
- Sedimentary rock
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