Gravel is loose, natural rock material made up of rounded grains of roughly 4 to 63 mm. It is used as the coarse aggregate in concrete, as a free-draining material, and as a decorative surfacing for paths and drives.
Characteristics
- Rounded grains — worn smooth by water action, unlike angular crushed stone
- Grain size — typically 4 to 63 mm, between sand and cobbles
- Free-draining — the loose, rounded grains let water pass easily
- Natural material — sourced from rivers, pits and glacial deposits
Application
Uses of gravel
- Coarse aggregate — the bulk of the stone content in concrete
- Drainage — as a permeable fill around land drains and behind retaining walls
- Surfacing — decorative gravel for paths, drives and gardens
- Bedding — a granular bed for pipes and paving
Selecting gravel
- The grain size is matched to the use, for example smaller grades for surfacing and larger for drainage
- For concrete, clean, well-graded gravel gives a strong, workable mix
Related Terms
- Aggregate
- Concrete
- Gravel and chippings
- Sand
- Drainage
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