Decomposed granite is sometimes used in road construction, although it must be compacted to form a firm driving surface.
Decomposed granite, sometimes referred to as DG, is most commonly recognized as a building and landscape material. It is popular in trail, parking and road construction, as well as backyard landscaping. Decomposed granite consists of weathered granitic particles that range in size from gravel to silt and often include some clay. The name decomposed granite refers to the fact that the particles are the result of natural weathering, or decomposition, of the granite rock.
One of the most common places to find DG is on hiking trails. The material is reasonably stable when compressed and yet remains a permeable material, allowing for satisfactory drainage. In addition to footpaths, decomposed granite is commonly used to build driveways and parking areas. Decomposed granite is also sometimes used in road construction, although it must be compacted to form a firm driving surface.
Decomposed granite is popular in landscaping as a hardscape material. It can be used as a ground cover, mulch, patio base or for creating paths. Decomposed granite is a very eco-friendly choice because it is a natural product, is permeable and provides a rigid landscape that does not require water. Once the granite is in place, it will continue to weather, which adds beneficial nutrients to the soil and surrounding plants. Not surprisingly, decomposed granite is a particularly popular landscape choice in arid regions.
Depending on the climate and intended use, the DG can be worn alone with moderate compression to hold it in place, or it can be put in place with stabilizers. If the granite is being spread out on its own, it is usually contained with some sort of border or frame to keep the granite from washing out easily. In contrast, if the decomposed granite is being fixed with stabilizers or resins, the hardscape with will be more permanent and stable, but permeability will be reduced, making drainage an important consideration.
Decomposed granite generally refers only to naturally weathered granite; however, it is often discussed interchangeably with crushed gravel and crushed stone. Each of these products has angled parts and usually a percentage of thin parts. They are often used for similar types of building or landscaping processes.
The formation of decomposed granite occurs over time and is the natural result of weathering and erosion of granitic rocks. Wind and water physically and chemically affect the granite, eventually breaking up the small pieces that make up the decomposed granite. The final product is mined in granite quarries, often alongside other granite products such as large blocks, slabs and manufactured crushed granite.