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Decomposed Granite Ballast

Decomposed granite aggregate is often chosen as the decomposed granite ballast used to support the rails in railway construction. As with roadbuilding, granite aggregate is popular with track layers due to its strength, durability, and excellent drainage-promoting qualities.

Granite is the most common igneous rock (rocks formed through the cooling and solidification of magma or lava) on Earth. In the case of granite, it originally crystallizes below Earth’s surface, where its slow cooling allows large crystals to form. You may have seen granite take shape as some of America’s favorite sights like Yosemite Valley or a few guys on Mount Rushmore. Granite has also been mined and used for daily applications for thousands of years, from ancient hand tools to modern-day countertops.

Decomposed granite is the completely natural derivative of granite. When granite erodes and endures weathering over time, it easily starts flaking and crumbling away from its parent source. This decomposed granite crumbles into various sizes of particles and can be further crushed and screened to specific sizes for different project needs. Granite weathers into decomposed granite in part because one of its components, feldspar, chemically weathers into a clay mineral called kaolin, which, when exposed to more water, further deteriorates.

TYPES OF DECOMPOSED GRANITE

Although there are at least 30 colors and varying degrees of particle sizes, decomposed granite basically comes in three forms: natural, stabilized, and resin-coated.

  • Natural DG is used as a mulch material and can be spread around trees and garden beds much like wood mulch. It will continue to weather after it is put in place and provides nutrients to surrounding soil and plants. It lasts longer than most other mulch materials and will not attract pests.
  • For a path or patio, DG with stabilizers (which serve as a binder) is the best solution. Stabilized DG is often added on top of another gravel material, tamped down, then left with a thin loose layer on top.
  • DG with resin for driveways has a similar surface to asphalt, but has a more natural look and is permeable.

PRODUCT USES AND APPLICATION

Decomposed granite as a crushed stone form is used as a pavement building material. It is used on driveways, garden walkways, bocce courts and petanque terrain and urban, regional, and national park walkways and heavy-use paths. DG can be installed and compacted to meet handicapped accessibility specifications and criteria. Different colors are available based on the various natural ranges available from different quarry sources, and polymeric stabilizers and other additives can be included to change the properties of the natural material. Decomposed granite is also sometimes used as a component of soil mixtures for cultivating bonsai.

While DG is most commonly used for paths, driveways, garden trails, and as a xeriscape ground cover, it can also be used to create smooth visual transitions between formal garden and wilderness. One of its advantages is that it breaks down, so any DG that migrates into a lawn or planting beds does not cause problems the way gravel does. Lining a path or patio with a black metal strip (which will disappear if buried low enough) will help keep it in place.

 

SOURCES

A Short Guide to What You Need to Know about Decomposed Granite. KAFKA GRANITE. https://www.kafkagranite.com/short-guide-need-know-decomposed-granite
Hardscaping 101: Decomposed Granite. GARDENISTA https://www.gardenista.com/posts/hardscaping-101-decomposed-granite/

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