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Gravel is composed of unconsolidated rock fragments that have a general particle size range and include size classes from granule- to boulder-sized fragments. Gravel can be sub-categorized into granule (>2 to 4mm) and boulder (>64 to 256mm). One cubic yard of gravel typically weighs about 3000 pounds (or a cubic meter is about 1,800 kilograms).
Gravel is an important commercial product, with a number of applications. Many roadways are surfaced with gravel, especially in rural areas.
Aquaponics and HydroponicsEdit
Gravel can be used as a Substratum. Compared to Expanded Clay and many other materiels, Gravel is rather heavy. Gravel-filled growbeds must have stable foundations. In most areas of the world, Gravel is the cheapest choice.
Gravel containing limestone affects the pH and should be avoided. A simple test for limestone is to mix a sample of gravel with regular vinegar. If you see bubbles rising in the suspension, the sample contains limestone.