| Economics |
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| Constructional uses & fill Aggregates are used in construction to provide drainage, fill voids, protect pipes, and to provide hard surfaces. They are also used in water filtration and sewage treatment processes. Water will percolate through a trench filled with aggregate more quickly than it will through the surrounding soil, thus enabling an area to be drained of surface water. This is frequently used alongside roads in order to disperse water collected from the asphalt surfacing.
Aggregate is an essential component of any building project. |
 Voids created around the foundations of buildings during construction are filled with aggregate because it is easier to compact than the original soil that was removed, resulting in a more solid finish that will support the structure. Aggregates generally are not affected by the weather as much as soils, particularly clay soils, and will not suffer from shrinkage cracking during dry spells. Pipes laid to convey treated water, or as conduits for cables, need to be protected from sharp objects in the ground and are therefore laid on, and surrounded by fine aggregate before trenches are backfilled. Unpaved roads and parking areas are covered in a surface layer of aggregate to provide a more solid surface for vehicles, from cycles to lorries. This prevents the vehicles from sinking into the soil, particularly during wet weather. Groundwater is filtered naturally through aquifers, often layers of sand and gravel, and only needs to be disinfected with chlorine before it is safe to use. This natural process can be replicated in treatment works to remove suspended solids from surface or stored water, before disinfection. In addition sand beds are used during the last stages of sewage treatment works as a final filter and cleaning process before the water is released into watercourses. In some cases reed beds are used at this stage, where the reeds will be grown on gravel. |
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