Difference Between Pool Base & Horticultural Vermiculite

Vermiculite

• Vermiculite is the heat-expanded form of magnesium-aluminum-iron silicate, a mineral that is often found in volcanic deposits. In its raw form, it displays shiny flakes resembling mica in appearance and in chemical composition. Its name has origins in the Latin vermiculare, which means “to breed worms,” because of its exfoliated appearance after heat expansion. The suffix “-ite” designates it as a mineral. Vermiculite deposits exist in many countries, with the top-producing mines in the United States found in South Carolina, according to the Mining Association of South Carolina.

Pool Base

• Vermiculite is one component of pool base mixtures that are used to line swimming pools. Mixed with Portland cement and other binding additives, vermiculite is applied to the bottom of a pool and partially up the sides. This protective layer helps insulate in-ground pool bottoms from cold ground temperatures, according to The Vermiculite Association. Pool heaters do not have to work as hard, which makes vermiculite liners cost-effective in the long run. In above-ground pools, vermiculite provides soft padding underneath the vinyl liner.

Horticulture

• Vermiculite also has numerous horticultural uses. When added to potting mixes, vermiculite is a sterile, lightweight additive that retains moisture and increases aeration, particularly in containers. In the landscape, gardeners use vermiculite to lessen compaction in heavy soils, such as clay, or to increase water retention in poor soils. Used alone or mixed with peat moss, vermiculite makes a seed-starting mix. Horticulturists use vermiculite mixed with pine bark as a medium to propagate plants from stem cuttings.

Differences

• Vermiculite has the same chemical composition and qualities whether it’s used for pool bases and liners or for horticultural applications. It is the size, or grade, of vermiculite that makes the difference in which product is chosen. For most horticultural uses, especially propagating mixes for stem cuttings, potting mixes for container plants and amending soil, coarse grades of vermiculite are used. The same fine grade of vermiculite is used for seed-starting mixes and for pool bases. When packaged for swimming-pool use, vermiculite is sometimes called builder aggregate, or concrete aggregate, although it is the same product with the same particle size as fine-grade horticultural vermiculite.