Pozzolanic Techniques

Pozzolanic techniques involve mixing a siliceous (pozzolanic) material with other alkaline earths such as lime or gypsum in the presence of water to produce a concrete-like mass. This technique generally involves pozzolanic reactions between Si02, A1203, Fe203, and available calcium in lime. The results of these reactions are very stable and strong calcium silicates and aluminates that can be considered the equivalent of portland cement in initiating the cementation process. The most common pozzolanic materials used in stabilization/solidification of wastes are fly ash, ground blast-furnace slag, and cement kiln dust. The use of these materials, themselves considered by-products of little commercial value, to stabilize/solidify another waste may offer economic advantages. The vulnerability of the final product to acidic leaching is the major disadvantage of this technique. Combined cement-pozzolanic processes can be used to give a better and more economical final waste containment.

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