The aluminasilica sources ( fly ash , metakaolin and etc) are mixed with an activating solution(sodium hydroxide or potassium hydroxide ) that provides the alkalinity needed to liberate the Si and Al and possibly with an additional source of silica (sodium silicate is most commonly used).
Geopolymer is a product of inorganic polymerization. Geo-polymerization process was first proposed by Davidovits in 1978. He proposed that an alkaline liquid could be used to react with the silicon (Si) and the aluminium (Al) in a source material of geological origin or in byproduct materials such as fly ash and rice husk ash to produce binders. The chemical composition of the geopolymer is similar to natural zeolitic materials, but the micro-structure is amorphous instead of crystalline. The polymerization process involves a substantially fast chemical reaction under alkaline condition on Si-Al minerals, that results in a three dimensional polymeric chain and ring structure consisting of Si-O-Al-O bonds. A geopolymer can take one of the three basic forms as suggested by Davidovits:
• Poly (sialate), which has [-Si-O-Al-O-] as the repeating unit.
• Poly (sialate-siloxo), which has [-Si-O-Al-O-Si-O-] as the repeating unit.
• Poly (sialate-disiloxo), which has [-Si-O-Al-O-Si-O-Si-O-] as the repeating
unit.
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