Formation of aluminosilicate geopolymers from 1:1 layer-lattice minerals pre-treated by various methods: a comparative study
- 437 Downloads
Materials resembling aluminosilicate geopolymers have been prepared from the kaolinitic 1:1 layer lattice aluminosilicate clay mineral halloysite by reaction with sodium silicate solution under alkaline conditions. The effect on geopolymer formation of pretreating the clay mineral reactant by heating, high-energy grinding or exposure to acid or alkali was monitored by the ability of the samples to cure and harden, and by XRD, 27Al and 29Si solid-state MAS NMR spectroscopy. Only samples prepared from the fully thermally dehydroxylated clay showed the typical XRD and NMR geopolymer characteristics. Less complete reaction was found in samples pretreated by highly energetic grinding, whereas samples exposed to chemical pretreatment with dilute acid did not react to form viable geopolymers. Pretreatment with dilute alkali produced a zeolite which reacted with sodium silicate, but the hardened sample was not X-ray amorphous and showed subtle differences in its NMR spectra. These results are discussed in terms of the vital role played in the early stages of the reaction sequence by the presence of labile aluminium. The efficacy of the various pretreatment methods is related to their ability to render the aluminium source (the solid aluminosilicate clay) sufficiently soluble in alkali.
KeywordsGeopolymer Sodium Silicate Solution Thermal Pretreatment Sodium Aluminium Silicate ICDD File
- 3.Berg LG, Demidenko BA, Remiznikova VA, Nizamov MS (1970) Stroit Mater 10:22Google Scholar
- 4.MacKenzie KJD, Smith ME (2002) Multinuclear solid state NMR of inorganic materials, Pergamon Materials Series, vol 6. Pergamon/Elsevier, OxfordGoogle Scholar
- 5.MacKenzie KJD (2003) Adv. In Ceram. Matrix Composites IX, Ceram. Trans. 153:175Google Scholar
- 10.Brew DRM, MacKenzie KJD (2005) Fresh insights into geopolymer formulations: the roles of sodium silicate and sodium aluminate. Proc. World Geopolymer Conf., St. Quentin, France, p 27Google Scholar