Aqueous leaching of an industrial geopolymer
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The temperature and pH dependence of the water leaching of a geopolymer crypt material has been studied using mainly 75-150 m powders exposed to large aqueous volumes. Over the pH 3-12 range, little variation in elemental extraction was seen, although even in dilute solutions, significant pH excursions were observed. Derived leach rates and behaviour at different pHs were broadly similar to those observed by others for metakaolin geopolymers and borosilicate glasses; thus the most leachable species was Na, leach rates decreased sharply with time, and Si leaching was significant in alkaline solutions. Even after 1 year in water at 90C, only a few tens of microns of the geopolymer binder phase were leached and no crystalline alteration products were observed.