In situ inorganic foams prepared from various clays at low temperature

Geopolymers are amorphous three-dimensional aluminosilicate binder materials that may be synthesized at room or slightly higher temperature by alkaline activation of aluminosilicates obtained from industrial wastes, calcined clays, natural minerals or mixtures of two or more of these materials. Among the different families of geopolymers, those based on potassium show modified thermal and mechanical properties due to the larger size of the potassium ion compared to sodium. This work deals with the preparation of geopolymer foams based on potassium silicate, industrial waste and various types of clays (kaolin, metakaolin, illite or montmorillonite). The influence of the clays used is assessed in terms of clay reactivity using structural data determined by FTIR spectroscopy, thermal analysis, XRD, and SEM characterizations. In situ geopolymer foam was obtained from all of the clays but its characteristics depended on the nature of the clays, including their structural alteration and chemistry. The extent of destruction of the clay structure was partial for kaolinite but was greater for illite, followed by montmorillonite. These inorganic foams have a potential use in housing construction, since they display thermal insulating properties.