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Materials (Basel). 2019 Feb 15;12(4). pii: E588. doi: 10.3390/ma12040588.

Glass-Ceramic Foams from 'Weak Alkali Activation' and Gel-Casting of Waste Glass/Fly Ash Mixtures.

Author information

1
Department of Industrial Engineering, University of Padova, Via Marzolo 9, Padova 35131, Italy. acacio.rinconromero@unipd.it.
2
Institute of Biomaterials, Department of Materials Science and Engineering, University of Erlangen-Nuremberg, Cauerstraße 6, 91058 Erlangen, Germany. nicoletta.t.toniolo@fau.de.
3
Institute of Biomaterials, Department of Materials Science and Engineering, University of Erlangen-Nuremberg, Cauerstraße 6, 91058 Erlangen, Germany. aldo.boccaccini@ww.uni-erlangen.de.
4
Department of Industrial Engineering, University of Padova, Via Marzolo 9, Padova 35131, Italy. enrico.bernardo@unipd.it.

Abstract

A 'weak alkali activation' was applied to aqueous suspensions based on soda lime glass and coal fly ash. Unlike in actual geopolymers, an extensive formation of zeolite-like gels was not expected, due to the low molarity of the alkali activator (NaOH) used. In any case, the suspension underwent gelation and presented a marked pseudoplastic behavior. A significant foaming could be achieved by air incorporation, in turn resulting from intensive mechanical stirring (with the help of a surfactant), before complete hardening. Dried foams were later subjected to heat treatment at 700⁻900 °C. The interactions between glass and fly ash, upon firing, determined the formation of new crystal phases, particularly nepheline (sodium alumino⁻silicate), with remarkable crushing strength (~6 MPa, with a porosity of about 70%). The fired materials, finally, demonstrated a successful stabilization of pollutants from fly ash and a low thermal conductivity that could be exploited for building applications.

KEYWORDS:

alkali activation; fly ash; glass–ceramic foams; inorganic gel casting; waste glass

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