The development of valuable new products (‘up-cycling’) is fundamental for avoiding any landfilling ofthe glass fractions (‘waste glasses’) which are normally unemployed, e.g. due to polymer and metalcontaminations [1]. The balance between inputs and outputs of supplementary materials, energy andemissions, however, remains challenging. This projects aims at defining new structural and functionalmaterials by alkali activation treatments at nearly room temperature, triggered by the samechemical composition of waste glasses, possibly mixed with other inorganic (and mainlyglassy) residues.Alkali activation corresponds to the extensive dissolution of silicate and alumino-silicatepowders, suspended in concentrated aqueous solutions of alkali hydroxides, silicates andaluminates. With a proper balance among constituent oxides (SiO2, Al2O3, alkali oxides),condensation reactions of the dissolution products determine, at nearly room temperature,stable gels, featuring a three-dimensional ‘zeolite-like’ network structure (resulting from thebridging of SiO4 and AlO4 units, the latter being stabilized by alkali ions in the surroundings).In this framework, waste glasses have been widely considered, as providers of SiO2 and alkalioxides, after dissolution in highly concentrated attacking solutions [2]. The present project,according to very recent findings [3], aims at developing far more sustainable alkali-activatedmaterials, operating with diluted alkali hydroxide solutions (molarity not exceeding 3M).Zeolite-gels may result from the surface activation of fine powders of relatively Al2O3-richwaste glasses or blends of waste glass with other Al2O3-rich residues, such as volcanicmaterials [4,5].A full circularity can be achieved only with a clear identification of useful target products [1].As a further proof of sustainability, the present project aims at defining both dense andporous structural components, to replace building products, such as clay bricks, lightweightconcrete, glass and ceramic foams, already obtained by energy- and material-demandingprocesses. Dense products will imply the adoption of glass cullet or other inorganic residuesalso in form of coarse powders, bound by thin layers of matrix resulting from fine powders. Inparallel, cellular products will rely on the gas incorporation in matrices at the early stages ofgelation, by intensive mechanical stirring and/or decomposition of foaming agents, possibly
supported by surfactants. The new products will undergo an extensive environmental impactanalysis, in form of leaching (to assess the effective permanent stabilization of pollutants,from cullet and/or other residues) and life cycle sustainability assessment. Finally, cellularmaterials, not only resulting from foaming, but also from the application of modern additivemanufacturing technologies, will be considered for their potential in water remediation, inanalogy with several alkali-activated systems