Enhancing the Upcycling of Soda-Lime Glass Waste in Alkali Activated Materials
TAMENI G. 1, CAMMELLI F. 1,2, ELSAYED H. 1,3, MAZZI A. 1, GAZZO S. 4, CONTRAFATTO L. 4, BERNARDO E. 1,2
1 Department of Industrial Engineering, University of Padova, Padova, Italy; 2 RU INSTM, University of Padova, Padova, Italy; 3 Refractories, Ceramics and Building Materials Department, National Research Centre, Cairo, Egypt; 4 Department of Civil Engineering and Architecture, University of Catania, Catania, Italy
With the purpose of decreasing both energy and raw materials consumption, alternative strategies for reducing environmental impact are proposed. Soda-lime glass is not completely recyclable nowadays; finer fractions of glass cullet remain practically unemployed, and they are mostly landfilled[[i]]. The present investigation aims at showing up-cycling strategies, concerning soda-lime glass, in order to obtain construction materials under weak alkaline activation (< 3M, NaOH). Simultaneously, volcanic ash from Mt. Etna, that currently represents a scrap, can be used alone or as a filler, as feedstock for alkali activated materials according to the large amount of silica and alumin [[ii]]. Fine glass and volcanic ash powder (< 75 μm) with different ash/glass proportion, are suspended in alkali solution, for a liquid/solid ratio of 0.42. Slurries, obtained by mixing for 30 min at 450 rpm, are cured for 3 days at 75°C, realizing a ‘cold consolidation’. Gel with variable amounts of volcanic ash are all stable, as proven by water boiling test; the gel from pure soda-lime glass, without ash, is just more sensitive to solid/liquid ratio and curing temperature. Synergy between soda-lime glass and volcanic ash is highlighted by high values of compressive strength; dense specimens, thanks to a suitable strength-to-density ratio, can be used in building materials production. Otherwise activated solutions can be used to manufacture inorganic highly porous foams, for thermal and acoustic insulation. Foams are obtained not by melting process, but by simple decomposition, during curing, of sodium perborate monohydrate (SPB) additive, with sodium dodecyl sulphate (SDS) as stabilizing agent.
[[i]] A. Ricon, G. Giacomello, M. Pasetto, E. Bernardo, Novel ‘inorganic gel casting’ prcess for the manufacturing of glass foams, J. Eur. Ceram. Soc. 37 (2017) 2227-2234 https://doi.org/10.1016/j.jclepro.2014.10.091
[[ii]] E. Bernardo, H. Elsayed, A. Mazzi, G.Tameni, S. Gazzo, L. Contrafatto, Double.life sustainable construction materials fromalkali activation of volcanic ash/ discarded glass mixture, Const. Build. Mat. 359 (2022) 129540, 10.1016/j.conbuildmat.2022.129540