Abstract
Food containers made from glass are separately collected from urban solid waste at 76% in most parts of Europe. The cullet glass finds its way to re-melting, while the debris is often disposed of. With this contribution, we suggest an upcycling process where glass debris is simply ground without any washing operation and added to an alkali-activated paste. Metakaolin-based geopolymer mortar added with coarsely ground glass waste as fine aggregate has been prepared via alkali activation with NaOH and Na-silicate. After 7, 14 and 28 days of room temperature curing time, the 3D geopolymer network was investigated by Fourier-transform infrared spectroscopy (FT-IR). Vibrational spectra revealed the geopolymerization occurrences, results which have been supported by both FT-IR deconvoluted spectra and thermogravimetric analysis (TGA). Finally, the antibacterial properties were investigated against both gram-negative (E. coli) and gram-positive (E. faecalis) bacterial strains. The results suggest the ability of the 28 days cured geopolymers to inhibit the growth of the gram-negative bacterium assayed.
Highlights
Within recent decades, geopolymers have become suitable replacements for conventional concrete materials, and many efforts have been carried out to improve their functional properties while, at the same time, trying to increase their environmental performance [1].The alkali activation of alkali aluminosilicate glass yielded cements with high compressive strength (65 MPa after 20 h at 85 ◦ C) [2], and the alkali activation of vitreous calcium aluminosilicate derived from glass fiber waste generated mortar samples with even higher compressive strengths [3]
Abdollahnejad et al [11] compared the mechanical properties of waste glass-based geopolymers with and without the addition of lime, revealing that after 28 days of curing time, the formulation obtained with both additives possessed increased compressive strength (10 MPa) with respect to the one without the lime (0.5 MPa)
We noticed that the GP and GP/waste glass (WG) 20% were completely hardened with respect to the GP/WG 50, and that 60% showed an aliquot of unreacted alkaline solution on the upper surface
Summary
Geopolymers have become suitable replacements for conventional concrete materials, and many efforts have been carried out to improve their functional properties while, at the same time, trying to increase their environmental performance [1].The alkali activation of alkali aluminosilicate glass yielded cements with high compressive strength (65 MPa after 20 h at 85 ◦ C) [2], and the alkali activation of vitreous calcium aluminosilicate derived from glass fiber waste generated mortar samples with even higher compressive strengths (up to 77 MPa after 3 days at 65 ◦ C) [3]. In order to increase energy saving, the curing of the alkali activated formulations can occur at room temperature [7] In this particular condition, the binding efficiency of container glass is limited, making the addition of other binders, such as metakaolin, essential. Abdollahnejad et al [11] compared the mechanical properties of waste glass-based geopolymers with and without the addition of lime, revealing that after 28 days of curing time, the formulation obtained with both additives possessed increased compressive strength (10 MPa) with respect to the one without the lime (0.5 MPa). Jiang et al 2020 [12] reported the influence of heat treatment (from 20 to 1200 ◦ C) on the compressive strength of waste glass added to fly ash-based geopolymers. After treating at 20 ◦ C, the geopolymer made up of 20 wt % of waste glass and 80 wt % of fly ash has a compressive strength of ca. 54 MPa, but a heat treatment up to 1200 ◦ C highly decreases the compressive strength (less than 5 MPa)
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