A comparative study on the mechanical and acid resistance characteristics of ambient temperature-cured glass waste and fly ash-based geopolymeric masonry mortars

This article reports a comparative analysis between glass waste and fly ash (which is the most studied waste for the alkali-activated products) to measure their effectiveness as a sole precursor to produce geopolymers. Globally, around 11.4 million tonnes of glass waste is generated per annum, and this needs to be managed properly. To address this issue, in this study, glass waste which was mostly manufactured bottles and containers was used in pulverized form. The molarity of the sodium hydroxide (NaOH) solution was kept as 6 M, 8 M, and 10 M. The sodium silicate-to-sodium hydroxide (Na2SiO3/NaOH) solution mix ratio was varied between 1.5 and 3.5. Mechanical (compressive and flexural strength) and durability (resistance to different levels of sulfuric acid) aspects were studied along with micro-analysis (structural, elemental, and thermal). Controlled ambient temperature curing was followed for all the samples. Our findings showed that mechanical properties were dependent on the molarity, silicate modulus, and alkaline mixture (AM) ratio. The glass waste showed substantial amount of long-term strength development over fly ash with a maximum compressive strength gain at 28 d and 90 d curing age of 90% and 194% for 8M1.5AM and 6M1.5AM mixture, respectively. For flexural strength, it was 49% and 62% gain at 28-d and 90-d curing, respectively, for 10M1.5AM mixture. The glass waste also offered relatively higher resistance to acid attack with a maximum compressive strength loss of 61% and 55.7%, whereas fly ash-based mixtures recorded 75% and 71.73% reduction for 5% and 3% H2SO4 attack for 28 d, respectively. Field emission scanning electron microscopy (FE-SEM) revealed that the glass waste specimens were more compact than fly ash-based specimens. Thermogravimetric analysis (TGA) results indicate that glass waste-based geopolymers are more thermally resistant than fly ash-based geopolymers when exposed to a systematic increment in temperature. Ultimately, promising results in terms of mechanical and durability aspects propose the use of glass waste as a binder in geopolymeric masonry mortar applications. Glass waste has a full potential to be a sole precursor to produce geopolymer under ambient temperature curing conditions. This will contribute towards sustainable environment by paving path for an effective utilization of the glass waste.