Abstract
Waste glass is a type of construction and demolition waste (CDW), which carries significant environmental burdens and can be recycled. In this study, a foamed alkali-activated glass (FAAG) via the use of milled waste glass was synthesized in low-temperature (i.e., 80 ⁰C). The influence of foaming agent (i.e., aluminum powder) content on the foaming process of samples was investigated and optimized in view of their performance. The optimum mix formulation, which is FAAG with 10% aluminum powder was then selected, and followed by the measurement of the water-resistance and absorption, impact resistance and thermal conductivity of the prepared FAAG. X-ray diffraction was also involved to identify the phase formation within the samples. Finally, the environmental impacts related to the preparation of 1 kg FAAG were obtained. Results shows that a type of more sustainable FAAG compared with the commercial product was successfully developed in low-temperature, revealing the low thermal conductivity of ~0.13 W/(m∙K) with a density of ~0.59 g/cm3 and compressive strength of ~5.52 MPa, which is 97% higher than the commercial product. Meanwhile, in addition to a foaming agent, aluminum powder is also acting as a key component in the geopolymerization of samples, facilitating the formation of aluminosilicate that provides strength.
Highlights
In the European Union, construction and demolition waste (CDW) is becoming a serious issue, accounting for around 25–30% of all waste generated
Following the work from Kastiukas et al (2020), indicated that in the United Kingdom, due to the shutdown of the electricity plants and the upgrade of equipment in the steel industry, there will be a shortage of fly ash and ground-granulated blast-furnace slag soon, which are widely used as precursors in the preparation of geopolymers previously
In addition to a foaming agent, aluminum powder is working as a key component in the geopolymerization of waste glass, and the produced re-silicate within the samples led to the strength development of samples, indicating that milled waste glass with aluminum powder can be used to synthesize foamed product for thermal insulation
Summary
In the European Union, construction and demolition waste (CDW) is becoming a serious issue, accounting for around 25–30% of all waste generated. The use of waste glass treatment in the construction sector is investigated It can be used in the preparation of alkali-activated binders or geopolymers. The raw materials used to produce the FAAG in this study consisted of waste glass (received from the local municipality of Covilhã, Portugal), sodium hydroxide (NaOH, 98%) (Fisher Scientific, Germany), sodium silicate (Na2SiO3) (Solvay SA, Portugal), and aluminum powder (Sigma Aldrich, United Kingdom). The raw material (i.e., waste glass) and the crushed FAAG samples after compression test with different amounts of the foaming agent were ground and sieved, and the powder was stored in ethanol for 3 days to stop hydration and dried prior to testing. The Cumulative Energy Demand method incorporates the sum of direct and indirect energy consumption (mega joule) throughout the entire life cycle, including the energy consumed during the production of raw materials and transportation (Bribián et al, 2011)
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