A novel eco-friendly foaming technique for developing sustainable glass foams from the waste glass

Abstract: The complex waste glass (WG) coming from the automotive vehicle industry has very low recycling potential and goes mainly to landfills. This research aims to develop a sustainable and eco-friendly method to prepare lightweight glass foams using this waste. Glass foams are porous, lightweight materials and are extensively used in various industry sectors. Gel-casting technique is known as an eco-friendly method for making glass foams by vigorous mechanical foaming. In gel-casting, the pore structure of the foam is initially stabilized by gelation of alkali-activated precursors and then strengthened by viscous flow sintering. However, the gelation process requires a prolonged activation and precuring processes of precursors at a raised temperature which is not energy-efficient. Therefore, this research aimed to reduce the gelation time and improve the pore characteristics in glass foams by a novel combined mechanical and chemical foaming technique. After quick alkali-activation of precursors and foaming, the hardened glass foams were sintered at 700–800°C temperatures. It is concluded that the lengthy gelation process can be replaced by quick activation and combined foaming technique to develop desirable pore characteristics. The low-speed mechanical foaming imposes low shearing stress on the activated paste, which reduces pore coalescing. Additionally, chemical foaming by low-concentration hydrogen peroxide reduces anisotropic pore formation. Consequently, the pore structure in glass foam improves. The proposed eco-friendly foaming method is useful for producing glass foams in large scale with desirable density (300–400 kg/m3), thermal conductivity (<0.10 W/(mK)) and compressive strength (∼2 MPa).

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