Nearly room-temperature fabrication of waste glass-derived foams for sustainable insulation

A substantial proportion of glass waste is disposed of in landfills due to the limitations of conventional recycling methods in processing articles with specific chemical compositions or contamination, such as serigraphed glass, borosilicate glass, and glass mud residues. This study proposes an approach for managing such waste through the fabrication of highly porous, chemically stable glass foams at nearly room temperature, without the use of precious additives. Fine glass powders were homogeneously dispersed in weak alkaline suspensions, which were subsequently foamed by a combination of a limited amount of surfactant, foaming agent, and intensive mechanical stirring. The cellular structures were first stabilized through gelation and subsequently dried at 40 °C for 7 days. As an alternative, viscous flow sintering at 700 °C for 60 min was investigated as an end-of-life option for the first-generation green foams, resulting in porous glass-ceramic foams exhibiting an excellent strength-to-density ratio. The newly synthesized foams demonstrated an excellent compressive strength, ranging from 2 to 7 MPa, and a thermal conductivity of 0.13 W/m·°C, despite their high overall porosity of 68–73 %, which compares favourably to existing cement-based materials in terms of strength-to-density ratio and effective thermal conductivity.