Recycling of glass waste and spent alkaline batteries cathodes into insulation materials

Expanded glass with thermal and acoustic insulation properties are obtained from a foaming blend composed of 97% glass waste and 3% expanding agent. This latter is a blend of carbon and manganese oxides, recovered from exhausted alkaline batteries. The samples are produced after heating the mixture in a ventilated furnace at temperatures between 850 and 950 °C, for times between 15 and 60 min. Mechanical, thermal and acoustic properties are characterized as a function of process parameters. The glass foam samples have densities in the range of 290–350 kg/m3, porosity of 86–90%, thermal conductivity values of 107–120 mW m−1 K−1, noise reducing factors of 0.2–0.3 and compressive strengths up to 4.6 MPa. Although the resulting insulating performances are not as outstanding as those of polymer foams or mineral wool, these materials can emerge as competitive candidates for applications requiring low weight and moderate thermal and acoustic insulation properties, in combination with non-flammability and high temperature load bearing-capacity. Moreover, the use of 100% recycled raw materials limits the energy and the resource required for their production, if compared to those needed for the extraction, transportation, and processing of primary raw materials, making these foams attractive also in terms of environmental impact.