Utilisation of solid waste polyurethane foam as coarse aggregate in concrete: an experimental study with ecological and cost assessment

Industries generate a lot of solid waste, including polyurethane foam waste from refrigeration, automobile, and construction industries. Most of this waste is incinerated or dumped in landfills, causing harm to the environment and loss of land usage. Natural coarse aggregates used in concrete are expensive and require excavation, which affects the environment. This study replaced coarse aggregate with polyurethane foam in concrete to reduce waste disposal and natural coarse aggregate extraction. The replacements were 0, 10, 20, 30, and 40% by volume of coarse aggregate. Experimental investigations were carried out to evaluate the polyurethane foam concrete fresh properties, hardened properties, water absorption, ultrasonic pulse velocity, and microstructure characterisation. Results showed that concrete compressive strengths exceeded 17 MPa and densities less than 2000 kg/m3 when 30 and 40% of coarse aggregate were replaced by polyurethane foam, which satisfied lightweight concrete criteria. The 10 and 20% coarse aggregate replacements showed compressive strengths greater than 20 MPa, with densities above 2000 kg/m3. In all replacements, the ultrasonic pulse velocity value was more than 3.5 km/s. Moreover, an ecological and economic study showed that PU foam concrete had lower embodied energy, embodied carbon emissions, and cost compared to conventional concrete.