Valorization of fine fraction from legacy waste as fired bricks: A step towards circular economy

Old landfills and dumpsites, created due to a linear approach towards municipal solid waste (MSW) management, are one of the major environmental hazards, especially in developing countries. Around 50% of the dumped waste can be characterized as fine fraction (FF), making its recovery a vital parameter for achieving a circular economy. This study investigates the application of FF obtained from the Indian MSW dumpsite to replace topsoil used for fired brick production, which is one of the primary construction materials in India. The raw materials (FF and clay) were mixed in different proportions and fired at a temperature of 800–1000 °C. Physicochemical, mechanical and environmental properties were analyzed for fired bricks using standard methods. Results showed that the fired bricks produced from FF had low density and thermal conductivity than control bricks providing advantages over conventional bricks for transportation and energy savings. The compressive strength (CS) of the bricks increased with an increase in temperature and reduced with an increase in FF, suggesting only a certain amount of clay can be replaced. Hence further optimization using response surface modelling was carried out. The optimization results showed that clay could be substituted up to 23% at 1000 °C (CS = 37.5 N/mm2) by FF to meet Indian regulatory limits for CS. Toxicity characteristic leaching procedure test showed that fired bricks produced from FF are safe for application. The study shows that FF can substitute part of clay in fired brick production, which can help to curb topsoil exploitation while achieving a circular economy by bringing dumped FF back to the anthropogenic material cycle.