Development of Unfired Clay Bricks with Alumina Waste from Liquid Nitrogen Production: A Sustainable Alternative for Construction Materials

A major breakthrough in environmentally friendly building materials is the development of sustainable unfired clay bricks including alumina waste produced during liquid nitrogen generation. Though used extensively, conventional fired clay bricks require energy-intensive manufacturing techniques that produce significant amounts of CO2 and aggravate environmental damage. By removing the need for high-temperature firing and allowing for the valorization of industrial byproducts including alumina waste and lateritic soil, unfired clay bricks offer a reasonable low-carbon alternative. High silica and alumina contents define the alumina waste, which shows pozzolanic reactivity, thus improving the physicomechanical performance of the bricks. With alumina waste substituting 0–8.57% of the cement content, seven different formulations showed improvements in compressive strength, reduced water absorption, and optimal thermal conductivity. Especially, the mechanical performance was much enhanced with alumina waste inclusion up to 30%, without sacrificing thermal insulation capacity or moisture resistance. Further supporting the environmental and financial sustainability of the suggested brick compositions is the economic viability of using industrial waste and regionally derived soils. A comparative analysis of the conventional fired bricks shows that the unfired substitutes have a much lower environmental impact and show better mechanical properties, including greater compressive strength and modulus of rupture. These results support the more general goals of circular economy systems and low-carbon urban development by highlighting the feasibility of including alumina waste and lateritic soil into sustainable building materials. Using such waste-derived inputs in building fits world initiatives to lower resource consumption, lower greenhouse gas emissions, and build strong infrastructure systems.