From by-product to sustainable building material: Reusing phosphate washing sludge for eco-friendly red brick production

Abstract

Brick production is a major contributor to the construction industry, but the process requires a significant amount of non-renewable clay. To address this, researchers have explored incorporating waste materials into clay bricks. This study investigates phosphate-washing sludge (PS-K) as an additive in clay bricks and evaluates its impact on physical, mechanical, and thermal properties. Laboratory and pilot-scale experiments were conducted to determine the optimal quantity of PS-K for waste reduction. Five compositions with PS-K percentages ranging from 0% to 50% were prepared in the laboratory based on the raw materials' chemical composition. The bricks were shaped using a humic method, underwent drying and cooking processes, and underwent physical analysis, including bulk density, apparent porosity, and water absorption tests. Microstructural analysis was performed using a scanning electron microscope, while thermal conductivity and compressive strength were evaluated.Results showed that increasing PS-K content led to higher open porosity and water absorption in the bricks. At 50% waste content, the open porosity reached 52%, and water absorption reached 32%. The relationship between waste content and porosity/water absorption was nonlinear, with greater increases observed at higher waste contents. Incorporating up to 30% sludge met standard brick requirements.Pilot-scale experiments using the optimal 30% PS-K content demonstrated similar porosity and water absorption trends as observed in the laboratory samples. The bricks' extrusion shaping process and final appearance after drying were successfully demonstrated.This research provides valuable insights into utilizing phosphate-washing sludge in clay bricks, offering a potential waste management solution and reducing clay consumption in brick production. The findings demonstrate the feasibility of incorporating PS-K into bricks while meeting industry standards, contributing to sustainable practices in the construction sector.