MULTISCALE IMPACT AND ENVIRONMENTAL SUSTAINABILITY OF PHOSPHOGYPSUM-BASED CONSTRUCTION MATERIALS

The industrial-scale production of phosphoric acid generates large quantities of phosphogypsum (PG), posing significant environmental challenges, particularly in Morocco. This study proposes a sustainable approach for the reuse of phosphogypsum in construction materials. Raw PG is purified by selective reverse flotation to remove silica, then thermally modified (600–800 °C) to obtain reactive and stable phases. A multiscale analysis shows that a high PG substitution rate reduces the Young’s modulus, while the Poisson’s ratio remains stable (0.19–0.20). PG also acts as a porosity regulator, improves the material’s thermal performance, and provides significant fire resistance (0.19 W/m·K). At the structural level, FRP/steel confinement increases the load-bearing capacity of PG-filled columns by more than 45%. From an environmental perspective, the incorporation of PG neutralizes the pH of the planting concrete (10.2 to 8.0) and promotes highly permeable pavements. The reuse of PG reduces the carbon footprint by approximately 50%, sequesters up to 215.76 g of CO₂/kg, and immobilizes heavy metals. This approach transforms industrial waste into a resource for sustainable construction.