Valorization of phosphogypsum derived from Algerian phosphate ores for applications in construction materials

The sedimentary deposits of the wilaya of Tebessa contain the largest phosphate reserves in Algeria, estimated at 2 billion tons by the Phosphate Mining Company (SOMIPHOS). Phosphate ores constitute a fundamental raw material for multiple uses, particularly in the production of fertilizers, phosphate-based food supplements, phosphoric acid, and more. The development of the phosphate industry, along with fertilizer and phosphoric acid production, has led to the accumulation of large quantities of industrial waste such as phosphogypsum Fig1.

This material may contain various problematic impurities, including phosphates (P₂O₅), fluorides (F⁻), heavy metals (Cd, Cr, Pb), naturally occurring trace elements, as well as residual organic matter. All these constituents can have harmful effects on public health and the environment. Currently, the environmental challenges associated with the massive production and accumulation of phosphogypsum are raising increasing concerns. In this context, integrating phosphogypsum into the cement manufacturing process appears to be a promising solution. This approach not only enables the valorization of a potentially polluting industrial by-product but also helps reduce its environmental impact by providing a partial yet significant recycling pathway.

To ensure safe storage of phosphogypsum as well as its appropriate use, this research project proposes solutions and methods for its treatment, targeting the removal or reduction of polluting elements, and exploring its potential applications in construction materials. Reducing the toxic elements in phosphogypsum is a key step for its safe valorization, particularly in construction applications.

In the context of applications in mortars and concrete, the use of phosphogypsum as a partial substitute for sand and/or cement raises major scientific and technical challenges. These include the effectiveness and stability of decontamination treatments, the impact of residual impurities on cement hydration mechanisms, the physicochemical and mechanical compatibility of phosphogypsum with concrete constituents, as well as the determination of optimal substitution rates. The durability of the resulting composite materials, along with regulatory and standard requirements, also represents significant barriers to overcome.

This project aims to provide concrete answers to these challenges by developing suitable and efficient treatment protocols for phosphogypsum from Tebessa. It will also involve scientifically evaluating its suitability for use as a partial substitute for sand and/or cement in mortar and concrete formulations. The ultimate objective is to propose valorization solutions that are technically robust, economically viable, and environmentally sustainable, thereby contributing to more responsible management of industrial waste and promoting a more sustainable construction materials sector in Algeria.