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<p>Phosphate fertilizer industries produce a large quantity of phosphogypsum (PG) annually, which permanent storage raises technical and environmental constraints. However, this co-product valorization in civil engineering, particularly in road construction, is a promising solution within a circular economy. To evaluate this option, our experimental study focused on mixtures’ mechanical responses modelling by the Design of Experiment (DOE) method, consisting of PG from the Jorf Lasfar industrial complex treated with a hydraulic binder (cement C/road hydraulic binder HRB) and a granular corrector (sand S/ phosphate tailings T), meeting mechanical criteria of a subgrade/subbase pavement layer material. To do so, the Proctor test was used to find the optimum water content and dry density, and it was optimized using the same DOE method. In addition, environmental assessment, based on leaching tests measured on two mixtures suitable for each use, showed that all measured heavy metals (Cr, Cd, Pb, Cu, As, Zn, Ni) concentrations were far below international standard limits, due to either encapsulation in the crystalline structure of gypsum or thanks to cement treatment, which enabled trace metals to be fixed through the C–S–H formation. In addition, the mechanical strengths of the mixtures were improved, as shown by SEM and XRD investigations. Finally, a life-cycle analysis, based on industrial software, showed that a pavement structure with a sub-base and subgrade course composed of PG mixes reduces energy and water consumption by 50%, and CO<sub>2</sub> emissions by 30%.</p>

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Environmental Assessment of Phosphogypsum as Alternative Pavement Material

  • 期刊论文

  • 发表日期：

    2025年4月19日

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  • Chaimaa Diouri,
  • Moussaab Masskouri,
  • Sarra Meskini,
  • Khaled Lahlou,
  • Amina Alaoui,
  • Kamal El Omari

摘要

Phosphate fertilizer industries produce a large quantity of phosphogypsum (PG) annually, which permanent storage raises technical and environmental constraints. However, this co-product valorization in civil engineering, particularly in road construction, is a promising solution within a circular economy. To evaluate this option, our experimental study focused on mixtures’ mechanical responses modelling by the Design of Experiment (DOE) method, consisting of PG from the Jorf Lasfar industrial complex treated with a hydraulic binder (cement C/road hydraulic binder HRB) and a granular corrector (sand S/ phosphate tailings T), meeting mechanical criteria of a subgrade/subbase pavement layer material. To do so, the Proctor test was used to find the optimum water content and dry density, and it was optimized using the same DOE method. In addition, environmental assessment, based on leaching tests measured on two mixtures suitable for each use, showed that all measured heavy metals (Cr, Cd, Pb, Cu, As, Zn, Ni) concentrations were far below international standard limits, due to either encapsulation in the crystalline structure of gypsum or thanks to cement treatment, which enabled trace metals to be fixed through the C–S–H formation. In addition, the mechanical strengths of the mixtures were improved, as shown by SEM and XRD investigations. Finally, a life-cycle analysis, based on industrial software, showed that a pavement structure with a sub-base and subgrade course composed of PG mixes reduces energy and water consumption by 50%, and CO2 emissions by 30%.