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<p>This study investigates the valorization of phosphogypsum (PG) as a sustainable additive in bentonite-hydrated lime (HL) based wall coatings. The mineralogical (XRD) and microstructural (SEM/EDS) evolution, unconfined compressive strength (UCS), thermal properties (conductivity, λ, and diffusivity, α), and hydraulic permeability (K) of hardened mortars were evaluated. A Box-Behnken experimental design was employed to model the influence of bentonite, HL, and PG contents. The derived quadratic models exhibited high predictive reliability, with R<sup>2</sup> values of 0.859 for UCS, 0.952 for λ, and 0.984 for α. Results demonstrated that incorporating 16 wt% HL reduced λ and α by 20% and 23%, respectively, due to calcium silicate hydrate (C-S-H) formation. A subsequent addition of 16 wt% PG further enhanced these reductions to 36% and 26%, attributed to ettringite formation and increased porosity. Hydraulic permeability decreasing from 5.45 × 10<sup>− 10</sup> cm s<sup>− 1</sup> (raw bentonite) to 2.27 × 10<sup>− 10</sup> cm s<sup>− 1</sup> for the blend with 8 wt% HL and 8 wt% PG after 181 days. Furthermore, this formulation effectively immobilized heavy metals (Cd, Pb, As, Ni), as confirmed by ICP-MS leachate analysis, ensuring environmental safety through sorption, co-precipitation, and encapsulation within C-S-H and ettringite phases. The findings underscore PG’s potential for developing eco-efficient, thermally insulating, and durable construction materials.</p> Graphical abstract <p></p>

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Phosphogypsum-stabilized bentonite-lime wall coatings: multi-response optimization for thermal performance, durability, and environmental safety

  • 期刊论文

  • 发表日期：

    2026年4月22日

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  • Achraf Harrou,
  • Abdelilah Ayad,
  • Abdelouassia Dira,
  • Othmane Horma,
  • Imane Amar,
  • Meriam El Ouahabi,
  • Rachid Hakkou,
  • ElKhadir Gharibi

摘要

This study investigates the valorization of phosphogypsum (PG) as a sustainable additive in bentonite-hydrated lime (HL) based wall coatings. The mineralogical (XRD) and microstructural (SEM/EDS) evolution, unconfined compressive strength (UCS), thermal properties (conductivity, λ, and diffusivity, α), and hydraulic permeability (K) of hardened mortars were evaluated. A Box-Behnken experimental design was employed to model the influence of bentonite, HL, and PG contents. The derived quadratic models exhibited high predictive reliability, with R2 values of 0.859 for UCS, 0.952 for λ, and 0.984 for α. Results demonstrated that incorporating 16 wt% HL reduced λ and α by 20% and 23%, respectively, due to calcium silicate hydrate (C-S-H) formation. A subsequent addition of 16 wt% PG further enhanced these reductions to 36% and 26%, attributed to ettringite formation and increased porosity. Hydraulic permeability decreasing from 5.45 × 10− 10 cm s− 1 (raw bentonite) to 2.27 × 10− 10 cm s− 1 for the blend with 8 wt% HL and 8 wt% PG after 181 days. Furthermore, this formulation effectively immobilized heavy metals (Cd, Pb, As, Ni), as confirmed by ICP-MS leachate analysis, ensuring environmental safety through sorption, co-precipitation, and encapsulation within C-S-H and ettringite phases. The findings underscore PG’s potential for developing eco-efficient, thermally insulating, and durable construction materials.

Graphical abstract