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<p>This study develops an innovative approach for phosphogypsum (PG) valorization through a two-stage calcination process to produce modified PG (MPG). The thermal treatment effectively eliminates residual acidic impurities while optimizing particle size distribution and phase composition, significantly enhancing the material’s cementitious properties. On this basis, a novel all-solid-waste cementitious material (PGSC) by integrating modified PG (50 wt%) with ground granulated blast-furnace slag (GGBS, 40 wt%) and steel slag (SS, 10 wt%) was proposed, where sodium hydroxide (NaOH) served as an efficient alkaline activator. NaOH activation facilitates the dissolution of silica-alumina phases from GGBS/SS, enabling synergistic formation of ettringite (AFt) and calcium silicate hydrate (C-S-H) gel through reaction with Ca<sup>2+</sup> liberated from MPG. The PGSC with 2.00 wt% NaOH achieved remarkable 3-day and 28-day compressive strengths of 30.5&#xa0;MPa and 56.8&#xa0;MPa, respectively. Under hyperalkaline conditions, the excessive formation of AFt crystals compromised structural integrity, triggering microcrack development and consequent strength reduction. Microstructural analysis identified AFt and C-S-H gel as the dominant hydration phases, whose interpenetrating network architecture governed the macroscopic mechanical behavior. This work provides a high-efficiency solution that addresses solid waste recycling, demonstrating significant potential for developing eco-friendly cementitious materials with industrial byproducts.</p>

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Recycling phosphogypsum through two-stage calcination modification: development of high-performance all-solid-waste cementitious materials

  • 期刊论文

  • 发表日期：

    2025年11月22日

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  • Gaofeng Peng,
  • Xiantao Qin,
  • Siyue Zhu,
  • Xin Wang,
  • Junkun Zhang,
  • Yuhao Wu,
  • Zhihao Liu,
  • Bo Hu,
  • Jin Huang

摘要

This study develops an innovative approach for phosphogypsum (PG) valorization through a two-stage calcination process to produce modified PG (MPG). The thermal treatment effectively eliminates residual acidic impurities while optimizing particle size distribution and phase composition, significantly enhancing the material’s cementitious properties. On this basis, a novel all-solid-waste cementitious material (PGSC) by integrating modified PG (50 wt%) with ground granulated blast-furnace slag (GGBS, 40 wt%) and steel slag (SS, 10 wt%) was proposed, where sodium hydroxide (NaOH) served as an efficient alkaline activator. NaOH activation facilitates the dissolution of silica-alumina phases from GGBS/SS, enabling synergistic formation of ettringite (AFt) and calcium silicate hydrate (C-S-H) gel through reaction with Ca2+ liberated from MPG. The PGSC with 2.00 wt% NaOH achieved remarkable 3-day and 28-day compressive strengths of 30.5 MPa and 56.8 MPa, respectively. Under hyperalkaline conditions, the excessive formation of AFt crystals compromised structural integrity, triggering microcrack development and consequent strength reduction. Microstructural analysis identified AFt and C-S-H gel as the dominant hydration phases, whose interpenetrating network architecture governed the macroscopic mechanical behavior. This work provides a high-efficiency solution that addresses solid waste recycling, demonstrating significant potential for developing eco-friendly cementitious materials with industrial byproducts.