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<p>This study addresses the critical challenges posed by large-scale phosphogypsum stockpiling, which not only exacerbates environmental pollution but also induces significant compressive strength degradation in cement-based backfills because of impurity-mediated hydration retardation. A novel alkali-activated phosphogypsum-based cementitious backfill was developed via response surface methodology (RSM) optimization, employing slag and quicklime as alkaline solid waste substitutes for cement. Microstructural characterization of hydration products was conducted using SEM-EDS and XRD to analyze phase composition and morphological evolution. Experimental results demonstrate that single quicklime addition reduces slurry fluidity and bleeding rate, whereas slag incorporation enhances fluidity while decreasing bleeding. The RSM-derived regression model exhibited excellent accuracy and reliability, with the multi-objective-optimized mix ratio determined as 8.6% quicklime, 12% slag, and 4% cement. Mechanistic analysis reveals that the combined addition of quicklime and slag promotes the formation of C-(A)-S-H gel and ettringite, whose hydration products fill interparticle pores, significantly improving the densification of alkali-activated phosphogypsum-based backfills. This approach not only mitigates environmental burdens of industrial waste but also provides a sustainable solution for high-performance cementitious backfill preparation with enhanced microstructural compactness.</p>

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Optimized Design and Preparation of Alkali-Activated Phosphogypsum-Based Cementitious Filling Materials via Response Surface Methodology

  • 期刊论文

  • 发表日期：

    2025年12月19日

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  • Chengliang He,
  • Mingqing Zhang,
  • Chen Wang,
  • Zhengbin Deng,
  • Yi Luo,
  • Zuming Deng

摘要

This study addresses the critical challenges posed by large-scale phosphogypsum stockpiling, which not only exacerbates environmental pollution but also induces significant compressive strength degradation in cement-based backfills because of impurity-mediated hydration retardation. A novel alkali-activated phosphogypsum-based cementitious backfill was developed via response surface methodology (RSM) optimization, employing slag and quicklime as alkaline solid waste substitutes for cement. Microstructural characterization of hydration products was conducted using SEM-EDS and XRD to analyze phase composition and morphological evolution. Experimental results demonstrate that single quicklime addition reduces slurry fluidity and bleeding rate, whereas slag incorporation enhances fluidity while decreasing bleeding. The RSM-derived regression model exhibited excellent accuracy and reliability, with the multi-objective-optimized mix ratio determined as 8.6% quicklime, 12% slag, and 4% cement. Mechanistic analysis reveals that the combined addition of quicklime and slag promotes the formation of C-(A)-S-H gel and ettringite, whose hydration products fill interparticle pores, significantly improving the densification of alkali-activated phosphogypsum-based backfills. This approach not only mitigates environmental burdens of industrial waste but also provides a sustainable solution for high-performance cementitious backfill preparation with enhanced microstructural compactness.