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<p>Although previous studies have made progress in enhancing the strength and reactivity of phosphogypsum-based cementitious materials (PBCM), current research still predominantly relies on energy-intensive pretreatment methods, while systematic investigations into the synergistic mechanism between phosphogypsum and slag under alkali-activated cremain relatively scarceonditions, as well as the application of phosphogypsum at high dosages,. This study investigates alkali-activated phosphogypsum cementitious material (PBCM), aiming to elucidate its mechanical properties, hydration reaction mechanisms, and applicability in non-fired bricks. By regulating the mass ratio of Na2SO4 to quicklime, the phosphogypsum (PG) -to-slag (SL) ratio, and the activator dosage, the influence of mix design parameters on material properties was systematically investigated. Microstructural and hydration characteristics were analysed using XRD, FT-IR, SEM-EDS, and hydration heat testing. Results indicate that optimal comprehensive properties are achieved when Na2SO4 : quicklime = 1.5:1, PG : SL = 6:4, the activator dosage is 8%, W/B = 0.5, and B/S = 0.33. The 14days strength met the GC 22.5 grade requirement specified in the “Solid waste based cementitious Materials” (T/CECS 10400 − 2024). Additionally, the 28days flexural strength satisfies the standards for grades 32.5 and 32.5R in the “Common portland cement” (GB 175–2023)., with compressive strength only 1.6&#xa0;MPa lower. The hydration process exhibited a three-stage exothermic characteristic, with a cumulative heat release of 954.28&#xa0;J over 96&#xa0;h, corresponding to CaO hydration and SL dissolution, AFt formation, and gel structure strengthening. Non-fired bricks prepared with the optimal mix design achieved the 28 days compressive strength of 8.5&#xa0;MPa, meeting the MU7.5 grade requirements of “Solid concrete brick” (GB/T 21144 − 2023) and the “Code for design of masonry structures” (GB 50003−2011). Furthermore, the leaching concentrations of F-, PO43-, As, and Cr all fell below the limits specified in GB 8978−1996. Research indicates that PBCM holds promising potential in mechanical properties, environmental safety, and engineering applications, providing technical support for PG resource utilization and green building material development.</p>

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Alkali-activated phosphogypsum-slag binders for non-fired brick: performance and microstructural insights

  • 期刊论文

  • 发表日期：

    2026年5月12日

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  • Yan Ying,
  • Sheng-dong Liu,
  • Chao-qiang Wang

摘要

Although previous studies have made progress in enhancing the strength and reactivity of phosphogypsum-based cementitious materials (PBCM), current research still predominantly relies on energy-intensive pretreatment methods, while systematic investigations into the synergistic mechanism between phosphogypsum and slag under alkali-activated cremain relatively scarceonditions, as well as the application of phosphogypsum at high dosages,. This study investigates alkali-activated phosphogypsum cementitious material (PBCM), aiming to elucidate its mechanical properties, hydration reaction mechanisms, and applicability in non-fired bricks. By regulating the mass ratio of Na2SO4 to quicklime, the phosphogypsum (PG) -to-slag (SL) ratio, and the activator dosage, the influence of mix design parameters on material properties was systematically investigated. Microstructural and hydration characteristics were analysed using XRD, FT-IR, SEM-EDS, and hydration heat testing. Results indicate that optimal comprehensive properties are achieved when Na2SO4 : quicklime = 1.5:1, PG : SL = 6:4, the activator dosage is 8%, W/B = 0.5, and B/S = 0.33. The 14days strength met the GC 22.5 grade requirement specified in the “Solid waste based cementitious Materials” (T/CECS 10400 − 2024). Additionally, the 28days flexural strength satisfies the standards for grades 32.5 and 32.5R in the “Common portland cement” (GB 175–2023)., with compressive strength only 1.6 MPa lower. The hydration process exhibited a three-stage exothermic characteristic, with a cumulative heat release of 954.28 J over 96 h, corresponding to CaO hydration and SL dissolution, AFt formation, and gel structure strengthening. Non-fired bricks prepared with the optimal mix design achieved the 28 days compressive strength of 8.5 MPa, meeting the MU7.5 grade requirements of “Solid concrete brick” (GB/T 21144 − 2023) and the “Code for design of masonry structures” (GB 50003−2011). Furthermore, the leaching concentrations of F-, PO43-, As, and Cr all fell below the limits specified in GB 8978−1996. Research indicates that PBCM holds promising potential in mechanical properties, environmental safety, and engineering applications, providing technical support for PG resource utilization and green building material development.