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<p>Ultra-high performance concrete (UHPC) typically relies on high cement/clinker content, leading to elevated cost and environmental burdens. This study develops a lower-carbon UHPC by (i) reducing cement demand through partial cement replacement with gold tailings (GT, 10%–30% by mass) and (ii) externally incorporating pre-wetted coal gangue ceramsite (CGC, 200–600&#xa0;kg/m<sup>3</sup>) as a porous aggregate providing internal curing. Workability, mechanical properties, autogenous deformation, heavy-metal leaching, and microstructure (SEM) were investigated, together with a life cycle assessment (LCA) per 1 m<sup>3</sup> of UHPC. Increasing GT replacement and CGC content decreased flowability. At 28 d, GT replacement reduced compressive strength, reaching a 20.01% drop at 30% GT; when CGC was added to the 20% GT mixture, compressive strength slightly increased at moderate dosages (maximum + 2.76%), while flexural strength decreased with CGC addition. GT markedly mitigated autogenous shrinkage (up to 51.44% reduction), and mixtures with pre-wetted CGC and an expansive agent exhibited a late-age net expansion tendency. Leaching concentrations of Mn and Ba were far below regulatory limits (Mn ≤ 0.027 5&#xa0;mg/L; Ba ≤ 0.235 6&#xa0;mg/L). LCA results indicate that T2C4 (chosen as a balanced option within the investigated design space) reduces global warming potential by 32.95% and lowers non-renewable energy demand by 31.34% relative to the reference UHPC. Overall, GT directly reduces cement consumption, and CGC, when normalized to a 1 m<sup>3</sup> functional unit, can partially replace conventional constituents, offering additional potential for clinker and carbon reduction within the defined cradle-to-gate boundary.</p>

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Lower-carbon UHPC incorporating gold tailings and coal gangue ceramsite: strength, shrinkage, and environmental performance

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月13日

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  • Chuanxi Li,
  • Jianfeng Li,
  • Shuai Deng,
  • Zhenhai Zeng,
  • Jinshi Dong

摘要

Ultra-high performance concrete (UHPC) typically relies on high cement/clinker content, leading to elevated cost and environmental burdens. This study develops a lower-carbon UHPC by (i) reducing cement demand through partial cement replacement with gold tailings (GT, 10%–30% by mass) and (ii) externally incorporating pre-wetted coal gangue ceramsite (CGC, 200–600 kg/m3) as a porous aggregate providing internal curing. Workability, mechanical properties, autogenous deformation, heavy-metal leaching, and microstructure (SEM) were investigated, together with a life cycle assessment (LCA) per 1 m3 of UHPC. Increasing GT replacement and CGC content decreased flowability. At 28 d, GT replacement reduced compressive strength, reaching a 20.01% drop at 30% GT; when CGC was added to the 20% GT mixture, compressive strength slightly increased at moderate dosages (maximum + 2.76%), while flexural strength decreased with CGC addition. GT markedly mitigated autogenous shrinkage (up to 51.44% reduction), and mixtures with pre-wetted CGC and an expansive agent exhibited a late-age net expansion tendency. Leaching concentrations of Mn and Ba were far below regulatory limits (Mn ≤ 0.027 5 mg/L; Ba ≤ 0.235 6 mg/L). LCA results indicate that T2C4 (chosen as a balanced option within the investigated design space) reduces global warming potential by 32.95% and lowers non-renewable energy demand by 31.34% relative to the reference UHPC. Overall, GT directly reduces cement consumption, and CGC, when normalized to a 1 m3 functional unit, can partially replace conventional constituents, offering additional potential for clinker and carbon reduction within the defined cradle-to-gate boundary.