Using alkali-activated slag ultra-low carbon concrete (AAS-ULCC) for manufacturing segments offers a novel approach to reducing carbon emissions in shield tunnels. However, the inherent high shrinkage and brittleness of AAS-ULCC could potentially impact the safety and durability of tunnel structures. This study focusses on optimising AAS-ULCC to enhance its suitability for segment structures in shield tunnels. Steel fibres were incorporated to prepare steel fibre-reinforced alkali-activated slag ultra-low carbon concrete (SF-AAS-ULCC), and the impact of varying the length and volume fraction (V_f) of steel fibres on the long-term mechanical properties, shrinkage, and durability of AAS-ULCC was systematically investigated. The findings indicate that adding 1.5% V_f of steel fibres significantly reduced the slump of AAS-ULCC. As the V_f of steel fibres increased, there was a corresponding increase in compressive strength, axial compressive strength, splitting tensile strength, flexural strength, and resistance to sulfate attack in SF-AAS-ULCC. Additionally, the failure mode of SF-AAS-ULCC shifted from brittle to multiple-crack ductile failure. Both autogenous and drying shrinkage of SF-AAS-ULCC were reduced. Analysis using X-ray computed tomography (X-CT) and scanning electron microscopy (SEM) revealed that the steel fibres are tightly bonded with the matrix, and the inclusion of steel fibres decreased the porosity of the matrix and effectively inhibited the development of micro-cracks. The research outcomes offer reliable experimental data for promoting the application of AAS-ULCC in segment production, thereby contributing to the reduction of carbon emissions in the tunnel construction sector.

中文翻译：

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钢纤维盾构隧道管片碱活化渣超低碳混凝土 （AAS-ULCC） 的性能优化


将碱活性矿渣超低碳混凝土 （AAS-ULCC） 用于制造段提供了一种减少盾构隧道碳排放的新方法。然而，AAS-ULCC 固有的高收缩率和脆性可能会影响隧道结构的安全性和耐久性。本研究的重点是优化 AAS-ULCC，以提高其对盾构隧道管片结构的适用性。掺入钢纤维制备钢纤维增强碱活性矿渣超低碳混凝土 （SF-AAS-ULCC），系统研究了改变钢纤维长度和体积分数 （VF_{） 对} AAS-ULCC 长期力学性能、收缩率和耐久性的影响。研究结果表明，添加 1.5% V_f 的钢纤维可显著降低 AAS-ULCC 的坍落度。随着钢纤维 VF 的增加，SF-AAS-ULCC 的抗压强度、轴向抗压强度、劈裂拉伸强度、弯曲强度和抗硫酸盐侵蚀能力相应增加。此外，SF-AAS-ULCC 的破坏模式由脆性转变为多裂纹延性破坏。SF-AAS-ULCC 的自体收缩率和干燥收缩率均有所降低。使用 X 射线计算机断层扫描 （X-CT） 和扫描电子显微镜 （SEM） 进行的分析表明，钢纤维与基体紧密结合，钢纤维的加入降低了基体的孔隙率，有效抑制了微裂纹的发展。 研究成果为促进 AAS-ULCC 在管片生产中的应用提供了可靠的实验数据，从而为减少隧道建设领域的碳排放做出贡献。