While self-consolidating concrete (SCC) has emerged as a highly effective approach for the repair of concrete structures, there have been few investigations regarding the effect of the combination of different fiber and shrinkage-mitigating material types (shrinkage-reducing admixture, SRA; superabsorbent polymer, SAP; and expansive agent, EA) on the flexural behavior of repaired structures. This study aims to explore the influence of three different shrinkage-mitigating materials (1.25%–2.5 % SRA, 4%–8% EA, and 0.2%–0.4 % SAP), four fiber types (two macro synthetic fibers, MSFA and MSFB; 5D hooked steel fibers, 5D; a combination of 80 % 3D hooked steel +20 % short steel fibers STST) on fresh and hardened properties, cement hydration, and drying shrinkage of fiber-reinforced self-consolidating concrete (FR-SCC). Specifically, the effect of different shrinkage-mitigating materials, fiber types, and two repair thicknesses corresponding to 1/3 and 2/3 of the total height of prismatic element on the flexural performance of composite specimens repaired using FR-SCC was studied. The bond strength between existing concrete and FR-SCC was also investigated to reveal the flexural behavior of the composite beams. The results indicate that prismatic specimens repaired with FR-SCC made with 1.25 % SRA showed excellent flexural performance compared to those repaired using FR-SCC made with 4%–8% EA and 0.2%-0.4%SAP. The adverse effect of the incorporation of 4%–8% EA and 0.2%–0.4 % SAP on flexural behavior of repair specimens can be attributed to a lower existing concrete-FR-SCC interfacial and fiber-matrix bond strengths. Using SRA, EA, or SAP in FR-SCC improved bond strength with substrate by 10%–60 % compared to FR-SCC without any shrinkage-mitigating materials. The use of 1.25 % SRA showed the highest bond strength, which increased by 10%–37 % and 33%–44 %, respectively, compared to that made with SAP and EA. As the increase in the repair thickness of specimens, the incorporation of SRA, EA, or SAP had different efficiencies to enhance the flexural toughness and residual strength of the repair specimens. Furthermore, the incorporation of 5D fiber and 1.25 % SRA in SCC showed excellent flexural performance, followed by MSFA, STST, and MSFB fibers. The increase in the repair thickness from 1/3 to 2/3 of the total height of the composite beam enhanced the flexural toughness and residual strength by a maximum of 133 % and 160 %, respectively, attributing to fiber type and the increase in fiber volume at the cross-section of specimens.

中文翻译：

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收缩缓解材料、纤维类型和修复厚度对纤维增强自密实混凝土修复梁弯曲行为的影响


虽然自密实混凝土 （SCC） 已成为修复混凝土结构的一种非常有效的方法，但很少有关于不同纤维和收缩缓解材料类型（减少收缩外加剂，SRA;高吸水性聚合物，SAP;和膨胀剂，EA）的组合对修复结构弯曲性能的影响的研究。本研究旨在探讨三种不同收缩缓解材料（1.25%–2.5% SRA、4%–8% EA 和 0.2%–0.4% SAP）、四种纤维类型（两种宏观合成纤维、MSFA 和 MSFB;5D 钩状钢、5D;80% 3D 钩状钢 +20% 短钢纤维 STST 的组合）对新鲜和硬化性能、水泥水化、 以及纤维增强自密实混凝土 （FR-SCC） 的干燥收缩率。具体来说，研究了不同收缩缓解材料、纤维类型以及对应于棱柱单元总高度的 1/3 和 2/3 的两种修复厚度对使用 FR-SCC 修复的复合材料试件弯曲性能的影响。还研究了现有混凝土和 FR-SCC 之间的粘合强度，以揭示组合梁的弯曲行为。结果表明，与使用 4%–8% EA 和 0.2%-0.4% SAP 的 FR-SCC 修复的样品相比，用 1.25% SRA 制成的 FR-SCC 修复的棱柱形试样表现出优异的弯曲性能。掺入 4%–8% EA 和 0.2%–0.4% SAP 对修复试样弯曲性能的不利影响可归因于较低的现有混凝土-FR-SCC 界面和纤维-基体粘合强度。与没有任何收缩缓解材料的 FR-SCC 相比，在 FR-SCC 中使用 SRA、EA 或 SAP 将与基材的粘合强度提高了 10%-60%。用途 1.25% SRA 显示出最高的粘合强度，与 SAP 和 EA 相比，分别提高了 10%-37% 和 33%-44%。随着试件修复厚度的增加，SRA 、 EA 或 SAP 的掺入具有不同的效率，以提高修复试件的弯曲韧性和残余强度。此外，在 SCC 中掺入 5D 纤维和 1.25% SRA 显示出优异的弯曲性能，其次是 MSFA、STST 和 MSFB 纤维。修复厚度从复合梁总高度的 1/3 增加到 2/3，弯曲韧性和残余强度分别提高了 133 % 和 160 %，这是由于纤维类型和试样横截面纤维体积的增加。