The interfacial bonding between steel fibers and Ultra-High Performance Concrete (UHPC) matrix is pivotal for the mechanical properties in extreme environments. Herein, a surface nanoengineering approach using the sol-gel method was reported to enhance the resistance of fiber bonding to varying cryogenic and elevated exposures (−170 °C to 200 °C). Additionally, the interfacial bonding and failure of the steel fiber-matrix interface were evaluated by in-situ acoustic emission (AE) monitoring and a series of microscopic characterizations. The result indicated that the deposition of a nano-SiO₂ coating with a film structure thickness of approximately 150 nm on fiber surface could be achieved. The coating exhibited excellent cryogenic resistance but inferior elevated resistance, as elevated temperatures caused the coating to crack and corrode. After modification, the interfacial bonding stability exposed to thermal variations was enhanced. At ambient temperature, the bond strength of the modified fibers increased by 44.68% compared to before modification, while that increased by 1.54%−13.49% in a single thermal-variations cycle compared to the ambient modified group. Interface enhancement arises from imbalances in nanocoating thermal stability, moisture phase changes, properties of three-phase interface transition zone, and thermal expansion coefficient disparities. Those findings provide new insight into the attempts to improve the mechanical and durability properties of concrete under extreme temperature environments.

中文翻译：

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用于 UHPC 的纳米工程钢纤维：不同低温和高暴露的影响


钢纤维和超高性能混凝土 （UHPC） 基体之间的界面粘合对于极端环境下的机械性能至关重要。在此，据报道，一种使用溶胶-凝胶方法的表面纳米工程方法可以增强纤维键合对不同低温和高曝光（-170 °C 至 200 °C）的抵抗力。此外，通过原位声发射 （AE） 监测和一系列微观表征评估了钢纤维-基体界面的界面结合和失效。结果表明，可以在纤维表面沉积薄膜结构厚度约为 150 nm 的纳米 SiO₂ 涂层。该涂层表现出优异的耐低温性，但耐高温性较差，因为高温会导致涂层开裂和腐蚀。改性后，暴露于热变化下的界面键合稳定性得到增强。在环境温度下，改性纤维的粘结强度比改性前提高了 44.68%，而与环境改性组相比，在单个热变周期内提高了 1.54%−13.49%。界面增强源于纳米涂层热稳定性、水分相变、三相界面过渡区特性和热膨胀系数差异的不平衡。这些发现为尝试在极端温度环境下改善混凝土的机械和耐久性提供了新的见解。