Ultra-high-performance fiber-reinforced concrete (UHPFRC) is an excellent material for harsh environments, but corrosion will change its internal microstructure and complicate the fracture evolution, bringing great difficulties in evaluating the long-term service life. Limited attention has been paid to the fracture mechanism of the UHPFRC upon corrosion. In the present study, integrating acoustic emission (AE) and digital image correlation (DIC) techniques are used to assess the micro/macrocracking characteristics of the specimens upon various corrosion degrees. Results show that the 56-day corroded UHPFRC with 2 vol% presents a remarkable decrease rate of 32%, 29% and 30% in the flexural stiffness, flexural strength and compressive strength. During the loading process, compaction of the original defects induced by fiber corrosion is concentrated in the elastic stage, the newborn cracks triggered by loading mainly occur in the strain-hardening stage, and the expansion of cracks mainly lies in the strain-softening stage. Corroded UHPFRC specimens with higher corrosion damage have a greater maximum strain value at the crack. In addition, the failure mode changes from shear crack failure to a brittle failure of tensile crack as corrosion damage increases. The macroscopic destruction of the corroded UHPFRC is a manifestation of internal microdamage evolution in fiber corrosion and matrix deterioration.

中文翻译：

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超高性能纤维增强混凝土的腐蚀引起的劣化和断裂机制

超高性能纤维增强混凝土（UHPFRC）是一种适用于恶劣环境的优异材料，但腐蚀会改变其内部微观结构，使断裂演化复杂化，给评估其长期使用寿命带来很大困难。对 UHPFRC 腐蚀断裂机制的关注有限。在本研究中，集成声发射（AE）和数字图像相关（DIC）技术用于评估不同腐蚀程度下样品的微观/宏观裂纹特征。结果表明，2 vol%的UHPFRC腐蚀56天后，其弯曲刚度、弯曲强度和压缩强度显着下降，分别为32%、29%和30%。加载过程中，纤维腐蚀引起的原有缺陷的压实集中在弹性阶段，加载引发的新生裂纹主要发生在应变硬化阶段，裂纹的扩展主要发生在应变软化阶段。具有较高腐蚀损伤的腐蚀 UHPFRC 试样在裂纹处具有较大的最大应变值。此外，随着腐蚀损伤的增加，失效模式从剪切裂纹失效转变为拉伸裂纹脆性失效。腐蚀的UHPFRC的宏观破坏是纤维腐蚀和基体劣化内部微观损伤演变的表现。