Abstract The three-point bending tests of concrete specimens at different temperature levels (20 ℃, 0 ℃, −20 ℃, and −40 ℃) were performed using a low-temperature fracture test system. The 3D digital image correlation (3D-DIC) technique was employed to measure the surface deformations of the beams during fracture process. Combined with the displacement fields obtained from 3D-DIC, the crack propagation lengths and crack widths at different loading points were determined, providing information for the fracture process zone (FPZ) evolution in concrete at different temperatures. The results revealed that temperature has significant effect on the crack propagation, i.e. the average FPZ length in the later stage of unloading and the critical crack length ac decrease with decreasing temperature. In addition, the FPZ length for specimens at 0 ℃, −20 ℃ and −40 ℃ decreases slowly in the initial stage and then decreases significantly when the crack extends to the specimen boundary.

中文翻译：

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不同低温下混凝土FPZ演化的3D-DIC实验研究

摘要 采用低温断裂试验系统对不同温度水平（20 ℃、0 ℃、-20 ℃、-40 ℃）的混凝土试件进行三点弯曲试验。采用 3D 数字图像相关 (3D-DIC) 技术测量断裂过程中梁的表面变形。结合从 3D-DIC 获得的位移场，确定了不同加载点的裂纹扩展长度和裂纹宽度，为混凝土在不同温度下的断裂过程区 (FPZ) 演化提供信息。结果表明，温度对裂纹扩展有显着影响，即卸载后期的平均FPZ长度和临界裂纹长度ac随着温度的降低而减小。此外，试样在 0 ℃时的 FPZ 长度，