Incorporating carbon nanotubes (CNTs) into concrete can improve its fracture toughness. The crack resistance properties of reinforced concrete with CNTs were tested by ring test and three-point bending beam fracture test. The fracture parameters of reinforced concrete with CNTs were analysed by using double-K fracture parameters and the results showed that CNTs can improve the crack resistance properties. When the CNT content was 0.10 wt%, the compressive strength at 28 days and the splitting tensile strength of concrete were increased by 1.7 and 11.7%, respectively. When the CNT content was 0.15 wt%, the cracking time of concrete under semi-closed and closed conditions was extended by 42.1 and 41.2%, respectively. The initiation fracture toughness, the unstable fracture toughness and the fracture energy of concrete were increased by 31.0, 32.4 and 24.6%, respectively. It was found that CNTs delay the propagation of micro-cracks by bridging across the micro-cracks in concrete and strengthening the interfacial transition zone.

中文翻译：

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碳纳米管改性混凝土的抗裂性能

在混凝土中加入碳纳米管（CNT）可以提高其断裂韧性。通过环形试验和三点弯曲梁断裂试验测试了碳纳米管钢筋混凝土的抗裂性能。采用双K断裂参数对含碳纳米管钢筋混凝土的断裂参数进行了分析，结果表明碳纳米管可以提高抗裂性能。当CNT含量为0.10 wt%时，混凝土的28天抗压强度和劈裂抗拉强度分别提高了1.7%和11.7%。当CNT含量为0.15 wt%时，混凝土在半封闭和封闭条件下的开裂时间分别延长了42.1%和41.2%。混凝土的起始断裂韧性、不稳定断裂韧性和断裂能分别提高了31.0、32。分别为 4% 和 24.6%。发现碳纳米管通过桥接混凝土中的微裂缝并加强界面过渡区来延缓微裂缝的扩展。