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Crack resistance property of carbon nanotubes-modified concrete

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 analyzed by using double-K fracture parameters, and the results showed that CNTs can improve the crack resistance concrete properties. When the content of CNTs was 0.10wt%, the compressive strength at 28 days and splitting tensile strength of concrete were increased by 1.7% and 11.7%, respectively. When the content of CNTs was 0.15wt%, the cracking time of concrete under the 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.