Carbon nanotubes⁃carbon fiber composite reinforcement (CNTs⁃CF) is a new fiber material assembled by grafting carbon nanotubes (CNTs) on the surface of carbon fiber (CF) . The idea of the cross⁃scale modification of concrete by CNTs⁃CF was proposed. Five kinds of carbon nanotubes⁃carbon fiber composite modified concrete (CCMC) with different volume content of CNTs⁃CF (0%, 0.1%, 0.2%, 0.3% and 0.4%) were prepared. The compressive strength, flexural strength, flexure compression ratio (the ratio of flexural strength to compressive strength), and failure mode of CCMC were tested, and then, according to the scanning electron microscope (SEM) images, the enhancement mechanism of CNTs⁃CF on the basic mechanical properties of concrete was analyzed. The results show that the addition of proper content of CNTs⁃CF in concrete is beneficial to the improvement of compressive strength and flexural strength, and the volume content of CNTs⁃CF in the concrete matrix has a relatively optimal value. Compared with the plain concrete without CNTs⁃CF, when the volume content of CNTs⁃CF is 0.3%, the compressive strength of CCMC increases by 8.79%, and the flexural strength increases by 27.76%. In the range of fiber content in this test, the flexure compression ratio of CCMC shows an increasing trend with the increase of CNTs⁃CF volume content, with an increase rate of 8.47%—19.16%. The addition of CNTs⁃CF can weaken the brittle failure characteristics of concrete. Moreover, when the concrete fails under load, it can still maintain a certain degree of integrity, which is damaged but not scattered and cracked. The surface roughness and specific surface area of CNTs⁃CF are significantly increased, which makes it show more superior strengthening and toughening effect than the original CF. CNTs and CF, which constitute CNTs⁃CF, can give full play to their modification advantages at the nano and micro levels respectively. At the same time, CNTs and CF can cooperate and complement each other, so as to improve the microstructure of concrete and effectively strengthen its mechanical properties. © 2023 Cailiao Daobaoshe/ Materials Review. All rights reserved.
