Enhancement of Mechanical Property of Concrete Structure Using the Macro and Micro Steel Fibers

Hybrid fiber reinforcement with both macro and micro steel fibers in the concrete matrix is applied in order to evaluate its effectiveness for crack arresting. One of the main objectives of this research is to establish a crack-free high performance concrete. In severe conditions, which may require high water tightness, such as a storage structure for low-level radioactive waste, crack-free high performance concrete structures could be applied. Hybrid fiber reinforcement is well known because it can show excellent performance with a suitable combination of fibers. In this study which deals with hybrid fiber reinforced concrete made with different fiber lengths and fiber contents, the factors which quantify crack resistance of concrete, mainly the first crack strength, flexural strength and strain energy release rate are examined. In this research, the crack resistance of concrete was investigated using the notched specimen by the 4-point bending test for the fiber reinforced concrete and hybrid fiber reinforced concrete (adding the macro and micro fibers). The general conclusions obtained are as follows. To the investigation of the crack resistance of concrete, we obtained the new theoretical equation of the critical strain energy release rate for the hybrid fiber reinforced concrete, and a deep correlation between experimental value and theoretical value was shown. Though in this research, total fiber contents 2.5% showed the maximum values in the strength and crack resistance, an investigation of the totally mechanical behavior needs more widely range of experiment.