Comparative study on the dynamic mechanical properties of steel fiber reinforced concrete at high temperatures and after high temperature cooling

The mechanical behaviors of structure concrete can degrade significantly at high temperatures from fire. The mechanical performance of structure concrete may recover to some extent during the subsequent cooling process after fire. A comparative study on the dynamic performance of concrete between at high temperature and after cooling down is necessary to predict dynamic response of structures subjected to fire or blast loads more precisely. In this paper, the dynamic characteristics of Steel Fiber Reinforced Concrete (SFRC) after high temperature cooling were examined with the use of Split Hopkinson Pressure Bar (SHPB) and compared with the test results at high temperature. The dynamic compressive strength, dynamic increase factor (DIF) of stress and peak strain of SFRC with different fiber volume (0%,1%,2%) after natural cooling from different target temperatures (200 ℃, 400 ℃, 600 ℃) to ambient temperature were obtained and compared. Experimental results show that the dynamic compressive strength and peak strain of the specimen first increases and then decreases with the increase of the strain rate cause the high temperature cooling process made the specimens prone to local failure at high strain rates. The mechanical properties of SFRC such as strength can be well recovered during the natural cooling process after high temperature. The deformation capacity and energy dissipation capacity of different types of concrete after high temperature cooling are greatly improved compared with that under high temperatures.