Mechanical properties of carbon fiber reinforced concrete (CFRC) after exposure to high temperatures

This paper presents an experimental investigation on the residual mechanical properties and microstructure of carbon fiber reinforced concrete (CFRC) after high temperatures. Seven different concrete mixtures with various carbon fiber contents and carbon fiber lengths were prepared. The effects of carbon fiber contents and carbon fiber lengths on the compressive, flexural, and splitting strength of CFRC after high temperatures were systematically reported and analyzed. Besides, the microstructure and carbon fiber failure mode of the fracture plane of CFRC were observed by scanning electron microscopy (SEM). Experimental results demonstrate that the addition of carbon fibers can effectively improve the flexural and splitting strength of CFRC, while the enhancement amplitude of compressive strength is quite limited. The optimum dosages of carbon fiber contents and carbon fiber length are 1.0 wt% and 10 mm, respectively, in terms of the mechanical properties of CFRC after high temperatures. The carbon fiber contents exert the largest influence on the flexural strength of CFRC, followed by the splitting and compressive strength. However, the carbon fiber length negligibly influences the compressive, flexural, and splitting strength of CFRC. The residual ratios of compressive, flexural, and splitting strength of CFRC after high temperatures primarily depend on the rising temperature. The SEM results show that the failure mode of CFRC under loading is mainly the breakage and pullout of the carbon fiber.