Study on the durability and mechanical properties of carbon fiber reinforced concrete for shaft lining under chloride salt freeze-thaw coupling environment

Deep mining shaft lining concrete structures are subjected to long-term exposure to complex environments, posing a severe threat to concrete durability. In this paper, static mechanical properties of concrete with different carbon fiber (CF) contents are tested, and the optimal carbon fiber content concrete is selected. Carbon fiber reinforced concrete (CFRC) and ordinary concrete (OC) were immersed in chloride solution for different freeze-thaw cycles, and dynamic and static mechanical properties tests were carried out to study the mechanical properties and deterioration mechanism of CFRC under chloride freeze-thaw coupling environment. The results show that when the carbon fiber content is 0.4%, the comprehensive performance of CFRC is the best. The compressive strength of the specimen is 15.02% higher than that of the reference concrete, and the splitting tensile strength is increased by 51.12%. With the increase of the number of freeze-thaw cycles, the degree of damage and deterioration of the specimens increased, the mass loss rate showed an increasing trend, and the strength increased first and then decreased. When the number of freeze-thaw cycles is 25 cycles, the strength of OC and CFRC reaches the maximum value, which is 44.3MPa and 50.3MPa respectively. The mechanical properties of concrete decrease with the increase of freeze-thaw cycles, and carbon fiber can effectively resist chloride erosion and freeze-thaw damage.