Abstract: Based on the experiment, the application mode of carbon fiber and the effect of impact load on the mechanical properties of freeze-thaw damaged concrete were investigated. The impact compression tests of four kinds of concrete (plain concrete, carbon fiber concrete, carbon fiber cloth concrete, carbon fiber and fiber cloth concrete) under different loading rates were carried out by using Hopkinson pressure rod (SHPB) after different freeze-thaw cycles (0, 25, 50, 75, 100). The influences of the number of freeze-thaw cycles, carbon fiber reinforcement mode and loading rate on the dynamic stress-strain curve, peak stress, toughness and energy consumption of concrete materials were analyzed. The results show that: ①the peak stress of carbon fiber concrete, carbon fiber cloth concrete and carbon fiber and fiber cloth concrete is 1.30, 1.63, 1.95 times of plain concrete under 0 freeze-thaw cycles and 0.3 MPa impact pressure, both carbon fiber and carbon fiber cloth can effectively improve the dynamic compressive strength of concrete materials, and the lifting effect of carbon fiber cloth is more significant; ②compared with non-freezing-thawing specimens, the peak stress of plain concrete specimens with freezing-thawing cycles of 25, 50, 75 and 100 times decreased by 3.93%, 19.01%, 28.52% and 41.95%, and the peak stress of four kinds of concrete specimens was linearly and negatively correlated with the number of freezing-thawing cycles; ③when the impact pressure was 0.3 MPa and the freeze-thaw cycle was 100 times, the toughness of the samples of carbon fiber and fiber cloth concrete, carbon fiber cloth concrete and carbon fiber concrete was 3.78, 2.44 and 1.81 times that of plain concrete, respectively, carbon fiber and carbon fiber cloth can not only enhance the toughness of the specimen, but also enhance the freezing resistance of the specimen; ④during freeze-thaw cycles of 25, 50, 75 and 100 times, the unit volume dissipative energy of carbon fiber and fiber cloth concrete specimens decreased by 1.70%, 3.64%, 6.07% and 12.14%, respectively, and the unit volume dissipative energy of raw concrete specimens decreased by 21.43%, 35.71%, 53.57% and 73.21%, the presence of carbon fiber has a certain enhancement effect on the freeze-thaw damage resistance of concrete.

Key words: freeze-thaw cycle, impact load, carbon fiber, concrete, dynamic peak stress, toughness, energy dissipation, composites