Abstract: The freeze-thaw environment will cause damage to concrete materials. Based on the experimental study, the damage evolution law and dynamic mechanical properties of chopped basalt fiber (6 mm) concrete under freeze-thaw cycle are studied. The non-metallic ultrasonic detector is used to measure the longitudinal wave velocity of basalt fiber concrete under different freeze-thaw cycles (0, 25, 50, 75, 100, 125) when the fiber content is 0%, 0.2%, 0.4% and 0.6%. Dynamic uniaxial compression test of chopped basalt fiber concrete with Hopkinson compression bar. The effects of fiber content and freeze-thaw cycles on the quality, longitudinal wave velocity and dynamic mechanical properties of basalt fiber concrete are analyzed. The microstructure of the specimen under freeze-thaw cycle was observed by SEM. Freezing and thawing will cause fatigue damage of concrete materials, peeling damage of material surface, mass reduction and longitudinal wave velocity reduction. The addition of basalt fiber will increase the integrity of the specimen and reduce the fatigue damage of concrete caused by freeze-thaw. The effect is the best when the content is 0.4%. The freeze-thaw cycle reduces the dynamic peak stress, elastic modulus and toughness of the specimen under dynamic load, and increases the peak strain. Under the same freeze-thaw times, the toughness of the specimen increases first and then decreases with the increase of fiber content. SEM test results show that the freeze-thaw cycle will expand the internal cracks of concrete and increase the damage degree, and the addition of fiber will reduce the freeze-thaw damage degree.

Key words: freeze thaw cycle, chopped basalt fiber, mass loss rate, longitudinal wave velocity, toughness, dynamic mechanical properties, scanning electron microscope