Study on bending damage and failure of basalt fiber reinforced concrete under freeze-thaw cycles

The whole-field deformation of the basalt fiber reinforced concrete under three-point bending test were measured by the digital image correlation (DIC) technique. Based on the horizontal strain field on the specimen's surface, a damage degree factor and a localization factor were proposed to describe the bending damage and failure characteristics of the specimens, with a further analysis of the effect of the fiber content and freeze-thaw cycles on the characteristics. The experimental results show that the failure process can be divided into three stages: the micro-fracture dispersion, the macro-crack selection, and the main crack propagation. The basalt fiber extended the nonlinear phase of the curves characterizing the two factors, indicating that the fiber enhanced the resistance to the elastic-plastic deformation and thereby restrained the bending damage and failure. The freeze-thaw cycles shortened the linear phase of the two factor curves, suggesting that the freeze-thaw could reduce the elastic deformation capacity of the specimen and thereby accelerate the bending damage process. The incorporation of fibers can reduce the influence of freeze-thaw on the damage and failure process of the specimen, and in this test, the best bending performance of the basalt fiber concrete is given by concrete with 2.0 kg/m3 basalt fiber density, but the freezing and thawing will weaken the role of fiber to inhibit the damage. Both the fiber incorporation and the freezing and thawing can change the bending damage process from the brittle failure to the ductile failure. However, in this process, the fiber incorporation can improve the bending strength of the specimen while the freeze-thaw can reduce the strength.