Strength deterioration and crack dilation behavior of BFRC under dynamic fatigue loading

Abstract

To simulate the dynamic traffic loads imposed on the concrete during service, a piece of self-designed dynamic loading equipment was used to study the strength deterioration pattern of basalt fiber reinforced concrete (BFRC) under fatigue loading at 0.5 and 0.7 stress levels. Subsequently, crack images of the fracture surface and interior were obtained with a high-pixel camera and SEM, respectively, from which the fractal dimension of the cracks was finally obtained by processing and calculating with MATLAB, Image-Pro Plus, and Fractalfox software. The results showed that, at 0.5 and 0.7 stress levels, the flexural strengths of both BFRC and the reference concrete gradually decreased with increasing number of load actions, but the higher stress caused a faster decrease. Significantly, the flexural strength of BFRC consistently dropped more slowly than that of the reference concrete. The reduction rate of flexural strength of basalt fiber reinforced concrete was reduced by 2.26% and 5.28% compared with the reference group after 200,000 times at 0.5 and 0.7 stress levels, respectively. The maximum crack length, average crack width and crack area density of fiber concrete decreased by 8.81%, 10.69% and 42.29%, respectively, after 200,000 cycles of dynamic fatigue loading at low-stress level compared to the reference concrete. Fatigue loading with high-stress level accelerates the rate of structural deterioration within the concrete, but basalt fibers improve the fatigue performance of concrete by synergistically stressing it with concrete, changing the direction of crack development and extending the crack expansion path. The flexural strength at low-stress level is significantly negatively correlated with the average crack width, while the flexural strength at high-stress level is significantly correlated with the fractal dimension of cracks, crack area density and average crack width.