Experimental Study on Crack Propagation of Concrete Under Various Loading Rates with Digital Image Correlation Method

The quantificational exploration of the propagation law of fracture process zone (FPZ) is of great importance to the research on concrete fracture. This paper performed fracture experiments on pre-cracked concrete beams under various loading rates. Digital image correlation (DIC) method was applied to obtain the whole field displacement of concrete in the fracture test. The crack opening displacement (COD) and the evolution of FPZ were determined based on the whole field displacement. The results show that the length of FPZ first increases and then decreases with the development of the effective crack length and the maximum length of FPZ is about 60 mm. It can be found that the length of FPZ corresponding to the peak load decreases with the increase of loading rates. Based on the fictitious crack model, a bilinear softening model was established. According to the proposed model, the mechanical behavior and the propagation law of FPZ were analyzed. The bilinear softening model can reflect the microcrack development and the aggregate interlocking in the FPZ.