Experimental method for determining the fracture toughness of concrete based on the modified two-parameter model and DIC technique

An experimental method, based on the modified two-parameter model and digital image correlation technique, was proposed for determining the mixed mode fracture toughness (KI+II) of concrete. Three-point bending tests on notched concrete beam specimens of different sizes, maximum aggregate sizes, and aggregate volume contents were conducted, and the values of KI+II were evaluated considering the crack deflection. The values of KI+II and K-I under mode I loading were compared. The results show that KI+II increases with the specimen size and gradually stabilizes. In addition, KI+II decreases with the maximum aggregate size, but the aggregate volume content has little effect on KI+II. Higher values of KI+II are presented after considering the effect of crack deflection. Only a monotonic loading process is required for the proposed method to determine KI+II.