Abstract: To study the performance of concrete fractures, using the line method of the theory of critical distance (TCD), this paper derives functional relationships between generalized critical distance, nominal fracture toughness, and tensile strength of concrete. The results show that the TCD line method can obtain fracture toughness slightly more conservative than that of the double K fracture criterion and it gives an estimated value of the corresponding fracture process zone (FPZ) length. It is applied to an analysis of the fracture toughness and FPZ of geometrically similar concrete beams, and comparison with the unstable fracture toughness obtained using the double K fracture criterion shows the feasibility of the line method.

Key words: concrete, critical distance, fracture toughness, tensile strength, double K fracture criterion, fracture process zone