An investigation of the effects of mix strength on the fracture and fatigue behavior of concrete mortar

This paper examines the effects of mix compressive strength (30, 35 and 40 MPa) on the fracture initiation toughness, resistance-curve behavior and fatigue crack growth behavior of concrete mortar. The fracture initiation toughness and the resistance-curve behavior are shown to increase with increasing mix strength. The observed resistance-curve behavior is then attributed largely to the effects of ligament bridging, which are predicted using small- and large-scale bridging models. In contrast, the fatigue crack growth resistance is shown to decrease with increasing mix strength. An extended multiparameter framework was used for the modeling of fatigue crack growth. Finally, the implications of the results are discussed for the design of concrete mixtures with attractive combinations of strength, fracture toughness and fatigue crack growth resistance.