Interfacial and subinterfacial fracture in concrete

Abstract Interfaces with high and low adhesion have been introduced between old and new concrete. The propagation of bulk, interfacial and subinterfacial cracks has been studied in a split-cube geometry. A crack along a smooth, imperfectly adhering interface propagates easily, a crack along an interface with better adhesion not so easily. Subinterfacial cracks branch off towards the interfaces and consume during that kinkings almost as much energy as bulk cracks. Only cracks closer to the interface than a critical distance kink towards the interface. If further away theyr branch off into the bulk. This critical distance depends on the cohesion of the interface: high cohesive interfaces attract cracks less easily than low cohesive ones. Fractography shows that interfacial cracks open up and weaken the specimen before the original crack reaches the interface.