Fracture of model concrete: 2. Fracture energy and characteristic length

The specific fracture energy GF was measured in six types of simple concrete: all from the same matrix. The aggregates were spheres of the same diameter (strong aggregates, that debonded during concrete fracture, and weak aggregates, able to break); three kinds of matrix–aggregate interface (weak, intermediate and strong) were used. All in all, 55 test results are reported. These results are intended to be used as an experimental benchmark for checking numerical models of concrete fracture. A meso-level analysis of these results showed a correlation between the measured GF values and the properties of the matrix, aggregates and interfaces, particularly with the actual area of the fracture surface. The strength of the matrix–aggregate interface correlates quite well with GF, and concrete ductility, measured by means of the characteristic length, correlates also with the strength of the matrix–aggregate interface.