DETERMINATION OF SPECIMEN-SIZE INDEPENDENT FRACTURE-TOUGHNESS OF PLAIN CONCRETE

Simple analytical expressions are proposed for determining the critical stress intensity factor and the critical energy release rate of plain concretes in three-point bending. These expressions take into account the slow crack growth preceding fracture and the complex state of stress existing at a propagating crack front. The fracture toughness so determined is shown to be essentially independent of the test specimen dimensions and to depend only on the mix variables.