Energy Transformation in the Fracture Process of Concrete

Abstract

Fracture process of concrete in compression and in flexure was investigated in terms of an energy transfer concept. Reversible and irreversible energies in the fracture process were calculated from the load-deformation diagrams. The reversible strain energy of the concrete specimens becomes largest around the maximum load. Two types of irreversible dissipating energies, Ecᵣₐc consumed by crack formation and Efᵣᵢc consumed by viscous friction, under various water contents were calculated. When a concrete specimen is loaded repeatedly in high compression, the energy Ecᵣₐc, consumed by the crack formation in the first load repetition, becomes larger as the water contents of the concrete decrease. Crack growth from a notch in a beam under a flexural load was closely related with the irreversible dissipating energy. The crack growth from a notch is proportional to the energy dissipation in the beam. Therefore, the dissipating energy calculated from the load-deformation diagrams would be used as an index of damage due to the crack formation in concrete. Propagating cracks in a beam were located by detecting the acoustic emissions.