Wear and erosion of concrete structures by high velocity water flow is a basic aspect of the durability of marine and water constructions. The mechanism of concrete failure in such constructions is not well understood. Using high velocity water jets for simulating the loading, the authors observed the general behavior of the material during failure and investigated the influence of water velocity and exposure time. The results show that the interface between hardened cement paste and aggregate grains plays the main role in the fracture process. The basic mechanism of material failure is the generation and propagation of cracks at this interface. It is found that a critical loading intensity, which is characterized by a threshold velocity and a threshold exposure time, must be achieved in order to induce the erosion process. Through mass removal measurements, a mathematical relation between both parameters and the erosion intensity is found. Using a computer program for simulating the hydrodynamics inside a crack, the water pressure and flow velocities in a model crack were calculated.
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