\ - - Accelerated High Spee { Watei Erosion Test for Conc Wear Debris Analysiso

Since concrete is used for marine and hydraulic structures, pipe coatings and channel walls, its wear due to the attack of fast flowing water is a problem (1). The first systematic investigations on the resistance of concrete against wear in marine structures were carried out in the 1940s (2). Investigations carried out in the fields of water flow erosion, cavitation and abrasion have been reviewed in Refs. (-7) , (4)' Momber et al. (J)-(10) investigated the inf luences of interfaces, cracks, and inclusions on the failure of brittle multiphase materials due to fast flowing water attack at velocities up to 450 m/s. The predominant mechanisms of the material failure are propagation and intersection of pre-existing microcracks. It was found that the destruction process due to the water flow is introduced in the interface between the matrix and inclusions which are characterized by a high degree of porosity and pre-existing microcracks. The water is pressurized inside a crack; this leads to forces acting on the crack wall surfaces. If thg generated stresses exceed critical material values, e.g., critical stress intensity factor, the crack starts to grow. The crack growth is controlled by the interaction between crack and aggregate grains. It was experimentally shown that inclusions in the material may act as crack arrestors and energy dissipators (8). The intersection of several single cracks leads to a macroscopical material removal. The model is illgstrated in Fig. l. In advanced versions of the phenomenological model, a comPuter-based simula-