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X-Ray CT inspection of subsurface areas of concretes exposed to fast flowing liquids
Sitek, Libor ; Hlaváček, Petr ; Souček, Kamil ; Bodnárová, L. ; Foldyna, Josef ; Zajícová, Vendula ; Berčáková, Andrea ; Foldyna, Vladimír
Concrete structures affected for a long time by flowing liquids are exposed to gradual erosion in surface layers caused by a combination of several degradation processes: abrasion, cavitation and chemical or bacterial impacts. Due to the complex phenomena and difficult-to-define initial and boundary conditions, the whole process cannot be easily simulated using the conventional computing tools. Laboratory experimental research is thus the most appropriate approach for the investigation of a suitable composition of concrete resistant to the flowing liquids. However, the methods used are often very time consuming and last even several years. High-speed water flows can be elegantly used for the acceleration of the mechanical simulation of a real situation. Several experiments on the effects of the high-speed water flows on concrete surfaces have been carried out. Using the X-Ray CT methods, subsurface structures of concretes exposed to the accelerated mechanical simulation of the erosion wear caused by fast flowing liquids were investigated and presented in the article. It has been shown that the simulation does not cause initiation of new fractures or cracks in the original concrete structure. The pure water flow mainly removes the hardened cement paste and reveals the aggregate grains. The water flow with abrasive particles disintegrates in greater depths and washes out entire aggregate grains, eventually amputates them and finally smoothens entire surface.
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Effects of Water Jets on CNTs/concrete composite
Foldyna, Vladimír ; Foldyna, Josef
Results of the resistance of carbon nanotubes concrete composite (CNTs/concrete\ncomposite) to the action of pulsating and continuous water jets are presented in\nthis paper. This work brings advanced results of fully hydrated CNTs/concrete\ncomposite (after 28 days) and it follows up the research of this composite\nhydrated 7 days. The experiments were focused at the determination of erosion\neffects of both types of water jets impinging the surface of reference (concrete) and\nCNTs/concrete composite samples. Erosion effects of water jets were evaluated in\nterms of material removal rate. Tests were performed at various operating\nparameters of continuous and pulsating water jets.
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