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Usability of hig speed water jet in civil engineering
Boucníková, Veronika ; Sitek,, Libor (referee) ; Bodnárová, Lenka (advisor)
The bachelor thesis deals with possibilities of using high-speed water jet in construction industry. In the theoretical part, water jet technology was generally described and a research for use in the construction industry with an emphasis on the application of concrete structures redevelopment and the process of interaction of water jet with concrete was done. Furthermore, the safety risks during work with high-speed water jet and the possibilities of recycling of waste generated by the use of this technology were evaluated. In the experimental part were prepared concrete samples with dispersed concrete reinforcement. The characteristics of the concrete samples were determined and the depth and appearance of the cross-section after interaction with the high-speed water jet was evaluated.
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The issue of concrete resistance to high temperatures
Krejčík, Jakub ; Hela, Rudolf (referee) ; Bodnárová, Lenka (advisor)
Bachelor´s thesis deals with resistance of cement concrete to high temperatures. Theoretical part of bachelor´s thesis describes changes that occures in concrete at thermal loading and behavior of each component of concrete. Next there were discribed ways to improve resistance of concrete to high temperatures, by choosing the right component or by adding fibre reinforcement. In experimental part composites with bassalt and polypropylen fibre and with bassalt aggregates were tested. In these composites changes of compressive strenght and changes of density were mesured according to the thermal loading. Next individual fibre reinforcement polypropylen, celulose and bassalt fibres were exposed to the thermal loading and their changes were observed.
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Dispersed reinforcement influence on the maturation of polymercement materials
Zaťko, Petr ; Jakubík, Aleš (referee) ; Bydžovský, Jiří (advisor)
The diploma thesis is focused on polymercement materials with dispersed reinforcement. The aim of this work is development of suitable polymercement mixture and monitoring of the impact of dispersed reinforcement on the course of maturation of these materials and physico-mechanical properties. The effect of high temperatures on the properties of the mortar is also examined. Emphasis is placed on the use of alternative resources and byproducts. Mixed binder of cement and slag and admixture of microsilica was used. Recycled cellulose was used as dispersed reinforcement and was compared with commercial polypropylene fibers.
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The development of composite material system with focus on matrix for extreme conditions
Gratclová, Kamila ; Gross,, Tomáš (referee) ; Bydžovský, Jiří (advisor)
The thesis deals with composite systems, with a focus on matrix resistant to extreme conditions. The aim of this work was to research and development matrix, resistant to high temperatures, typical in case of fire. Used theoretical knowledge were realized with subsequent laboratory research. Attention was paid matrices based binder mixed with any alkali activation of alternative raw materials and geopolymers. Scattered reinforcement featured polypropylene fibers. The subject of the practical part of the two alternatives, including a matrix based on basic ingredients - cement, alternative raw materials - high fly ash, blast furnace slag, geopolymer and polymeric components incl. combinations thereof. Laboratory research conducted by determining the fundamental material properties such as density, strengths, etc., after heat exposure. The developed materials were subjected to a temperature 1400 ° C. The conclusion was selected several recipes that were based on the resulting values found to be optimal.
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RESEARCH AND DEVELOPMENT COMPOSITE MATERIAL WITH A HIGHER RESISTANCE TO HIGH TEMPERATURES
Válek, Jaroslav ; Durica,, Tibor (referee) ; Kolář,, Karel (referee) ; Sitek,, Libor (referee) ; Bodnárová, Lenka (advisor)
Concrete has many advantageous properties as regards resistance to fire. It is non-flammable and it has a low thermal conductivity. However, concrete structures, which are not designed for resistance against fire, show significant damage after heating. In particular, the explosive flaking with the consequence of weakening the reinforced concrete cross-section and exposing the steel reinforcement to the temperatures higher than critical temperature of reinforcement. There are only a few possible measures of preventing or mitigating the effects temperature load used. Ways of protection can be divided into two systems: active and passive. Active systems are designed to ensure the greatest possible reduction of temperatures the concrete is exposed to. Passive systems directly resist to high temperatures and fire. Design of composition of concrete with the aim of higher resistance to exposition to high temperatures belongs among the passive systems. A part of the work focuses on summary searches of the problems of concrete and reinforced concrete structures exposed to high temperatures and fire. The goal of the work is defining requirements for cement matrix based composite material and its design ensuring the highest possible resistance to high temperatures or direct fire.
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Durability of repair materials with higher fire resistance for concrete structures
Počekajlo, Václav ; Dohnálek,, Pavel (referee) ; Bydžovský, Jiří (advisor)
This dissertation deals with the study of durability and degradation repair mortars for reinforced concrete structures. In its theoretical part, there are the research findings on the behavior of repair mortars exposed to corrosive environments with different exposure time and selected high temperatures. Processes occurring in repair mortars during their loading at high temperatures or when exposed to chemically aggressive environments are described, We can find recipes designed for cementitious binder based with a specific replacement using slag or fly ash in its practical part. The object of the research was to determine the durability of the proposed repair mortars, and determine their suitability for use on concrete structures, which may be exposed to a synergistic effect of chemically aggressive environments with high temperatures simulating fire.
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The development of fire-resistant repair mortars with fine-grained filler
Záruba, Jiří ; Gross,, Tomáš (referee) ; Bydžovský, Jiří (advisor)
The diploma thesis is focused on fire-resistant repair mortar with fine-grained filler. The aim of this work is the research and development of fine-grained Mortars resistant to high temperatures, which are characteristic at the beginning of the fire. The theoretical knowledge with subsequently realized laboratory verification was used. At-tention was paid to the masses based on the mixed binder comprising cement and blast furnace slag, respectively. high-temperature ash. Cellulose fibres were used as the dis-persed reinforcement. Two kinds of aggregate were assessed - fly ash agloporit and am-phibolite incl. combinations thereof. Laboratory tests were carried out via determination of basic material properties (density, strength, consistency, dimensional changes etc.) after exposure to extreme temperatures. A substantial part of the research was also study of different cooling conditions - slow and fast (water and air). Selected formulations were subjected to temperatures up to 1200 ° C. In the conclusion is selected several recipes that have been found to be optimal for continuing research on the basis of the results and findings.
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Study of the properties of cement composites with polypropylene fiber modified low-temperature plasma
Žižková, Lucie ; Herka, Petr (referee) ; Bodnárová, Lenka (advisor)
Plasma treatment of polypropylene fibers presents a new progressive method, how to increase the utility properties of these fibers. The thesis is focused on verifying the effect of surface treatment of polypropylene fibers in concrete with low-temperature plasma discharge in the normal atmosphere. The paper describes the procedure for treatment of polypropylene fibers with low-temperature plasma and evaluate the impact of this adjustment on the volume changes of cement composites. It should also be emphasized that the thesis is focused on the initial volume changes, ie volume changes in the early stages of solidification and only for your own mixture, which is not considered an external load. Subsequently, the experimental verification of the effect of the addition made commercially available fibers and fibers treated plasma volume changes to a selected physico-mechanical properties of the test compounds.
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The behavior of cementitious composites with fiber reinforcement at high temperatures
Fichtová, Zlata ; Herka, Petr (referee) ; Bodnárová, Lenka (advisor)
This master’s thesis studies the influence of dispersed reinforcement on the behaviour of cement composites at thermal loading. In the theoretical part of the research was performed knowledge of the behaviour of concrete at high temperatures. The paper describes the on-going happening in the individual components of concrete and benefits of using dispersed reinforcement. In the practical part were designed concrete mixtures with different types and quantities of fibers. The object of the research was to determine how different types and amounts of fibers affect the physical - mechanical properties of concrete and their suitability for use in high temperatures.
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Fibre reinforcement with plasma in cement composites
Žižková, Lucie ; Hela,, Rudofl (referee) ; Bodnárová, Lenka (advisor)
The usage of polymer fibres can be increased by the new progressive method of the plasma treatment. This thesis is focused on verification of the influence of the low-temperature treatment on polymer fibres´ surface used in concrete. The treatment of polypropylene fibres in low-temperature plasma is described in the theoretical part. The impact of the treatment on the volume differences of cement composites is also evaluated. The influence of the addition of commercially available fibres and plasma treated fibres on the volume differences of cement composites is also experimentally verified.
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