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Possibilities of using light artificial aggregate based on sintered high-temperature fly ash in heat-resistant concrete structures
Mazán, Tomáš ; Sedlmajer, Martin (referee) ; Křížová, Klára (advisor)
The final thesis describes contemporary knowledge of research and development in the area of the heat-resistant concrete constructions with using porous aggregate from flying ash. The theoretical part introduces the production and the agloporit aggregate basic features. The principles of using in the incoming materials of light weight concrete are presented next. The thermal loading with influence at concrete constructions and the other individual materials is also mentioned in the final thesis. The experimental part of the thesis deals with the impact of lightweight aggregate quantity on the high temperature resistance. Conclusion pays attention to the obtained results evaluation and to the composition an optimal formula LWAC, which could be able to resist short-term thermal loading.
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Influence of the type of dispersed reinforcement on selected properties of concrete
Gajdušková, Patricie ; Křížová, Klára (referee) ; Sedlmajer, Martin (advisor)
This thesis is focused on the usage of fibers in concrete. The fibers are dispersed reinforcement which may have different behaviour based on the material characteristics or the geometric shape of the fibers. Due to this, we may predict the appropriate application of fibers and possibly improve mechanical properties of concrete. At the same time, the influence of used fibers on the behaviour of the concrete when exposed to high temperatures, thus the fire resistance of material, is observed. The purpose of this thesis is to compare the properties of the individual fiber types in concrete, which are suitable for specific application of fibre reinforced concrete.
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Influence of high temperatures on concrete properties
Klobása, Jan ; Křížová, Klára (referee) ; Sedlmajer, Martin (advisor)
The aim of this bachelor thesis is to study the problem of the behavior of concrete under high temperatures. The theoretical part of the work summarizes the knowledge about the changes that take place in concrete when it is exposed to a high thermal load that simulates the effects of fire. It also summarizes the effect of high temperatures on the behavior of the individual components that make up concrete. Emphasis is placed on describing the possibilities of eliminating concrete damage at high temperatures. Furthermore, the principles of changes and events due to high temperatures simulating the effect of fire are described. The experimental part summarizes the knowledge related to the composition of concrete, the use of different types of fibers, and other measures in loading concrete at high temperatures. Steps influencing the negative impact on the properties and resistance of concrete to high temperatures are also described. Based on the summarized findings, conclusions are formulated.
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Influence of environmental conditions on the modulus of elasticity of concrete
Peřina, Tomáš ; Novosad, Petr (referee) ; Křížová, Klára (advisor)
Increasingly, the modulus of elasticity of concrete is at the forefront of interest. In the past, it has been neglected to some reason and not taken into due consideration. The theoretical part of the bachelor thesis is to study of factors influencing the static modulus of elasticity in compression. The practical part is focused on monitoring the modulus of elasticity of concrete, based on the different type of the environment stored test specimens. Concrete will be stored outdoor in the water and in the laboratory environment conditions. Designed concrete mixes will be primarily different with the used of type of admixtures but also with type of cement. The result values will be compared on the dependence of environmental conditions of the test specimens.
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Current development of UHPC concrete and verification of selected properties
Panenková, Monika ; Sedlmajer, Martin (referee) ; Křížová, Klára (advisor)
This bachelor thesis deals with current developments and research in the field of ultra high performance concrete – UHPC. Theoretical part of this work is focused on the composition and properties of UHPC compared to normal strength concretes. It describes design principles, constructions in the world and also in the Czech Republic and other use of this material. Experimental part describes the design of UHPC, manufacture of test specimens and testing for certain physical and mechanical properties such as compressive strength, tensile strength, bending strength, water impermeability, frost resistance, resistance to chemical de-icing substances and abrasiveness of the material.
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Possibilities of using lightweight aggregate of the foam glass bonded with cement
Jahn, Jeroným ; Křížová, Klára (referee) ; Sedlmajer, Martin (advisor)
In the theoretical part of bachelor thesis are findings about use of lightweight aggregate from foam glass. Part of this work is a description of production , raw materials for production , and especially the properties of aggregates. The work deals possibilities of interconnection and the use of foam glass aggregates in building industy . There is describe a risk of alkali-silica reactions in combination with cement. In the practical part are verified application possibilities and properties of cement composite with lightweight aggregate foam glass .
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Optimizing the composition of micro concrete admixtures.
Juříková, Denisa ; Křížová, Klára (referee) ; Hela, Rudolf (advisor)
The aim of this paper is to summarize knowledges related to the use of fine-grained admixtures in cement composites. By utilizing of these admixtures it is possible to achieve extreme properties, especially high strenght and durability of concrete. These properties can be achieved by optimizing the density of the binder and filler in range of 0 to 0,25 mm. Therefore, large part of thesis is focused on admixtures and its effect on concrete. The experimental part of the thesis deals with optimization od selected admixtures in combination with cement to achieve the minimum of the voids and their compressive strenght were determined at 1, 3, 7, 28 and 60 days.
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Study of the dependence of concrete composition on the values of elasticity modules
Křížová, Klára ; Kolář,, Karel (referee) ; Adámek, Jiří (referee) ; Ďurica,, Tibor (referee) ; Hela, Rudolf (advisor)
The modulus of elasticity is one of the basic characteristics of concrete defining elastic deformation of concrete and it plays a significant role in the static design of structures. Due to current trends in concrete technology, offering a wide variability in the proposals of the composition of concrete, there are changes not only in strength characteristics but also in the modulus of elasticity of concrete. The aim of this doctoral thesis is to study the dependence of different compositions on modulus of elasticity of concrete. Design of concrete composition is prepared with respect to the use of different types of cement, mineral admixtures, types and fractions of aggregates. The work is mainly focused on the determination of static modulus of elasticity in compression with the addition of dynamic modules. In the first phase determined modulus of elasticity are compared with tabulated values according to Eurocode 2, which are derived for the specific strength class of concrete. Part of this work is the compilation of the main technological aspects of concrete which can favorably affect the modulus of elasticity.
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Study of the influence of feedstock composition and the values of the modulus of elasticity of concrete
Šafrata, Pavel ; Křížová, Klára (referee) ; Hela, Rudolf (advisor)
Modulus of elasticity is significantly reflected feature of concrete, besides the compressive strength in static design nowadays. Low modulus of elasticity can cause unacceptable deflections for subtle skeletal structures. It is at least irresposible to count with empirical formulas since there is a wide range of materials and additives in production of concrete. The aim of this thesis is to study the influence of large fraction aggregate on static and dynamic modulus of elasticity of concrete and recommendation for appropriate measures to produce concrete with high modulus of elasticity. The experimental part is further following up the influence of air content in concrete on the modulus of elasticity.
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