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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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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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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 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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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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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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The possibility of using recycled concrete for the production of structural concrete
Pijáčková, Erika ; Křížová, Klára (referee) ; Hela, Rudolf (advisor)
The bachelor's thesis deals with the topic of recycled concrete aggregate and its use in the field of structural concrete. The aim of the work was to describe the possibility of complete or partial replacement of natural aggregates with recycled concrete aggregates for concretes of strength classes C16/20 to C30/37. The theoretical part is composed of findings from both domestic and foreign research and legislation, which were used to evaluate the possibility of more frequent use of recycled concrete aggregates in civil engineering in the Czech Republic. The experimental part consists of the design of concrete recipes with natural and concrete recycled aggregates and their economic evaluation.
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