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Study of fibres behaviour in cement composite
Nešporová, Tereza ; Křížová, Klára (referee) ; Sedlmajer, Martin (advisor)
Bachelor thesis is focused on behavior of fibers on selected properties of fine–grained cementitious composite in fresh and hardened state. The emphasis is on usage of enviromentaly friendly fibers, specifically fibers obtained from recycled materials. Different fibres in cement composites are compared in terms of geometry and material base. The findings at the theoretical level are summarised, including information from scientific studies. Practical determination of selected properties on fresh composite such as consistency and shrinkage of the material is covered. Mechanical properties such as flexural tensile strength and compressive strength are also determined. The water permeability is also investigated.
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Use of organic fibers in fine-grained cement composites and their influence on the monitored properties
Mazán, Tomáš ; Ondráček, Michal (referee) ; Křížová, Klára (advisor)
The diploma thesis describes the possibilities of using organic fibres to improve the properties of cement composites at high temperatures. The theoretical part of the thesis deals with the behaviour of the different components of concrete and concretes in fire. A substantial part is devoted to the types of fibres, the method of dosage and the effect of their use on selected parameters. The practical part of the thesis is based on the developed methodology. On the basis of the results obtained, a summary of the behaviour and transformations of different types of organic fibres when exposed to temperatures from 20 to 800 °C was compiled. Furthermore, the observed parameters and the effect of the fibres, especially on the strength of the composite loaded at high temperature, are evaluated. The final of thesis concludes with recommendations for fibre dosage and the suitability of using recycled fibres.
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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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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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