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Studying the effect of the application of inorganic nanofibers in high strength concretes
Sedláček, Daniel ; Hela, Rudolf (referee) ; Bodnárová, Lenka (advisor)
This thesis summarizes the current knowledge of reinforcement of concrete with nanofibers and conducted research on the issue of the use of inorganic nanofibers in ultrahighperformance concrete. Up to now, most researches focuses on the reinforcement using carbon nanotubes and nanofibers and inorganic nanofibers remained in the background of interest. Due to their different chemical properties, is not only a question of their influence on the microstructure and mechanical properties of concrete, but also the preparation of nanofiber suspension which is not explored such as in the case of carbon nanotubes and nanofibres.
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Studying the behavior of concrete at high temperatures
Čonka, Ladislav ; Sitek,, Libor (referee) ; Bodnárová, Lenka (advisor)
The thesis is focused on the current issues of concrete resistance to high temperatures. The theoretical part has been processed the changes taking place in the individual components of concrete and changes affecting the physical - mechanical properties of concrete and color-changing effects manifesting high. In the experimental part of the load was, carried concrete test samples to a temperature of 400 ° C, 600 ° C and 800 ° C. After the thermal load, has been on test samples tested changes in physico - mechanical properties, especially concrete compressive strength, water absorption but also a visual assessment of the concrete surface
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Study possibilities of nanotechnology in cement composites
Kardošová, Romana ; Bodnárová, Lenka (referee) ; Hela, Rudolf (advisor)
The aim of this paper is to summarize and assess the possibility of using nanoparticles as additives in concrete. These particles have the ability to improve the mechanical and physical properties of cement composites or even gave them brand new ones. Industrial use is hampered by effective incorporation of nanoparticles into the matrix, the health and environmental risks and, last but not least, the financial costs. The experimental part of the thesis deals with the dispersing nanosilica and nanometakaolin particles in aqueous solution and their subsequent integration into the structure of cement mortar.
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Impact of input parameters on the quality of mixing dispersion of nanoparticles
Cederová, Kristýna ; Hela, Rudolf (referee) ; Bodnárová, Lenka (advisor)
The bachelor thesis deals with nanoparticles. It examines the process of dispersion of nanoparticles in particular. Nanoparticles have the ability to improve some physical properties of cement composite materials. One, but important obstacle for correct application of nanoparticles is its dispersion. The experimental part of the thesis is dedicated to the dispersion of nanoparticles. Properties of cement composites were set in a time of 7 and 28 days. Nanoparticles were examined under transmission electron microscope.
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The study of the influence of the composition of the lightweight fiber concrete physical and mechanical properties
Šindelek, David ; Bodnárová, Lenka (referee) ; Hela, Rudolf (advisor)
This bachelor thesis deals with a study of light construction concrete with an addition of steel fibre which monitors its impact of the physical mechanical properties. The work is divided into two parts, theoretical and practical. The theoretical part is focused on characteristics and a design of light concrete within the class 35MPa and over with the density within the class of D1,8. Furthermore, it focuses on the increase of toughness of cementitious composites with the form of application of steel fibre in different doses and lengths. In the practical part, formulas of two strength classes 35/38 D 1,8 and 45/50 D1,8 were designed with the help of the steel fibre Krampeharex in doses of 25 and30 kg/m3, and where there were both its impact of the working diagram as well as the compressive strength monitored for the duration of twenty-eight days
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The influence of parameters on the quality of the dispersion medium mixed nanoparticles
Kutová, Lenka ; Hela, Rudolf (referee) ; Bodnárová, Lenka (advisor)
The thesis deals with monitoring the characteristics of cement composite using nanoparticles. The theoretical part describes nanoparticles production, their characteristics and influence on cement composites, both in fresh and hardened state. In the practical part of the thesis physically-mechanical characteristics of cement composites with nanoparticles are determined. The microstructure of the composites was monitored on a scanning electron microscope for 1, 3, 7 and 28 days of maturing. And finally mechanical characteristics of the composite and the reference samples without nanoparticles were compared.
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Durability of alkali-activated materials
Zourek, Milan ; Hela, Rudolf (referee) ; Bodnárová, Lenka (advisor)
This bachelor’s thesis deals with durability of alkali-activated materials and the use of them in aggressive surroundings, especially in sewer systems. The first half of the theoretical part summarizes requirements for concrete sewer pipes. The most common linings and coatings used in concrete sewer systems are mentioned. The second half of the theoretical part deals with alkali-activated materials, raw materials used for their preparation and their durability. Concretely sulfate attack resistance, chloride attack resistance, acid attack resistance, abrasion, porosity, freeze-thaw resistance, thin layer applications and cracking tendency. In the experimental part of this bachelor’s thesis there were proposed five types of alkali-activated materials application in the aggressive environment of sewer systems. Density and consumption of alkali-activated material by thin layer application was determined as fresh properties. Material was monitored during its solidifying and hardening, especially for crack formation. As hardened properties density, flexural strength, compressive strength, adhesion of thin layer to concrete, thickness of thin layer, freeze-thaw resistance, resistance of surface to water and defrosting chemicals were determined.
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Portland cement with limestone and Blended Portland cements - properties, possibilities of use.
Matyk, Tomáš ; Hela,, Rudolf (referee) ; Bodnárová, Lenka (advisor)
The current cement production is environmentally and economically challenging, that’s why the global trend is reducing the amount of portland clinker produced and it’s replacement by minerals without clinker. Portland blended cements are environmentally friendly and economical option. Accept of these cements into practice is necessary to summarize the properties and behavior of concrete made from these cements. The work focuses on the behavior of concrete with portland limestone cements and portland blended cements in aggressive environments.
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Design of mixing ratio of two quarried aggregates fraction 0/4 mm for readymix concrete
Jastrzembská, Alena ; Dorazilová, Irena (referee) ; Bodnárová, Lenka (advisor)
This diploma thesis describes with mixing ratio of two kinds of small quarried aggregate for the production of ready mix concrete. The theoretical part summarizes the requirements of Czech technical standards to individual components of concrete, particularly the requirements for fine aggregates. In the practical part were designed the recipes for three classes of concrete and was done checking the properties of concrete in fresh and hardened state. Based on the results were determined the optimal mixing ratio of fine aggregate from location Smiřice and Lípa.
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Study of the effect of the application of cellulose fibers in cementitious composites
Dvořák, Richard ; Herka, Petr (referee) ; Bodnárová, Lenka (advisor)
This diploma thesis is focused on composition and processing of cellulose fibers and their usage in cementitious composites. It describes key attributes of cellulose fibers, which has to be acquired for effective use in cement composites. There are stated effects of cellulose fibers on concrete properties, such as workability, physical and mechanic attributes and freeze-thaw resistance. In experimental part is designed a mixture with portion of cellulose fibers. There has been performed various tests to define the effect of cellulose fibers. There was designed experiment to determine its alkali resistance for fibers itself, and possible changes in microstructure of fibers were analyzed by optic and electron scanning microscope.
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