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Study of rheological properties of concrete with the addition of low-temperature plasma treated polymer fibers
Gromeš, Vít ; Herka, Petr (referee) ; Bodnárová, Lenka (advisor)
Polypropylene fibers are used in concrete mixtures to avoid early cracks during shrinkage. Low thickness of each fiber and low density are reasons, why these fibers are effective in small dosage. Their disadvantages are smooth surface and hydrophobic character of polypropylene, thus it is necessary to improve their surface for better spread during mixing and to reach needed adhesion between fibers and cement paste. In present time are using chemical solutions applied on surface of the fibers to provide better water absorption, but the trend is reducing of using chemicals in industry and this situation demands new technology. There is possible solution, polypropylene fibers treated by low-temperature plasma. This method was developer by cooperation Masaryk University in Brno with company KrampeHarex and Brno Universiry of Technology. The goal of this thesis is to bring comparison, of influence on rheology properties of fresh concrete, between admixed the fibers with applied chemical layer and low-temperature plasma treated polypropylene fibers.
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Effect of addition of polypropylene fibers on the properties of concrete
Svozil, Jaroslav ; Zábojník, Martin (referee) ; Bodnárová, Lenka (advisor)
The thesis evaluates the influence of the addition of polypropylene fibers on the properties of concrete. One of the major elements is to compare different finishes polypropylene fibers without static functions, including low temperature plasma treatment plasma. The main work is to test the knowledge of the properties of fresh concrete with these fibers, as well as testing volume changes and finally testing these concretes on physical and mechanical properties
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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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Studying the behavior of concrete at high temperatures
Tillová, Jana ; Herka, Petr (referee) ; Bodnárová, Lenka (advisor)
This master‘s thesis is focused on the study of the behavior of cement concrete at high temperatures with a focus on monitoring the impact of aggregate and cement type. This work describes the processes in aggregates and cement matrix at high temperatures. The theoretical part describes the selestion of a suitable aggregate and cement for the surroundings with potential exposure to high temperatures. In the experimental part is given design of composition of a concrete with two types of aggregates and four cements. It has been suggested 8 recipes. Changes were observed densities, compressive strength and tensile strength in bending, calculate the velocity of propagation of waves with ultrasonic pulsed method. Also evaluated the appearance of the surface samples after thermal load – cracks on the surface and measure the maximum crack width.
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Properties of concrete with the addition of plasma modified polypropylene fibers
Vorel, Pavel ; Herka, Petr (referee) ; Bodnárová, Lenka (advisor)
Master‘s thesis focuses on concrete combined with polypropylen fibres produced commercially, fibres without surface modifications and fibres modificated by plasma. Most important topic of the thesis is experimental verification of influence of plasma modificated fibres on attributes of fresh concrete and physical-mechanical attributes of solidified concrete. Based on the results of the tests perfomed on examin units compares results and anylyses applicability of different fibre surface modifications.
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The concrete with a higher resistance to high temperatures
Mikulinec, David ; Hela,, Rudolf (referee) ; Bodnárová, Lenka (advisor)
The result of this master’s thesis is acquaintance with the issues of cement concrete resistance to high temperatures. This work describes the processes ongoing in the structure of concrete at extreme thermal loads and analysis of effects of high temperatures on the individual components of reinforced concrete structures is given, then influence of high temperatures and fire on the aggregates, matrix, reinforcement steel and the resulting changes in their properties. In the experimental part is given design of composition of concrete with a higher resistance to high temperatures and subsequent verification of the physico-mechanical properties of sample of concrete after exposure to temperatures at intervals of 200 ° C, 400 ° C, 600 ° C and 900 ° C. In individual recipes were observed changes of volume weight, changes of compressive strength and tensile strength flexural , tensile strength of surface layers and the occurrence of cracks and then were compared the results of thermally loaded and unloaded samples. The benefit in this issue is to evaluate the surface appearance of samples after heat load - study of area of crack and measurement of their width - was used according to the methodology's authors Xing, Hebert, Noumowe a Ledesert given in Cement and Concrete Research. This methodology allows to quantify changes of surface, after temperature load.
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Study of dispersion of carbon nanotubes in cement composites
Michnová, Kamila ; Hela, Rudolf (referee) ; Bodnárová, Lenka (advisor)
Carbon nanotubes have the ability to improve the mechanical and physical properties of cement composites. However, their introduction into industrial utilization is hampered by several obstacles. It primarily involves the effective incorporation into the cement matrix, health and ecological risks. The experimental part of the work deals with the dispersing carbon nanotubes in aqueous solution and their subsequent integration into the structure of the cement matrix.
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Studying the behavior of cement concrete at high temperatures
Sovová, Kateřina ; Sitek,, Libor (referee) ; Bodnárová, Lenka (advisor)
Bachelor thesis is divided in two parts, theoretical and practical. In theoretical part are listed behaviour of cementious concrete at high temperatures and knowledge from particular construction, that was damaged by fire. There is given procedure of diagnostics for collected speciments of fire-damaged construction. In named analysis belong the carbonation depth through phenolphthalein solution and test of compressive strenght according DIN EN 13791 2008-05. In this study are demostrated results of tests, that were made on materials exposed to high temperatures. Result of constructions analysis is evaluation of economical reapairing works for safety. Practical part deals with measuring thermal conductivity at standard temperature and at high temperatures.
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Studying the properties of high strength concrete using micro and nano admixtures
Gabko, Miroslav ; Bodnárová, Lenka (referee) ; Hela, Rudolf (advisor)
The objective of this bachelor thesis is to examine the properties of high strength concretes with the main focus on application of mikro or nano admixtures. In theoretical part their production, the properties and the influence on fresh and hardened properties of cement composites are described. In addition, it explores the influence of plasticizer type, some properties of aggregate and cement types. The practical part focuses on testing cement mortars in which fine cements were added. The compressive and flexural strengths were examined after 7 and 28 days of curing, moreover, rheological properties and heat hydration of cements were also observed. Furthermore, the influence of high speed mixing on cement mortars properties was studied.
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