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Options of determining the frost resistance of concrete in a structure
Jindrová, Barbora ; Vymazal, Tomáš (referee) ; Kocáb, Dalibor (advisor)
The diploma thesis deals with different methods of determining levels of degradation of concrete due to freezing, also considering the options of freeze thaw resistance determination in structure. At first the properties of concrete and possible mechanisms of concrete degradation are described – mainly the effects of freezing water in the inner structure and of the combination of freezing water and de-icing chemicals on the surface. Principle and properties of air-entrained concrete are also mentioned. An overview of the approaches that current standards use to determine the freeze-thaw resistance of concrete is listed, followed by description of the tests that are used on air-entrained concrete specimens in the main part of the thesis. A portion of the test specimens was made in moulds while the rest was obtained from structure (concrete block). The non-destructive tests used are evaluated in several different ways and their results are compared with the destructive tests. Comparison and evaluation of different approaches used to determine the freeze-thaw resistence of concrete are the main outcome of this thesis.
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Technology design watertight concrete
Skřivánek, Michal ; Hubertová,, Michala (referee) ; Hela, Rudolf (advisor)
My work describes technology design of pervious concrete. The theoretical part contains a research about this kind of concrete usually from foreign authors. In general, I focused on the composition of the PC, aggregate grading curve, behaviour of concrete in fresh state, storing and compaction of concrete. A critical part is the aggregate grading curve – it plays the main role in the final level of water permeability. Further, we will go through the real world scenarios where we can use this type of concrete and also through the associated drawbacks. A substantial part of this work is about development of water-permeability test. The practical part shows variety of recipes with a list of measured and observed characteristics (compressive strength, frost resistence and water-permeability). The conclusion includes evaluation of the results and suggestions for future development in this area.
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Possibilities of using recycled aggregates for the production of structural concrete
Hrachovcová, Ludmila ; Brožovský, Jiří (referee) ; Hubáček, Adam (advisor)
The bachelor thesis deals with the study of recycled aggregates and concretes made from them. Nowadays, more and more emphasis is being placed on recycling waste and especially construction and demolition waste. Therefore, we are looking for ways to use recycled aggregates in concrete composites despite heterogeneous parametres of concrete and brick recyclates. The paper summarizes the existing knowledge about recycled aggregates, especially about brick and concrete recyclates, their parameters and possibilities of their use. Furthermore, the thesis deals with brick and concrete recyclate concretes, their parameters and behaviour and their subsequent use in practice.
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Methods of assessing the durability of concrete against frost and chemical deicing salts in the Czech Republic and in Europe
Žíla, František ; Novosad,, Petr (referee) ; Hubáček, Adam (advisor)
The bachelor thesis deals with the methods of assessing the durability of concretes against frost and chemical deicing salts used in the Czech Republic and Europe. The theoretical part of the thesis describes the basic properties of concrete, the classes of environmental influence, the theory of concrete failure by cyclic freezing and thawing, methods for assessing the durability of concrete against freezing and methods for assessing the durability against water and chemical deicing salts, as well as properties affecting the repeatability and reproducibility of tests. The practical part focuses on testing the resistance of concrete to the action of freezing and chemical thawing agents using the methods according to the standards ČSN 73 1322 and ČSN 73 1326 and also on the influence of concrete surface treatment on the process and result of these tests.
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Komplexní metodika pro nedestruktivní a šetrnou semidestruktivní diagnostiku fyzikálně-mechanických vlastností historických pálených zdících prvků
Cikrle, Petr ; Sokolář, Radomír ; Topolář, Luboš ; Pazdera, Libor ; Anton, Ondřej
Uvedená metodika popisuje základní principy a způsob provádění a vyhodnocování zkoušek zdících prvků určených primárně jako náhrada či doplnění stávajícího historického zdiva. Metodika je určena především pro výběr lícových cihel, které musí mít určité specifické vlastnosti, závislé na prostředí jejich aplikace. Tato metodika je aplikovatelná jak na cihlách starých (použitých, získaných ze zbouraných konstrukcí), tak na nových vyrobených v cihelně, ať už se jedná o běžnou produkci nebo speciálně vyráběné repliky historických cihel. Metodika využívá rozsáhlý soubor zkušebních metod, které však nemusí být vždy v celé šíři využity v závislosti na konkrétních požadavcích na zdící prvky. Novost postupu metodiky spočívá v komplexním zapojení zcela nedestruktivních elektroakustických metod – metody impact-echo, metody rezonanční a metody ultrazvukové impulzové, které posouvají tradiční třídění na výrazně vyšší úroveň. Díky zapojení nedestruktivních zkoušek, jejichž provedení je relativně jednoduché a časově nenáročné, přičemž výsledky jsou u většiny z nich okamžitě viditelné v reálném čase, umožňuje tato metodika provést kvalifikovaný předvýběr souborů cihel vhodných pro náhradu historického zdiva a následně u vybraných souborů provést jejich efektivní třídění a vzorkování, včetně výběru zkušebních vzorků pro ověření fyzikálně-mechanických vlastností cihel tradičními laboratorními metodami. Díky řadě provedených srovnávacích zkoušek (nedestruktivní × destruktivní) na souborech různých cihel z různých období je dokonce možné částečně predikovat trvanlivost (mrazuvzdornost) cihel a provést jejich základní roztřídění do skupin: 1) vhodné pro použití, 2) diskutabilní, 3) zcela nevhodné. Uvedené nedestruktivní zkoušky však mají značný význam i pro posouzení nových cihel, např. pro odhalení textury, která je jednou z hlavních příčin snížené mrazuvzdornosti cihel. Rovněž lze pomocí těchto metod provést třídění cihel přímo ve výrobně (zejména v případě starších typů pecí, kde je poměrně velká variabilita vypálených cihel). V neposlední řadě lze odhalit případnou dodávku špatných (nekvalitních) cihel a zabránit jejich zabudování do stavby. Metodika byla ověřena nejen prostřednictvím velkého množství laboratorních zkoušek cihel různého stáří (cihly gotické, renesanční, barokní, novodobé z 19. století a současné), ale rovněž přímo in situ v rámci rekonstrukce unikátní technické památky – barokního mostu Portz Insel u Mikulova, kde byla přímo aplikována pro výběr náhradních cihel určených pro obnovu chybějících částí mostu (původních barokních, nově vyráběných i použitých ze zbouraných staveb).
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The comparison of testing methods using for determining the frost resistance of concrete
Kněbort, David ; Vymazal, Tomáš (referee) ; Kocáb, Dalibor (advisor)
The diploma thesis deals with the possibilities of evaluating the degradation of mechanical resistance of non-air-entrained concrete in the structure by frost cycles. The first part is focused on concrete, its resistance and test methods. This is followed by the definition of frost resistance, the effects of freeze-thaw on concrete at all stages of its service life and the possibilities of determining freeze-thaw resistance according to current standards. It describes in more detail selected test methods for determining frost resistance. In the practical part, it focuses on the determination of degradation resistance of test specimens made in molds and taken from the structure using reference and non-reference methods. In conclusion, it compares the different test methods and their suitability for the determination of freeze-thaw resistance.
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Historický vývoj a možnosti pěstování fíkovníku smokvoně (Ficus carica L.) v podmínkách ČR.
Malárová, Michaela
This bachelor thesis is focused on the history of growing common fig Ficus carica L. in our country, characterizes fig tree greenhouses with the best known examples, deals with the issue of fig tree adaptability in relation to growth physiology, the course of dormancy and frost resistence. The thesis defines the sum of chilling hours and compares them with other fruit species. After evaluating the available information, it can be stated that due to its ability to adapt to climatic conditions, the fig tree can be grown in outdoor cultures all year round in the warmest regions of the Czech Republic.
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Možnosti pěstování rakytníku řešetlákového v podmínkách ČR
Hynek, Petr
This thesis deals with the evaluation of the available books and possibilities of the growing of sea buckthorn (Hippophaë rhamnoides L.) in the Czech Republic. Physical and chemical values which are necessary for planting sea buckthorn in the area of Lednice were measured and specified. The female plants of the species of ´Buchlovsky 1´, ´Hergo´, ´Leikora´, ´Vitamínová´, and the male plant of ´Buchlovsky 2´, ´Pollmix´ and ´Ruský´ were studied and evaluated. As for the products made of sea buckthorn, speads and juices with various amount of sugar, baked tea and sweetened sea buckthorn powder were evaluated from the sensory point of view. The issues of the growing and processing of s ea buckthorn were discussed with the producers of planting stock, commercial croppers and manufacturers within the whole Czech Republic. Sea buckthorn is not widespead and commercial area for growing does not meet the needs of the manufacturers. If all biotic and abiotic factors are taken into account, the growing of sea buckthorn is recommended in the Czech Republic.
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Testing of bricks intended for the repair of monuments
Lezová, Lívia ; Anton, Ondřej (referee) ; Cikrle, Petr (advisor)
The bachelor thesis is focused on methods of testing bricks, which will use to classify historic bricks into groups on usable, usable in extreme conditions, usable in limited extent and unusable for restoration of monuments or for construct new constructions. In the theoretical part, there is describe of historical development of solid fired bricks in Central Europe and an overview of methods for testing bricks, including a description of an accomplishments and their evaluation. In the practical part, there are methods applied to three visually different sets of bricks taken from 19th century construction.
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Options of determining the frost resistance of concrete in a structure
Jindrová, Barbora ; Vymazal, Tomáš (referee) ; Kocáb, Dalibor (advisor)
The diploma thesis deals with different methods of determining levels of degradation of concrete due to freezing, also considering the options of freeze thaw resistance determination in structure. At first the properties of concrete and possible mechanisms of concrete degradation are described – mainly the effects of freezing water in the inner structure and of the combination of freezing water and de-icing chemicals on the surface. Principle and properties of air-entrained concrete are also mentioned. An overview of the approaches that current standards use to determine the freeze-thaw resistance of concrete is listed, followed by description of the tests that are used on air-entrained concrete specimens in the main part of the thesis. A portion of the test specimens was made in moulds while the rest was obtained from structure (concrete block). The non-destructive tests used are evaluated in several different ways and their results are compared with the destructive tests. Comparison and evaluation of different approaches used to determine the freeze-thaw resistence of concrete are the main outcome of this thesis.
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