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Use of acoustic methods for assessing the influence of the composition of cement composites on the course of degradation caused by high temperature
Dvořák, Richard ; Medveď,, Igor (referee) ; Bílek,, Vlastimil (referee) ; Bodnárová, Lenka (referee) ; Chobola, Zdeněk (advisor)
The aim of this work is to optimize the acoustic nondestructive method (NDT) Impact-Echo (IE) as a complementary diagnostic tool for the assessment of concrete structures exposed to high temperatures. Commonly used diagnostic procedures for concrete structures affected by fire are most often limited to in-situ core drilling and subsequent testing of the drilled holes by destructive testing. The Impact-Echo method allows non-destructive testing of variously degraded test specimens and concrete structures, but its use for the assessment of temperature-degraded cementitious composites is hardly ever used in practice. Many studies suggest that Impact-Echo is one of the most suitable non-destructive methods for assessing the rate of degradation by elevated temperature. The dissertation work consists of three main stages, where the first stage is devoted to the production of test specimens of different mixtures and their subsequent degradation by elevated temperature and testing by the IE method and by reference destructive and non-destructive methods. The second stage consists of manufacturing a reinforced concrete element with built-in thermocouples and its subsequent inhomogeneous degradation by a local source of elevated temperature. The controlled degraded element thus prepared contains all grades of thermally degraded concrete tested in the first stage. Subsequent testing consists of verification of standard procedures in the field of acoustic NDT with simultaneous use of experimental modal analysis. In the third stage, the objective is to interpret the measured data from both previous parts, to verify whether within the closed element temperature-degraded areas can be distinguished from one another, or the degree of thermal degradation of concrete. Based on these results, the optimal testing procedure was determined and the basic assumptions for the creation of degrees of damage of the concrete by increased temperature were determined.
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Study of properties of bent FRP reinforcement
Lipoldová, Marie ; Prokeš,, Jan (referee) ; Bodnárová, Lenka (advisor)
The diploma thesis deals with the study of bent FRP reinforcements with the main focus on the methods of production of bent FRP reinforcement, examples of their application in structures. The work also mentions the effects of aggressive environments on the durability of FRP. In the practical part, a search of the possibilities of testing the properties of bent FRP reinforcement. Subsequently, an experiment is designed and performed to monitor changes in the properties of straight and bent FRP reinforcement exposed to the alkaline environment and water at 20 °C and 40 °C. Finally, the evaluation of changes in mechanical properties and observation of reinforcements using optical and scanning electron microscopy is performed.
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Study of the effect of selected types of aditives on the properties of cement composites
Kavka, Lukáš ; Ťažký, Tomáš (referee) ; Bodnárová, Lenka (advisor)
The diploma thesis describes admixtures for concrete. It deals with the influence of admixtures on the properties of cement composites in the fresh and hardened state. The theoretical part described the individual components of concrete, where the main attention was focused to inert admixtures and their effect on mechanical properties, shrinkage, resistance of cement composites to aggressive medium. Furthermore, the effect of admixtures on concretes with recycled aggregates was described. In the first stage of the practical part, cement mortars with 25, 35 and 50% replacement of cement admixtures were created. In the second stage, concretes with admixtures and a minimum strength class of C30/37 and C50/60 were created. Finely ground granulated slag, micronized limestone and granite stone dust were used as admixtures in mortars and concretes. The change of properties in the fresh and hardened state was observed on cement composites.
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Study of properties of cement composites with addition of polymer fibers
Dokoupil, Tomáš ; Hela, Rudolf (referee) ; Bodnárová, Lenka (advisor)
The bachelor thesis deals with the use of polymer fibers in cement matrix. It describes the distribution and production of the most commonly used polymer fibers as well as the requirements for their properties. A comparison of the properties of different types of polymer fibers is given. The work presents the individual components of the fiber concrete matrix, its production, testing of fresh and hardened fiber concrete and specific examples of its use in practice. Using professional research, the influence of PP, PE and PVA fibers on the properties of fresh and hardened concrete is described in detail. New trends in the use of polymer fibers are also presented. At the end of the work, a procedure of experimental verification of the properties of fiber-reinforced concrete in comparison with a reference sample of plain concrete is proposed.
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FRP for concrete reinforcement
Blahová, Aneta ; Vaněrek, Jan (referee) ; Bodnárová, Lenka (advisor)
The bachelor thesis deals with composite polymer FRP reinforcement. It descibes the method of manufacturing FRP reinforcements, which are their properties and what materials are used by manufacturers. Lists FRP reinforcement application in various structures. Also mentions the durability of FRP reinforcement in an aggressive environment and the cohesiveness of FRP reinforcement with concrete. The conclusion of the work is a proposal for experimental testing of a bond between FRP reinforcement and concrete.
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Development of abrasion-resistant concrete and testing methods
Procházka, David ; Bodnárová, Lenka (referee) ; Hela, Rudolf (advisor)
This diploma thesis deals with concrete abrasion resistance against abrasion. The constructions of transport and water management structures are most stressed by the action of abrasion by means of travel of vehicles and flowing water. Abrasion reduces the durability of the structures. The prerequisites for achieving the best possible abrasion resistance are examined. Furthermore, test methods that are currently used worldwide. The experimental part deals with the influence of individual types of aggregates amphibolite (Želešice), fecal gravel sand (Žabčice) and basalt (Bílčice) on abrasion resistance. Furthermore, the dependence between the strength of the concrete and the hardness of the surface for abrasion resistance. Abrasion resistance testing was determined by concrete abrasion, abrasion resistance by the Böhm method and by water jet.
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Cement Composite for 3D Printing Technology
Lipoldová, Marie ; Hela, Rudolf (referee) ; Bodnárová, Lenka (advisor)
3D printing technology represents a fast-growing industry within many industrial sectors. This bachelor thesis is focused on possibilities of using 3D printing technology in building industry. In the theoretical part there are stated typical technologies and realizations of 3D printing in the field of construction. The thesis also includes a research which is essential for the determination of requirements for cement composites for 3D printing technologies including tests for verification of their properties. The experimental part of the bachelor thesis is focused on testing of various recipes of cementitious composites, especially on the properties of both fresh and hardened composites. Two batches were tested for the suitability of utilisation of waste PET particles.
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The effect of appication of fine organic fibers to cement composites
Kavka, Lukáš ; Hela, Rudolf (referee) ; Bodnárová, Lenka (advisor)
This bachelor thesis describes the effect of using fine organic fibers in cement composites. In the theoretical part of bachelor thesis a composite material was defined and his individual components were described. Then was created a research of information about organic fibers focused on natural fibers. The basic parameters of cellulosic fibers and polypropylene fibers, the effect on the properties of cement composites and their application in practice were described. In the practical part there were created a reference concrete and 3 types of concrete with the addition of various types of organic fibers. The influence of fiber addition on the properties of fresh and hardened concrete were investigated. Another task of practical part was monitored the resistance of cellulose fibers in acidic and alkaline media in which the tested fibers were deposited. The development of pH solutions was examined over time.
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Verification of properties of concretes with nanoparticles
Pacltová, Klára ; Hela, Rudolf (referee) ; Bodnárová, Lenka (advisor)
This diploma thesis deals with the influence of addition of carbon nanoparticles on cement composites. The theoretical part of the diploma thesis is focused on the research of information about carbon nanoparticles, more precisely about carbon nanotubes and graphene oxide. There are summarized methods of dispersing carbon nanotubes and their effects on cement composites. The practical part follows the theoretical part of the research. In the first phase, the correct technique of graphene oxide dispersion was verified. Subsequently, the effects of graphene oxide on the mechanical properties of cement mortars were verified. In the final phase of the diploma thesis, the knowledge gained from the previous part was verified on concrete samples.
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