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Development of Self-leveling Screed Based on the Ternary Binder System
Běťák, Rostislav ; Vojtek, Miroslav (referee) ; Gazdič, Dominik (advisor)
The thesis deals with the development of self-leveling cement screed with compensated shrinkage. It is a ternary binder system with the majority of portland cement, that in the beginning of setting and hardening form an expandable folder ettringite. At first there was a background research of volume changes of hydrating cement composites and methods for measuring these changes. Various sort of expansion additives were also introduced, the main emphasis was on concepts of calculated formation of ettringite, which are typical for self-leveling underlayment. Background research included the issues of formation of ettringite, influences on it’s nucleation and it’s stability. The practical development of the screed began by measuring volume changes of different pastes on a ternary composition. Selected formulations suitable for use are verified together with additives to semi-application tests. After the final configuration of the screed mixture, there was a test in real application of an representative area. Individual formulations were tested in terms of long-term stability of ettringite in dry and moist environments.
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Production of threads with taps
Chludil, Petr ; Sliwková, Petra (referee) ; Píška, Miroslav (advisor)
This thesis deals with the study of production process of threads by screw-taps from the very description of the individual threads through all the available methods of the threads production, thread control function, up to the actual taps, materials, coatings and their distribution. In the experimental part the thesis deals with the question whether it is possible to find an alternative to the standard production of threads using cutting by taps. This alternative seems to be the use of forming taps. The experiment took place under constant cutting conditions and consisted of two parts, one of them was the production of threads into the pre-drilled through holes and the second one was the production of threads into the pre-drilled impassable holes. The result of the experiment was finding the course of the cutting moment depending on the time and the amount of wear of the examined kinds of taps when all the measured values had to be statistically processed and conclusions were then evaluated.
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Geopolymers based on fly ashes and brick body
Řezník, Bohuslav ; Lang,, Karel (referee) ; Příhoda,, Jiří (referee) ; Žižková, Nikol (referee) ; Rovnaníková, Pavla (advisor)
In line with the current focus on utilizing side products of various production processes, this dissertation thesis analyzes the process of alkali activation of particular side products: fly ash and brick fragments. This activation produces geopolymeric materials widely used in civil engineering. The thesis aims to optimize the geopolymerization process so that the resulting geopolymer is both ecologically and economically viable. To that end, the thesis studies the course of geopolymeric reaction between the alkali activator and fly ash from: (i) the Chvaletice power plant, (ii) the Dětmarovice power plant, and (iii) biomass combustion, as well as (iv) fluid fly ash from the Hodonín power plant. All experiments of geopolymeric reaction have focused on the factors influencing the synthesis of geopolymers—that is: composition of the alkali activator, the ratio of alumino-silicate to the activator, and the impact of temperature on structure of the synthesized geopolymer. Further, the thesis analyzed the synthesized polymer’s microstructure, phase composition, resistance against corrosive conditions, and compressive strength, as well as mechanical-fracture properties of selected fly-ash geopolymers. The thesis finds that the most suitable for geopolymeric synthesis appears to be the fly ash from the Chvaletice power plant in which case the obtained geopolymers showed best properties in the studied areas. The fly ash from the Dětmarovice power plant, biomass fly ash, and fluid fly ash have failed to reach acceptable properties. Separately, the thesis studies the geopolymerization of brick body that could be suitable input for alkali activation. The geopolymers synthesized from brick fragments resulted in materials of supperior mechanical strength. A mixed use of fly ash and brick fragments failed to show a synergetic effect. Properties of the resulting geopolymers have been inferior to the properties of geopolymers produced using just fly ash or just brick body.
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The verification of durability of surface layer by pull-off testing
Fujačková, Hedvika ; Komárková, Tereza (referee) ; Kocáb, Dalibor (advisor)
The theoretical part of this bachelor's thesis defines the basic properties, categorization, and use of the individual components of concrete and presents the properties of fresh and hardened concrete, especially the tensile strength. Furthermore, the thesis addresses the problem of durability assessment of concrete, which depends directly on the quality of the surface layer. The experimental part of the thesis focuses on executing of a pull-off test and examines the surface layer tensile strengths of various concrete mix designs. The thesis examines how the results of the measurements correspond with other published results.
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Durability of alkali-activated systems
Šafář, Martin ; Šoukal, František (referee) ; Kalina, Lukáš (advisor)
Alkali activated binders have the potential to become an alternative construction material to ordinary portland cement binders. This thesis concentrates on durability testing of alkali activated blast furnace slag and fly ash based concrete. The chosen aspects of durability included sulfate resistance, acid resistance, carbonation, freeze-thaw resistance, frost-salt resistance and porosity. Microstructural changes and formation of new crystalline phases were observed using XRD and SEM-EDX analysis. Potential application of the tested material from the durability point of view was evaluated by comparison with a reference ordinary portland cement based concrete.
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Optimization of methods for determining the durability of wood coating systems
Škvařil, Michael ; Žák, Antonín (referee) ; Vaněrek, Jan (advisor)
The bachelor thesis deals with the optimization of methods for determining the durability of wood coating systems. The theoretical part deals with a detailed analysis of wood coating systems, including the specification of their composition, especially with a focus on modern water-borne coating systems. In the practical part an experiment was carried out, where on the selected types of coatings applied to lumber was performed analysis of selected durability parameters of coatings after exposure to short-term and long-term exposure to degradation factors
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Influence of interference fit on Rolling Bearing life
Tetour, Stanislav ; Prokop, Aleš (referee) ; Řehák, Kamil (advisor)
Master thesis is focused on the influence of interference fit on rolling bearing life. The first part of thesis deals with the theoretical knowledge, that is necessary for the solution. The influence of interference fit was investigated of inner ring on shaft and outer ring in housing bore for recommended tolerance classes. Interference fit was solved on cylindrical roller bearing and tapered roller bearing. Analytical and numerical approach was used for the solution. A static analysis of bearing was made using program ANSYS Workbench in numerical section. The output of analysis was maximum shear stress under the contact surface, which result is contact fatigue of bearing. Bearing life was determined by life factor, which indicates bearing life with interference fit compared to bearing without interference fit.
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Development of new types of composites for concrete rehabilitation with increased protection reinforcement
Taranza, Luboš ; Durica,, Tibor (referee) ; Dohnálek,, Pavel (referee) ; Bydžovský, Jiří (referee) ; Drochytka, Rostislav (advisor)
Around the world there is a great number of reinforced concrete structures, who´s life cycle, for which they were designed, is significantly shortened due to action of various aggressive environments, or due to defects created during the construction process. (i.e. insufficient steel reinforcement cover depth). One of the most common causes of problems in reinforced concrete structures is corrosion of steel reinforcement. It is necessary to repair structures degraded in this fashion and return them to their original state. We made a unique polymercement concrete repair system was developed with value added. Corrosion inhibitors, including the newly developed, are implemented into its polymercement matrix, which significantly limit the corrosive processes in all new materials. The principle of proposed solution is application of repair system on a corrosion damaged structure, and then the active substances in the repair material will penetrate into substrate concrete and protect corroded steel reinforcement. Another value added is the application of recycled raw materials into the proposed materials, which has indisputable environmental effect and simultaneously allows for improvement of some properties of the repair materials. Further was developed a new method for detecting corrosion inhibitors in concrete.
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Enhancement of HSS tools cutting performance with PVD coatings
Medek, Martin ; Sliwková, Petra (referee) ; Píška, Miroslav (advisor)
Diploma work describes speed drill steels and its qualities before and after coating by methods PVD (Physical Vapour Deposition). The theoretic part is concerned with thermic processing of speed drill steels and their qualities with regard to individual alloying elements contained and its mechanical features. Second part of the theoretic part is concerned with particular methods of coating by the help of PVD technologies, kinds of coating with regard to additional elements and their qualities and surface treatments of coated material before and after its coating. The goal of the experimental part was the confrontation of cutting power features of cylindrical four-fluted face mills with straight shank, from speed drill steels non-coated and coated in two basic modes of milling – down-feed method and upfeed method. The results of measurements were interpreted by the help of four basic pictures (source values, power analysis, specific values). The result of all the experiment is that the application of PVD coatings enabled the increasing of cutting speed (with preservation of other cutting requirements) and led to decreasing of cutting force and cutting enforcements and extended durability of cutters.
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