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Gelation of waterglasses depending on their composition
Otřísalová, Pavlína ; Kalina, Lukáš (referee) ; Bílek, Vlastimil (advisor)
This bachelor thesis studies how are gelation of sodium and potassium silicates (water glass) influenced by their composition. The main goal of the thesis was to investigate the effect of silicate concentration, molar ratio, and alkaline ions on the gelation time. Qualitative analysis of obtained gels was also performed. The thesis includes literature research in the field of chemistry of silicate sols and gels. In the experimental part were prepared samples of both sodium and potassium silicates with silicate concentrations of 15 M and molar ratios of 0,53,0. Gelation was induced by adding calcium ions. Gelation time was measured using rheological oscillation tests (time sweep) and visual method. Qualitative analysis of the gels was performed using rheological oscillation tests (amplitude and frequency sweep) and visual method. Three significant trends were observed: 1) NaVS samples always had shorter gelation time than KVS samples 2) the higher the silicate concentration the higher the gelation time 3) gelation time of samples with molar ration of 2 was most influenced by silicate concentration. It was also observed that the formation of gel network was promoted in systems with 1) higher molar ratios 2) higher silicate concentrations 3) presence of K+ ions. Gels with molar ratios 2 were significantly weaker than those with ratio of 2,5 or 3,0.
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Průša, David ; Žižková, Nikol (referee) ; Čermák, Jan (referee) ; Šuhajda, Karel (advisor)
In construction practice, microwave radiation is widely used for drying building materials, remediating damp masonry or sterilizing biotic pests that have invaded building structures. Another, albeit less frequent, use may be, for example, in accelerating the solidification of materials and components, where the time required to obtain the handling strength is reduced due to the effect of microwave radiation. The available scientific and technical literature indicates that some materials, such as brick elements, do not change their physical and mechanical properties when exposed to microwave radiation for moisture remediation, although this has not yet been sufficiently verified, and, in contrast, that there is a significant change in properties when microwave radiation is used to accelerate the setting of fresh mixtures, such as those containing a cementitious binder matrix. This thesis builds on many years of research in the area, complements and refines existing information, provides new insights into the mechanical and physical properties of commonly available building materials that have been exposed to controlled microwave radiation, and compares them with reference values. It also provides an opportunity for further experiments that can build on this research. The experimental research was conducted on two independent sets of samples. The first experiment was carried out on a set of clay brick samples, using tests according to European standards, and focused on the effect of microwave radiation on compressive strength and water absorption. The experimental specimens were exposed to moisture followed by exposure to microwave radiation for drying and then compared with reference specimens. The data from these experiments suggest that microwave radiation can be used for the rehabilitation of brick elements and there is no significant change in the resulting mechanical properties with respect to the initial condition. The second experiment was carried out on a set of concrete mixtures, where the curing process was accelerated using microwave radiation, and the mechanical and physical properties obtained were compared with those of reference specimens. The data from this experiment suggest that microwave radiation can be used to accelerate the curing of concrete specimens, thereby obtaining the handling strength in a relatively short time, but a reduction in the resulting strength can be expected compared with reference specimens.
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Composite materials with silica matrix in the environment of high temperatures
Lisztwanová, Ewa ; Luňáček,, Martin (referee) ; Bydžovský, Jiří (advisor)
This thesis deals with the study and design of composite materials based on silica matrix suitable for extreme conditions, eg. for the repair of concrete structures with anticipated increased risk of fire. The theoretical part summarizes basic knowledge concerning the fire resistance of structures and the behavior of the composite system during extreme conditions. Theoretically oriented section also contains information on alkali-activated materials and their use in high temperature environments. Based on the evaluation of the theoretical part of the experiment were designed and tested different types of composite materials with increased content of raw materials from alternative sources. Laboratory research has been based on testing of basic physico-mechanical parameters including phase composition and microstructure of the proposed formulations before and after thermal exposure of 1200 ° C. Also considered was the effect of different cooling conditions.
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Research and development grout and anchor masses
Žlebek, Tomáš ; Petránek, Vít (referee) ; Drochytka, Rostislav (advisor)
Modern anchor and grout systems are now at a high level and they are used in many branches of industry. This thesis evaluates the current state of anchoring and grouting systems, research of currently used material basis, testing procedures and up to date legislation for these types of materials. Above all, the thesis is focused on the chemical types of anchor and grout materials for utilization in industrial production facilities with exposure to extreme loads, a new methodology for testing of these types of materials and input raw materials will be proposed. The final part of this thesis is a proposal of new optimum formulas for anchoring and grouting materials for utilization in industrial production facilities with exposure to extreme loads including the description of their applications.
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Complete insulation system for high temperature using secondary raw materials
Mészárosová, Lenka ; Ďurica,, Tibor (referee) ; Kolář,, Karel (referee) ; Kulísek, Karel (referee) ; Drochytka, Rostislav (advisor)
This work deals with the development of new types of insulating materials for use in the higher temperature. The area of application of these insulation materials is especially industrial chimneys, where the exhaust gases achieves 85 to 200 °C, furthermore it is industrial boilers and furnaces with surface temperature to 500 °C. In the introduction is presented the current knowledge in the field of insulating materials in the Czech Republic and in the world. Then the work is dealing with proposal of possible raw materials and suitable formula. According to purpose of use is the work divided into two parts – high temperature insulation for simple and for complicated shapes conditions. The sub-sections are divided to different possibilities of performance. The aim was, based on the scientific expertise of other authors in the world, design a new insulation system and redound to deepening scientific knowledge in the area of lightweight materials on the silica basis and to the extension of the offer of new products in building and industrial practice.
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Silicate Conductive Composites with Graphite Fillers
Baránek, Šimon ; Drochytka, Rostislav
Electroconductive composites are modern materials that are commonly used in many industries such as construction industry and machine-building industry. For example, these materials can be useful as sensors for monitoring changes in constructions, shielding stray currents from electrification networks, shielding electromagnetic radiation in operating rooms, cathodic protection against moisture or overvoltage protection of buildings. The topic of this post is the research of electrically conductive silicate composites with graphite-based fillers. In this research, composites with different ratios and types of graphite were tested and electroconductive properties such as impedance were monitored, as well as physical-mechanical properties such as strength. It was found that by adding 10 wt. graphite into the mixture reduces the impedance of the composites by 50 % and the compressive strength is reduced by approximately 40 %.
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Complete insulation system for high temperature using secondary raw materials
Mészárosová, Lenka ; Ďurica,, Tibor (referee) ; Kolář,, Karel (referee) ; Kulísek, Karel (referee) ; Drochytka, Rostislav (advisor)
This work deals with the development of new types of insulating materials for use in the higher temperature. The area of application of these insulation materials is especially industrial chimneys, where the exhaust gases achieves 85 to 200 °C, furthermore it is industrial boilers and furnaces with surface temperature to 500 °C. In the introduction is presented the current knowledge in the field of insulating materials in the Czech Republic and in the world. Then the work is dealing with proposal of possible raw materials and suitable formula. According to purpose of use is the work divided into two parts – high temperature insulation for simple and for complicated shapes conditions. The sub-sections are divided to different possibilities of performance. The aim was, based on the scientific expertise of other authors in the world, design a new insulation system and redound to deepening scientific knowledge in the area of lightweight materials on the silica basis and to the extension of the offer of new products in building and industrial practice.
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Composite materials with silica matrix in the environment of high temperatures
Lisztwanová, Ewa ; Luňáček,, Martin (referee) ; Bydžovský, Jiří (advisor)
This thesis deals with the study and design of composite materials based on silica matrix suitable for extreme conditions, eg. for the repair of concrete structures with anticipated increased risk of fire. The theoretical part summarizes basic knowledge concerning the fire resistance of structures and the behavior of the composite system during extreme conditions. Theoretically oriented section also contains information on alkali-activated materials and their use in high temperature environments. Based on the evaluation of the theoretical part of the experiment were designed and tested different types of composite materials with increased content of raw materials from alternative sources. Laboratory research has been based on testing of basic physico-mechanical parameters including phase composition and microstructure of the proposed formulations before and after thermal exposure of 1200 ° C. Also considered was the effect of different cooling conditions.
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Research and development grout and anchor masses
Žlebek, Tomáš ; Petránek, Vít (referee) ; Drochytka, Rostislav (advisor)
Modern anchor and grout systems are now at a high level and they are used in many branches of industry. This thesis evaluates the current state of anchoring and grouting systems, research of currently used material basis, testing procedures and up to date legislation for these types of materials. Above all, the thesis is focused on the chemical types of anchor and grout materials for utilization in industrial production facilities with exposure to extreme loads, a new methodology for testing of these types of materials and input raw materials will be proposed. The final part of this thesis is a proposal of new optimum formulas for anchoring and grouting materials for utilization in industrial production facilities with exposure to extreme loads including the description of their applications.
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