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Optimizing requirements for wood coatings
Bednářová, Ilona ; Petránek, Vít (referee) ; Vaněrek, Jan (advisor)
The work deals with wood coating systems. It is focused on the theoretical division of paints due to different aspects, moreover on testing of wood coating systems. In the practical part of the work, the experimental work regarding the influence of weather conditions onto durability of different wood coatings system was preceded. They were compared two different coatings within the basic tests in different environments.
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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 material base of coating systems onto wood durability
Bednářová, Ilona ; Petránek, Vít (referee) ; Vaněrek, Jan (advisor)
The thesis deals with the influence of the base material of the coating systems for wood durability when we exposed them to external conditions. The theoretical part is devoted to wood durability and weather resistance with a detailed description of the tests the durability of coating systems. A substantial part of the theory is devoted to description binder component of the coating material. In the practical part was performed the experiment, which examined the influence of the thickness of the coating system, the type of coating material (paint or lasure) as well as the type of binder (water dispersion with an alkyd or acrylic resin, respectively solution coating system with the alkyd resin). All coating systems were exposed to natural and artificial durability tests. The criterions for evaluation were chosen differences of colours.
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Modulus of elasticity of natural stone
Hoduláková, Michaela ; Cikrle, Petr (referee) ; Kocáb, Dalibor (advisor)
The value of the modulus of elasticity of concrete depends on the concrete composition (particularly on the aggregate used). The contemporary construction industry literature lacks comprehensive studies of the modulus of elasticity for each type of the rock stone. Therefore, this study focuses on testing and comparing the modulus of elasticity of selected types of rock stones used for the production of crushed coarse aggregates into the concrete. The modulus of elasticity are determined by static and dynamic methods. The work also deals with the modulus of elasticity of granite in different stages of weathering.
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The optimization of the wood polymer composite composition regarding its utilization in building structures
Benešová, Anna ; Pospíšil,, Ladislav (referee) ; Ďurica,, Tibor (referee) ; Bodnárová, Lenka (referee) ; Vaněrek, Jan (advisor)
Wood-polymer composite is a relatively new type of material that combines shattered wood mass and a thermoplastic polymer. This material is utilized especially as an alternative to hard wood in the area of non-bearing exterior elements, as it reaches better properties in terms of the basic durability and low maintenance. Raw material composition and processing of the composite enable to provide a significant modification with further matters leading to an improvement of the end-product properties. Research and development in this field focuses predominantly on the utilization of such modifying additives that either enhance the resistance to weathering or are of the recycled nature, as a significant part of the raw material mixture comprises the constituent obtained from non-renewable resources. The aim of the thesis is the evaluation of the influence of the wood-polymer composite modification separately at two levels. First of them is the modification to matrix by using a recycled polymer, the second one comprises the modification of the wood flour with a secondary spherical filler. Both types of modified composites have been assessed in terms pf the prime characteristics and the resistance to adverse ambient.
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Granites of Prague stone arch bridges in 19th c.: sources, properties, and weathering
Rauvolfová, Hana ; Přikryl, Richard (advisor) ; Krutilová, Kateřina (referee)
This thesis deals with the topic of the degradation of granite masonry, which was used for the construction of two stone arch bridges in Prague. Granite is used as a popular building material for its high durability however it is still necessary to check the condition of the masonry, especially in cities where stone is subject to different degradation process than stone in nature is exposed to. The first chapter is devoted to description of granite from a petrographic point of view, its physical and chemical properties and the important properties that makes it a popular building stone. Furthermore, the classification of granitic rocks and important quarries in Czech Republic is described here. The next chapter is dedicated to the description of the degradation process that negatively affect the rock. Degradation processes are divided into three categories: physical, chemical and biodegradation. Degradation processes are described here in general, but the results of tests performed when measuring degradation on granite historical buildings from abroad are also presented here. The last part of this thesis is dedicated to stone arch bridges, their most common faults and repair methods. They focus more on the two Prague bridges from the 19th century, the Legií bridge and the Palacký bridge, for the...
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Climate impact on archaeological monuments in Prague Castle
Pokorný, Šimon ; Weiss, Tomáš (advisor) ; Kozlovcev, Petr (referee)
This thesis deals with the question of the influence of climate on archaeological monuments beneath the pavement of the III. courtyard of Prague Castle. The complex archaeological site is threatened by the effects of several climatic factors, especially water and temperature changes, which cause weathering processes, and the historical building material in this area is subsequently degraded. The theoretical part of this thesis first deals with the study of historical building materials in the excavation area, with a focus on marlstone and clay slate, which are most susceptible to various types of weathering. Subsequently, degradation processes that affect the state of the present material are discussed, particularly processes related to water penetration through the material, chemical weathering caused by salt crystallization, and swelling of clay minerals, a process that often occurs in clay slate. The last chapter of the theoretical part outlines the impact of future climate change on the action of these processes. The practical part of this thesis focuses on research into frost and salt weathering cycles, particularly the determination of the frequency of cycles in one year of continuous measurement. Moisture and temperature values over time from sensors that are evenly distributed throughout...
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Influence of the stress field on weathering and erosion of sandstone landforms
Řihošek, Jaroslav ; Bruthans, Jiří (advisor) ; Mikuláš, Radek (referee) ; Válek, Jan (referee)
The influence of mechanical stress on weathering and erosion has been overlooked in works focused on sandstone landforms formation, although stress has been shown to be a key factor in the formation of a number of different sandstone landforms recently. The main goal of the doctoral thesis is to understand the relationship between mechanical stress and weathering or erosion in the formation and development of sandstone landforms. The influence of mechanical stress on the mode of weathering and the rate of disintegration of the material forming historical monuments in Petra, Jordan was investigated on the site and on samples in laboratory. A negative exponential dependence has been proven between the speed of salt weathering and the magnitude of uniaxial compression of Petra sandstone samples. The role of mechanical stress as a mechanism controlling the formation and development of the shape of sandstone forms was further studied in rock overhangs, sandstone arcades and rock gates in the Czech Republic and the USA. The doctoral thesis presents and verifies a method using Střeleč sandstone as a natural analogue in physical models simulating weathering and erosion of cemented sandstone. These physical models usually take the form of a reduced initial shape of a sandstone object created in situ from...
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Microforms of sandstone relief and their using in relative dating
Krbcová, Klára ; Křížek, Marek (advisor) ; Engel, Zbyněk (referee)
Microforms and mesoforms play the main role in the sandstone relief. Their origin is conditioned by some processes, the main are weathering and erosion. Based on the background research, the deffinition, classification, diagenesis and occurrence of sandstones was described. The second part of the bachelor thesis is focused on the mechanism of weathering and erosion. The microforms and mesoforms of the sandstone relief were divided into groups according to the guiding process of their origin. The description of the sandstone forms, the way of their origin, the stage of development and their extension were described. In the practical part of the bachelor thesis, the microforms in the gorge Apatyka in CHKO Kokořínsko were analyzed. The practical part was focused expecially on honeycombs, because their extension in the gorge is huge and they enable the complex analyse of their location in the gorge and in the rock outcrops. Using suitable methods it was found, that the honeycombs are located primarily in the eastern quadrant, their coverage decrease with the decreasing height of the rock outcrops and their presence in the lowest and the highest parts of the rock walls is limited. The second part of the fieldwork was focused on the relative dating of the parts of the gorge with honeycombs. The odlest part of the...
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Origin and evolution of silcretes
Kohoutová, Iveta ; Zachariáš, Jiří (advisor) ; Adamovič, Jiří (referee)
Summary: Silcretes are rocks with high content of SiO2 (usually more than 90 wt. %) formed by mobilization of SiO2 during weathering processes. Silcretes formed near the Earth's surface by soil weathering in warm and humid climate are termed as pedogenic silcretes. Another type of silcrete is groundwater silcrete, whose origin is usually associated with the groundwater table and depths of 5-50 m below the surface and arid to semi-arid climate. The third type of silcretes is associated with evaporites. Its genesis is complicated; as well it is difficult to date this silicification. There are four types of silcrete textures: GS-, F-, M-, C- textures; the most common is the F-texture. In the Czech Republic silcretes are more known under the term "sluňáky" or "quartzite". Indeed, in every country where they occur, have their own specific name. Silcretes are essentially composed of SiO2, minor constituents represent heavy minerals and/or feldspar. Cement is mostly α-quartz, chalcedony and opal. Average thickness of silcretes is 1-3 m, rarely 5 meters. Main source of SiO2 is chemical weathering of silicate minerals or quartz dust grains carried by wind and deposited on natural barriers, like blades of grass. There are two models of silcrete formation: lateral and vertical transport model SiO2. Sedimentary...
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