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Study of microstructure of autoclaved aerated concrete with using of secondary raw materials
Martanová, Jana ; Suchý, Peter (referee) ; Kulísek, Karel (advisor)
Autoclaved aerated concrete is a used building material, especially for its thermal insulating properties. During autoclaving, an aerated concrete microstructure produces crystalline CSH phases, primarily tobermorite. The ingoing substances are calcium oxide and silica. In addition to commonly used raw materials, secondary raw materials rich in silicon dioxide can be used for production. The use of secondary raw materials gives the opportunity for the construction industry to be more environmentally friendly. Another benefit is the reduction of financial costs. The work explores the influence of individual secondary raw materials on the microstructure. High-temperature fly ash, fluid fly ash, cinder, ground glass and zeolite were used The raw materials were mixed with unalloyed lime at a molar ratio of calcium oxide to silicon dioxide of 0.73 and 1.0. Autoclaving capsules were used to synthesize tobermorite under laboratory conditions. Autoclave was performed at 170 °C and 190 °C with hydrothermal durations of 4, 8 and 16 hours. The most important influence on the microstructure was high-temperature fly ash, on the contrary, the greatest influence on the mechanical properties is attributed to the ground glass.
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The Effect of Thermal Exposure of the Porosity and Mineralogy of Dense Silica Bricks.
Janek, Ondřej ; Kotouček, Miroslav (referee) ; Nevřivová, Lenka (advisor)
Silica bricks is a refractory building material which contains at least 93 % of silicon dioxide in polymorphic forms, mostly -tridymite, -cristobalite and unreacted -quartz. In glass industry is used for building crowns of glass tanks and in coke industry is used for building coke oven batteries. The advantage is the high refractoriness under load, high resistance to acidic melts. The disadvantage is the low resistance to changes in temperature below 600 °C. The thesis deals with the influence of repeated firing on the silica bricks and to its porous structure and mineralogical composition.
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Sands for the production of foundry moulds and cores
Ostrézí, Filip ; Rusín, Karel (referee) ; Cupák, Petr (advisor)
Bachelor thesis deals with properties of most usable sands in foundries and with their advantages, disadvantages and usability. Most used are silica sands, because of their low prices, but they have a lot of disadvantages like discontinued heat dilatation, acidit reaction and health defect. Mainly described are sands from Czech and Slovak Republic and few sands out of Europe. Non-silica sands don´t have so much disadvantages, but their problem is a big price. Most used non-silica and synthetic sands are described.
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Deformation and petrological record of polyphase quartzo-feldspathic rocks in Erzgebirge, Bohemian Massif
Kryl, Jakub ; Lexa, Ondrej (advisor) ; Závada, Prokop (referee) ; Hasalová, Pavlína (referee)
The Erzgebirge dome, exposing Proterozoic - Early Palaeozoic metagranitoids and metasedimentary rocks of the Saxothuringian domain in the Bohemian Massif, is formed by a tectonic stack of several UHP-HP and HT units exhumed during the Variscan continental subduction-collision process. A systematic study of orthogneiss deformation microstructures carried out on a regional scale has been done to evaluate these units' extent and relative structural position in the subduction complex. Five different microstructural types have been distinguished, revealing two overprinting sequences with 1) coarse-grained microstructures in the parautochthonous Kateřina-Reitzenhain Dome and 2) fine- grained microstructures in the allochthonous HP-HT Gneiss Eclogite Unit I. P-T conditions of the individual overprinting microstructures calculated by conventional thermobarometry suggest continuous deformation during exhumation along two contrasting P-T paths. The warmer one in the parautochthonous unit showed exhumation from ~13.5 kbar and ~820 ◦C to ~3 kbar and ~500 ◦C, while the colder one in the allochthonous unit showed exhumation from ~16 kbar and ~740 ◦C to ~3 kbar and ~400 ◦C. The overprinting microstructures are associated with vertical shortening interpreted as ductile thinning. This deformation started at depths...
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Physics of the H2O-weakening effect in deformation of quartz
Pongrac, Petar ; Jeřábek, Petr (advisor) ; Stipp, Michael (referee) ; Peč, Matěj (referee) ; Kronenberg, Andreas (referee)
In order to investigate the influence of H2O on relationships between mechanical behavior, microstructural properties, deformation mechanisms and H2O distribution in natural quartz aggregates, the Tana-quartzite samples were deformed with various quantities of added H2O. The samples were deformed in axial shortening setup (1) with constant conditions of 900 řC, 1 GPa and strain rate of ∼10−6 s−1 , (2) in strain rate stepping in interval ∼10−5 to ∼10−7 s−1 , and (3) in temperature stepping in interval 750 řC to 950 řC. The constant conditions experiments were carried out with added H2O in a range from 0 (as-is) to 0.5 wt%, while the strain rate and temperature stepping experiments were carried out using only as-is and 0.1 wt% H2O-added samples. With respect to their mechanical behavior, the samples after con- stant conditions experiments are grouped into low-H2O (0-0.2 wt% added H2O) and high-H2O (0.3-0.5 wt% added H2O). The low-H2O samples show relatively similar mechanical behavior, with 0.1 and 0.2 wt% H2O-added samples showing slightly lower strength compared to the as-is ones. Behavior of the high-H2O samples is more erratic and less systematic, dividing samples to the weaker ones and the stronger ones. Most of the strain in the weaker samples is localized in the vicinity of the thermocouple...
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Quartz microchemistry as metallogenetic indicator
Pacák, Karel ; Zachariáš, Jiří (advisor) ; Trubač, Jakub (referee)
Region surrounding the Central Bohemian Plutonic Complex represents one of the most important gold bearing zones in the Czech Republic. Several types of gold deposits dominated by hydrothermal quartz gangue were explored here and distinguished: the Intrusion related gold deposits ("Petráčkova hora" and "Mokrsko") and the orogenic gold deposits ("Jílové u Prahy" and "Kasejovice" ). Deposits "Libčice u Nového Knína" and "Roudný u Vlašimi" are partially similar to the orogenic gold type, but are different from other orogenic type deposits in the region. All together 38 samples from these five deposits were analyzed with laser ablation technique (LA- ICP-MS) to produce 228 measurements. Selected samples were selected to represent both main quartz gangue carrying the Au ore and latter weakly mineralized quartz gangue. Samples representing hydrothermal quartz gangue with no direct relation to Au-ore deposits were also collected in order to compare chemical composition of both quartz types originating from the same area. Main concern of this work was in-situ analysis of chemical composition of different generations of quartz gangue and statistical comparison of differences within individual deposits as well as comparing the examined deposits themselves. Total 65 isotopes were measured, trace element...
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Characteristics of polyphase deformation in quartz microstructure: an example from the Krkonoše-jizera Unit
Očenášková, Eva ; Jeřábek, Petr (advisor) ; Závada, Prokop (referee)
Quartzite samples taken in the east part of Krkonoše-Jizera Massif belong to metasedimentary cover of paraautochtonous unit. Rocks underwent a polyphase deformation which established a strong shape preffered orientation (SPO) of quartz grains. In folded quartz veins, deformation overprint mechanisms and microstructure, CPO and SPO relations were studied. For determination of crystal preffered orientations (CPO) the method of computer integrated polarization microscopy (CIP) was used. Microstructural analysis was focused on grain sizes, aspect ratios, long axis orientations and their relation to the deformation overprint grade. Results implies that dominant mechanism of quartz grain recrystallization is grain boundary migration. Folds were created by simple shear in microscale. The deformation overprint grade is strongest in the top of the fold hinge, where grains achieve highest aspect ratios and sizes. In the lower parts of the fold hinge the original CPO is preserved in small grains and SPO has similar orientation to original CPO. During folding CPO and SPO rotated with shear direction in dependance on deformation overprint grade.
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ASR potential of quartz in experimental mortar bar specimens
Kuchyňová, Markéta ; Kuchařová, Aneta (advisor) ; Vavro, Martin (referee)
The alkali-silica reaction is one of the most damaging chemical reactions taking place in concrete, which can cause fatal damage. ASR originates under following conditions: high moisture (> 80 %), sufficient amount of alkaline ions (Ca2+ , Na+ , K+ ) and use of reactive aggregates (low crystaline or deformed quartz, amorphous SiO2). Reactive aggretates react with high alkaline pore solution and produce hydrofile gels. These gels absorb water and swell. Dilatometric test methods are commonly used to evaluate the reactivity of aggregates. The principle of dilatometric test methods is simple. Mortar or concrete prisms are created in a laboratory, then they are stored in the special environment, which accelerates the inception of ASR. The creation and expansion of alkali-silica gels cause prism's length changes. The major goal of this diploma thesis was to evaluate the alkali-silica reactivity potential of quartz-rich rocks using microscopic (polarizing microscopy, scanning electron microscopy combined with SEM/BSE image analysis) and dilatometric (ASTM C1260, RILEM AAR-4.1) methods. Rocks were assessed as reactive, potentially reactive and non-reactive by the ASTM C1260 method. The reactivity of aggregates was connected with the amount of cryptocrystaline matrix, grain size, shape of grain boundaries,...
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