|
|
Effect of Cement Bypass Dust on Cracking Tendency of Alkali-Activated Slag during Drying
Krejčová, Marie ; Švec, Jiří (referee) ; Bílek, Vlastimil (advisor)
This bachelor thesis deals with the influence of bypass cement dust on cracking of alkali activated slag. Significant shrinkage and cracking prevent greater use of alkali activated slag. The length changes and strength of the mixtures with different amount of bypass cement dust were measured at various curing conditions. In these mixtures, cracks were observed and their amount was evaluated by image analysis. It has been found that the addition of dust can reduce the amount of cracks. Treating the prisms in a humid environment leads to a reduction of cracks, especially during long-term treatment. In order to improve flexural and compressive strength, it is preferable to use dust as a replacement for part of aggregates and not as a partial slag replacement.
|
|
|
Possibilities of utilization of brick-grind-dust in alternative binding systems based on fluidized ash
Tušla, Václav ; Švec, Jiří (referee) ; Opravil, Tomáš (advisor)
This bachelor´s thesis deals with usage of brick-grind-dust in alternative binding systems based on ashes of fluid combustion. Specifically it deals with fly ashes and softly milled bed ashes of brown coal combustion. Primarily thanks of content of free lime, anhydrite and other components, fluid ashes have binding properities. Brick-grind-dust arise in end formation of burned bricks. The aim of thesis is to verify, possibilities to create composite of appropriate abilities with high or even exclusive amount of fluid ashes and brick-grind-waste. The paper also deals with influence of some chemical modifying additive on this alternative systems.
|
|
|
Possibilities of using plasticizers and superplasticizers in alkali-activated systems
Langová, Markéta ; Švec, Jiří (referee) ; Kalina, Lukáš (advisor)
Bachelor thesis deals with the preparation and properties alkali activated blast furnace slag after addition of the different types of plasticizers and superplasticizers with the different weight percentage amount. The aim of this thesis is to find suitable plasticizers or superplasticizers which would improve both workability and mechanical properties of alkali activated blast furnace slag. The effect of these admixtures on compressive and flexural strength was determined. In conclusion the behaviour of plasticizing admixtures in alkaline environment through the infrared spectrometry is studied.
|
|
|
Possibilities of enhancement of kaolin whiteness by separation of components containing titanium
Vaculík, Josef ; Švec, Jiří (referee) ; Opravil, Tomáš (advisor)
Theme of the bachelor’s thesis is enhancement of kaolin whiteness primarily by removing titanium and iron. Titanium itself in the modification of anatase doesn’t decrease whiteness, more likely is the other way around. Unwanted modification is rutile, which is dark and it decreases substantially the whiteness of kaolin. The most significant impact on whiteness of kaolin has the iron (III) compounds that are usually contained with titanium in minor minerals in kaolin’s raw material. Main goal of thesis was to test the hydrothermal conditions on separation of parts containing titanium and iron from the kaolin’s material. Separation in the hydrothermal condition was performed by infusing kaolin in the solutions of acids of various concentrations. To find out the final whiteness of kaolin material after hydrothermal treatment was used UV-VIS method with reflective module and to find out the amount of iron and titan transferred to the solution of acids because of hydrothermal treatment was used ICP-OES method.
|
|
|
The effect of boron and its compounds on setting time of portland cement
Kratochvíl, Jiří ; Švec, Jiří (referee) ; Opravil, Tomáš (advisor)
The aim of this work is to study the influence of boron and its compounds, boric acid and borax, on hydratation of portland cement. The first part describes chemical composition of portland cement and reactivity of its components. The second part deals with hydratation of portland cement. The teoretical part ends with description of retardation of portland cement using gypsum or other sulphate options. The experimental part describes preparation of samples – cement paste – modified by addition of boron, boric acid and borax in diferent concentrations. Results are obtained by evaluation of calorimetric curves, mechanical properties and phase composition. The goal is to describe kinetics of targeted slowed down process of hydratation and to find such addition which would suspend setting of boron modified system entirely. Comparison of effects of each boron-containing compound is based on its concentration and on its kind.
|
|
|
Study of interaction of HA / biosklo based composites in simulated body fluid
Riša, Juraj ; Švec, Jiří (referee) ; Bartoníčková, Eva (advisor)
This work deals with bioceramic materials based of hydroxyapatite, bioglass and their composites. These materials are commonly used in medicine, especially as hard tissue substituents. They can be prepared by different types of syntheses, from which the most common were picked for this work – precipitation of hydroxyapatite and sol-gel method for bioglass. Thermal analysis and X-ray diffraction were used for characterization of prepared powders. This thesis studies mostly their features within the composite materials, which were foamed for better bone stimulation. Properties and possibility in bio application of materials is firstly studied through their interaction in simulated body fluids, which mimics ionic concentration of human plasma. Experimental part covers synthesis of ceramic powders, their characterization, preparation of mixtures and scaffolds foamed through in situ foaming, their sintering at ideal temperatures, characterization of porosity and phase changes due to sintering. Basic tests of apatite formation ability were provided by incubation of prepared scaffolds in simulated body fluid for 3, 7, 14 and 21 days and their assay in scanning electron microscopy. Changes in concentration of Ca2+ a PO4 3- ions as well as in weight of the specimen were tracked within the incubation period.
|
|
|
Combined aluminium-silicon based sol-gel binding system for refractory
Taraba, Vojtěch ; Koplík, Jan (referee) ; Švec, Jiří (advisor)
The following piece of work deals with the use of a combined aluminium-silicon based sol-gel binding system for refractory. The effect of different gelling agents on the gelation process was observed and rheometric measurements were performed for MgO. After optimizating the drying process, the resulting gel was characterized by thermal analyses, based on which the firing temperatures were selected. Qualitative analysis of the gels fired to the selected temperatures was performed using FTIR. Using XRD, the semi-quantitative phase composition of the samples was monitored as a function of firing temperature. The topography of the test bodies prepared based on results of the previous analyses was later observed using a scanning electron microscope.
|
|
|
Evaluation of properties of lime mortars
Babíková, Barbora ; Švec, Jiří (referee) ; Opravil, Tomáš (advisor)
This bachelor thesis deals with evaluation of properties of lime mortars and their application in field of restoration and preservation of cultural heritage. The aim of this works is to compile evaluation line of different types of lime mortars based on comparison of their behavior during testing of their characteristic properties and resistance. Studied properties like setting time, compressive strength, tensile strength in bending, frost resistance, reactivity, content of free lime, loss of mass on ignition, point to applicability of given mortar in different interior or exterior conditions. The results of individual tests are further processed and evaluated.
|
|
|
Phosphate Binders in Refractory Application
Švec, Jiří ; Drábik, Milan (referee) ; Lang, Karel (referee) ; Havlica, Jaromír (advisor)
The doctoral thesis is focused on the study, research and development of refractories with phosphate bonding. Primary motivation is preparation of phosphate-based binders that can be applied for non-shaped insulating material fabricated by “in situ” foaming. The phosphate binders based on Al2O3-H3PO4 system are one of the most common in refractory technology. The amphoteric nature of the aluminium and its oxides require the setting of Al2O3-H3PO4 binders under the higher temperatures. Application of higher temperatures is necessary to obtain the minimal manipulation strength of as-prepared green bodies. The main goal of the work is preparation of ytrium phosphate-based binders via different preparation techniques. Yttrium based binders would allow phosphate refractory preparation by standard way, i.e via reaction between binder and reactive aggregate, without structural disintegration of foamed material even before getting manipulation strength or the final firing procedure. Yttrium is more basic than aluminium and therefore more reactive in Y2O3-H3PO4 system.. Yttrium oxide is highly refractory material and sintered yttrium monophosphate has excellent properties from the thermal and corrosive stability point of view. This fact should compensate higher price of this material. Experimental part of this work studies the possibilities of binders preparation in Y2O3-H3PO4 system. The mixtures were designed to prepare binding phase Y(H2PO4)3. Products of these reactions were characterized in phase and chemical point of view. In order to study and describe setting and hardening processes of phosphate binders, the products were “in situ” analyzed by the thermal analyses and high-temperature diffraction analysis up to the 1300 °C. High temperature products were then characterized by means of phase and chemical composition and morphology.
|
|
|
Synthesis of ceramic materials based on Ca-Co-O system
Žáková, Kateřina ; Švec, Jiří (referee) ; Bartoníčková, Eva (advisor)
In this work synthesis of structure cobaltites based on Ca-Co-O system is discussed. As major way of synthesis was chosen citric acid method. The document is devided into theoretical and experimental part and also into discussion of observed results. Main focus of literary research is general utilization and function of thermoelectric materials, related thermoeletric effects according to structural defects in crystals. Also topic of cobaltite ceramics is described. Due to the fact that calcium-cobalt oxides are conductive, their use is point of interest in high-temperature and energy applications. During experiments differential thermal and thermogravimetric analysis (TG-DTA), X-Ray diffraction, heat microscopy and scanning electron microscopy were used.
|
guest ::
RSS feed.