National Repository of Grey Literature 117 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
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.
Characterization and Pozzolanic Activity of Waste Expanded Perlite
Hermann, Radek ; Sedlačík, Martin ; Figala, Petr ; Kalina, Lukáš ; Havelka, Lukáš
This paper deals with characterization of multiple waste expanded perlites (WEP) from local central European sources with an emphasis on their suitability for use in cement composites. Influence of the milling time on their properties was studied. Both raw and milled WEP samples were thoroughly characterized in terms of their physical properties, composition, particle size, specific surface area, and pozzolanic activity. The findings affirm their potential as supplementary cementitious materials.
Study of carbonatation in alkali activated systems
Suchý, Rostislav ; Koplík, Jan (referee) ; Kalina, Lukáš (advisor)
The carbonation of the building materials based on the ordinary Portland cement is relatively well-known and extensively studied phenomenon. Conversely mechanism, reaction products and factors affecting the carbonation of the alkali activated materials are still not sufficiently clarified. In this work, the progression of the carbonation of the alkali activated materials under different conditions was investigated. The reaction products and the microstructural changes were determined by XRD respectively SEM-EDX analysis. The corrosive conditions due to the decreasing of the pH of the binders by the carbonation were observed by XPS analysis of the steel fibers. The carbonation of the alkali activated samples was compared with the reference samples based on the Portland composite cement. Besides these analyzes, the mechanical properties of the binders were monitored.
Metallography of stainless steels
Hasoňová, Michaela ; Kalina, Lukáš (referee) ; Zmrzlý, Martin (advisor)
This thesis deals with metallography of stainless steels. At the beginning of theoretical part the history of metallography is shortly summarized. Then the basic knowledge about metallography, ways and methods of preparing samples for subsequent analysis of structure are resumed. There are also summarized methods for examining the macrostructure and microstructure of materials with a particular focus on stainless steels. The literary-search section summarizes recent advances in the study of the structure of materials using methods of metallography. The task of the study was to find suitable composition of etchant to reveal the structure of stainless steels in order to achieve high quality and especially reproducible results.
Utilizazion possibilities of bricks grinding waste in alkali activated systems
Dzurov, Matej ; Kalina, Lukáš (referee) ; Šoukal, František (advisor)
The bachelor’s thesis deals with usage of brick grinding waste, arising from the grinding process of modern bricks, as a constituent of alkali activated binders. The aim of the thesis is to verify the properties of brick grinding waste and to test mechanical properties of mixtures with different proportions of brick grinding waste and ground-granulated blast furnace slag, activated by commonly available hydroxides and combinations of hydroxides and water glasses. Furthermore, the effects of temperature increase on properties of prepared test samples were investigated and formation of carbonate effluent was observed.
Industrial sludges as alternative fuel in cement plant
Raška, Miroslav ; Kalina, Lukáš (referee) ; Opravil, Tomáš (advisor)
This thesis deals with the use of industrial sludge as an additive to alternative fuels in the cement industry. The first part is focused on solid alternative fuels, especially sewagesludge, processed and used in the firing process of Portland clinker and heatingpotential of the secondary raw materials, fuels. The second part deals with the history, production of cement and its raw material base. The last part contains information of practical measurements and draw conclusions about the appropriateness of using that type of industrial sludge in cement as a solid alternative fuel.
Surface treatment of cementitious systems by silicate sealers
Iliushchenko, Valeriia ; Šoukal, František (referee) ; Kalina, Lukáš (advisor)
Impregnace na bázi silikátů se široce používá k ochraně betonu před agresivním prostředím. Pochopení aspektů týkajících se tohoto typu impregnace však není zcela jasné. Tato práce představuje informaci o jednotlivých vlastnostech vybraných křemičitanů, přesněji draselného, sodného, lithného a koloidního oxidu křemičitého (koloidní silika), dále o účinnosti z hlediska nasákavosti, stupni účinku na hydrataci cementu, schopnosti těchto látek uzavřít póry a jejích vliv na mikrostrukturu cementového substrátu a na penetrační schopnost. Účinnost filmotvorných látek byla hodnocena jak na čerstvém cementovém tmelu, tak na vyzrálejším, aplikovaných po 1 a 24 hodinách od smíchání směsi. K dosažení kvalitativních výsledků byly použity instrumentální metody, jako je rtuťová porosimetrie, rheometrie, izotermální kalorimetrie, rentgenová difrakční analýza a skenovací elektronová mikroskopie. S ohledem na provedené testy byla prokázána určitá účinnost ošetřujících přísad. Výsledky všech testů ukázaly vyšší účinnost těchto látek v případě ošetření na vyzrálejším cementovém povrchu, což bylo pravděpodobně způsobeno vyšším stupněm hydratace, díky čemuž se vytvořily nové fáze, se kterými silikáty byly schopné zareagovat a jistým způsobem ovlivnit mikrostrukturu.
The admixtures which are influencing setting time of portland cement
Hlaváček, Jaroslav ; Kalina, Lukáš (referee) ; Opravil, Tomáš (advisor)
During the production of concrete is important the careful selection of raw materials. Nowadays, we are trying in the production to minimize the economic burden and to maximize the use of secondary raw materials. This work is focused on the use of secondary raw materials from the energy industry in construction for the preparation of hydraulic binders. As the main raw materials were used different power plant fly ash from fluidized combustion. The composition of these secondary materials is quite different from conventional high-temperature ash, due to mixing with water they solidify and harden. Experiments were performed with three lodge fly ash from electrostatic precipitators of the fluidized combustion and one high-temperature fly ash. This work is focused on the possibility of monitoring the use of these secondary materials in construction, especially when tests were evaluated characteristics of strength and speed of setting and hardening.
Study of alkali-silica reaction in hybrid systems
Bradová, Lada ; Bílek, Vlastimil (referee) ; Kalina, Lukáš (advisor)
This study evaluates question of alkali–silica reaction (ASR) in hybrid system, which was designed in the bachelor's thesis, to meet the requirements of EN 197-1 and classified to the Blastfurnace CEM III/C cements. The durability of this system is a great unknown. For this reason, the same methods (ASTM C1260, ASTM C289 and ASTM C856) were used to observer the ASR effects as the ones used to observer the Portland cement based concrete. Supplementary methods include determination of compressive strengths according to EN 196-2 and scanning electron microscopy to observe the microstructure. Hybrid system results were compared to two different types of cements, CEM I and CEM III/B. From the results of the ASR evaluation assays, it was found that the hybrid system (CEM III/C-HB) and CEM III/B showed the lowest tendency to ASR. The results of the supplementary methods showed that CEM III/C-HB compressive strength increases after 14 days within NaOH by 43 % in comparison to 28 days strength. Based on those results, it is sure that the CEM III/C-HB shows little susceptibility to ASR.
Development of shrinkage reducing admixtures designed for alkali activated materials
Šístková, Pavlína ; Bílek, Vlastimil (referee) ; Kalina, Lukáš (advisor)
This thesis deals with development of shrinkage reducing admixtures designed for alkali activated materials based on blast furnace slag. The main task of this work is to select the most suitable shrinkage reducing admixture based on experiments, in which can be observed minimal shrinkage and at the same time it will not adversely affect the properties of alkali activated blast furnace slag. In the experimental part of the work, test beams containing shrinkage reducing admixtures were prepared, in which the shrinkage and loss of weight were measured. Moreover, the mechanical properties of individual beams, such as tensile strength and compressive strength, were measured. Next, the surface tension of individual shrinkage reducing admixtures was measured in a mixture with pore solution. The hydration process of alkali activated materials under the action of reducing shrinkage admixtures was monitored by calorimetric analysis. The microstructure of the prepared samples was observed by scanning electron microscopy.

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1 Kalina, L.
5 Kalina, Ladislav
4 Kalina, Leoš
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