|
|
Education as a Way to Freedom in Philosophy of Jan Patočka
Kalina, Lukáš
TITLE: Education as a Way to Freedom in Philosophy of Jan Patočka AUTHOR: Bc. Lukáš Kalina DEPARTMENT: Social Sciences and Philosophy Department SUPERVISOR: doc. PhDr. Naděžda Pelcová, CSc. ABSTRACT: This master's thesis will show the concept of education as the way to freedom in the philosophy of Jan Patočka. It will deal with common phenomenological basis of philosopher to education for freedom and the concept of freedom, and also philosopher's viewpoint to the instrumental education and general link between instrumentality and free human beings. What means ''to raise/educate'' or ''to be raised/educated'' and how Jan Patočka thinks in the meaning of educational/raising methods. KEYWORDS: Upbringing, Freedom, Phenomenology, Three Movements of Human Life, Shake, Truth, Patočka
|
|
|
Action of organic additives in various alkali-activated binders
Markusík, David ; Kalina, Lukáš (referee) ; Bílek, Vlastimil (advisor)
This thesis explores the influence of admixtures (lignosulfonate plasticizer, hexylene glycol) on the rheology of AAM. With the characterized precursors, the rheology of AAM without admixtures is examined based on the chosen activator. Then the influence of the additives was measured. Rheological measurements were complemented by the determination of LS admixture adsorption on chosen precursors in solutions of NaOH, NaVS, and Na2CO3, and the determination of zeta potential of chosen plastified AAP. For comparison, measurements of cement pastes with the same admixtures were made in parallel to the AAM. the ability of plasticizer to improve the workability of slag and fly ash-based AAM when activated by NaOH was observed. No plastifying effect was found in MK-based pastes in none of the studied environments. The rheological measurements are in accord with most of the measured adsorptions and determined zeta potentials. In the case of hexylene glycol, the rheology of pastes is primarily influenced by the combination of precursors and admixtures. With hexylene glycol admixture the NaVS activator is inapplicable because silicates and hexylene glycol interact and worsen the rheological properties of the AAP.
|
|
|
Evolution of rheological parameters of platicized alkali-activateted slag in time
Krejčová, Marie ; Kalina, Lukáš (referee) ; Bílek, Vlastimil (advisor)
This diploma thesis deals with the development of the rheological properties of plasticized alkali-activated slag over time and depending on the timing of plasticizer and activator addition. These properties are very essential for the use of this material in practice. The main part of this work was oscillating measurements. Two types of measurements were performed – amplitude sweep and time sweep. The aim of the amplitude sweep was to determine the limit properties of the sample related to the destructive structure when the time sweep was continuous monitoring of the evolving structure. Furthermore, calorimetric measurements and solidification measurements were performed using a Vicat apparatus. The silica modulus activator and the method of adding the lignosulfonate-based plasticizer were changed for the individual mixtures. It was found that with the silica module 0 (activation with NaOH) the plasticizer works very well, better results were obtained with the addition of the plasticizer at the beginning of mixing and the activator only later. With increasing silica modulus, the importance of the presence of a plasticizer decreased.
|
|
|
On the efficiency of plasticizing admixtures in alkali-activated slag based system
Flídrová, Michaela ; Šoukal, František (referee) ; Kalina, Lukáš (advisor)
Alkali-activated materials (AAM) are construction materials with great potential, especially for their environmental friendliness, but also due to their mechanical properties. Therefore, it is appropriate to pay further attention to these binders. This diploma thesis deals with monitoring the effectiveness of plasticizers in connection with the surface chemistry of the alkali-activated slag system. Sodium hydroxide and sodium water glass were used as alkaline activators for the preparation of alkali-activated blast furnace slag-based systems. To study the effectiveness of the lignosulfonate plasticizer, yield stress, heat flow, adsorption and zeta potential were monitored depending on the amount and time that the plasticizer was added to the system. The results show that the type of activator used in the mixtures plays an important role. NaOH-activated samples revealed the best efficiency of lignosulfonate plasticizers. A key factor in studying the behavior of the studied mixtures was the measurement of the zeta potential, which provided insight into the surface charge of blast furnace slag particles related to the ability of lignosulfonate to adsorb on grains of alkali-activated slag.
|
|
|
Utilization of lignosulfonate plasticizer in alkali-activated materials
Zetocha, Martin ; Hrubý, Petr (referee) ; Kalina, Lukáš (advisor)
Tato bakalářská práce se zabývá využitím plastifikátorů na bázi lignosulfonátu v alkalicky aktivovaných materiálech. Sledován byl vliv na směs pasty aktivované vysokopecní strusky za použití hydroxidu sodného, vodního skla o různých modulech a uhličitanu sodného. Pozorován byl vliv plastifikátoru na bázi lignosulfonátu při zamíchávání do různých směsí, na zpracovatelnost, mechanické vlastnosti a reologii směsi. Důležitým faktorem byly použité aktivátory ve směsích. Nejlépe reagující směs na lignosulfonát se ukázala být za použití NaOH jako aktivátoru. Při pokusech pochopit reologické vlastnosti sledovaných směsí, jako klíčového faktoru chování těchto směsí bylo měření zeta potenciálu. Hodnoty zeta potenciálu nám daly bližší náhled na povrchový náboj častic vysokopecní strusky. Ten se prokázal jako klíčový faktor při posuzovaní účinnosti plastifikátoru. Tato zjištění budou vzata v úvahu a dále diskutovány v této práci.
|
|
|
Fixation of the lead in alkali activated materials based on different types of ashes
Cába, Vladislav ; Kalina, Lukáš (referee) ; Koplík, Jan (advisor)
The aim of this work was to develop an alkali activated matrix based mainly on fly ash, to determine the ability to fix lead in these matrices, the impact of added lead on mechanical properties and to reveal the way of lead fixation in these matrices. The matrices consisted mainly of fly ash (four from fluidized bed combustion, one pulverized coal combustion) with an admixture of blast furnace slag and sodium silicate as an activator. Lechates were prepared on the basis of the ČSN EN - 12457-4 standard, lead concentrations in them were measured using an atomic emission spectrometer with inductively coupled plasma. The strengths of the samples were measured after 28 days. Images, element maps and element spectra were taken to determine the structure using a scanning electron microscope with an electron dispersion spectrometer, the samples were analyzed on an infrared spectrometer with a Furier transform, X-ray diffraction analysis and electron spectroscopy for chemical analysis were also used. The individual measurements showed that lead is accumulated in the form of hydroxide. The impact of lead doping on strength of the matrix was different for individual samples. Matrices from both types of fly ash released minimal amounts of lead into leachates, so it is possible to use them to fixate lead.
|
|
|
Monitoring of alkali-silica reaction
Doležal, Martin ; Kalina, Lukáš (referee) ; Opravil, Tomáš (advisor)
Due to the alkali-silica reaction (ASR), concrete structures are damaged, which can lead to the loss of their useful properties. For the reaction to take place, the presence of alkalis is required. During the work, the release of alkalis into the pore solution was monitored. During hydration pore solutions were taken, on the basis of calorimetric curves. In pore solutions the K+ a Na+ content was analyzed by ICP-OES. The result is graphs of the development of alkali content and their relationship to cement hydration. The danger of the alkali in tested samples for the course of the reaction is described here. The description of the alkali content and its development is important for understanding the course of ASR and proposing a viable solution to protect against this problem.
|
|
|
Effect of curing conditions on shrinkage of alkali activated systems
Pragerová, Barbora ; Kotrla, Jan (referee) ; Kalina, Lukáš (advisor)
This bachelor thesis deals with the determination of optimal curing conditions of alkali-activated systems in order to reduce shrinkage. Hardened alkali-activated blast-furnace slag pastes activated by sodium silicate were tested in the empirical part. Six varieties of curing conditions were compared. Immediately after demolding process, three sets of samples were stored in air, water and plastic film. Another three sets were first placed in water for 14 days, then removed and two of them impregnate with lithium silicate and acrylate-based coatings. The formation and the number of cracks were monitored by an optical method. The percentage of cracks was evaluated by the ImageJ program. The highest number of cracks was formed after 7 days of curing, given the samples placed in the open air. Some them were filled later. Samples placed in the open air after being submerged in water for 14 days showed a rapid increase of cracks as well, but the percentage of cracks was reduced to 50 %. Treating agents reduced the development of cracks but have not stopped their formation. After 36 days of curing, the results of these types of curing conditions were comparable. Only the samples wrapped in plastic foil showed a minimum number of cracks and no cracks were observed if the samples were submerged in water. The lowest levels of shrinkage were reached with the samples placed in water, and with the ones wrapped in plastic foil. Samples stored in water for the first 14 days showed the identical tendency of high-level shrinkage, as did the ones placed in the open air.
|
|
|
Study of air-entraining admixtures in alkali-activated materials
Kiripolský, Tomáš ; Koplík, Jan (referee) ; Kalina, Lukáš (advisor)
Air entraining admixtures are surfactants, that are commonly used in Portland cement materials, because they form and stabilize small air bubbles distributed in the binder, thereby changing the pore size distribution. The aim of these additives is to increase the durability of the cured binder, especially in climatic conditions, where it must withstand low temperatures, and simultaneously improving the workability in the plastic state. The effect of air entraining admixtures in alkali-activated slag was studied for certain properties. Air entraining admixtures were able to entrain the air in the alkali-activated matrix, they changed the pore size distribution, which resulted in a reduction in capillary pressure in the porous complex, and there was a reduction of shrinkage under autogenous conditions, respectively. The improvement of workability is certainly also positive, but on the other hand there has been a bad effect on flexural strength and compressive strength. The morphology of the air entrained binder was observed by scanning electron microscopy, and simultaneously the effect of air entrained admixtures on hydration was observed by isothermal calorimetry.
|
|
|
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.
|
guest ::
