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Inhibition of hydrogen evolution in aluminum-phosphate refractory binders
Bednárek, Jan ; Kalina, Lukáš (referee) ; Šoukal, František (advisor)
The thesis deals with the possibilities of inhibition of the reaction of aluminium-phosphate binders with wear iron, which is contained in bauxite. This material is mixed with phosphate binders to form refractories. The hydrogen is produced by this reaction causing the mixture foaming. The amount of evaluated hydrogen was observed by the measuring by the Jank’s calcimeter. Also the shape of oxidation-reduction potential of the binders was measured before and after mixing with aggregate, using potentiometer. The influence of the addition of various cations on the hydrogen evolution and on the oxidation-reduction potential was observed. The effectiveness of the inhibitors was studied also visually by forming test elements.
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Utilization of by-pass cement kiln dust in alkali activated materials
Kiripolský, Tomáš ; Beranová, Denisa (referee) ; Kalina, Lukáš (advisor)
By-pass cement kiln dust (CKD) is a fine grained by-product of Portland clinker manufacturing. Its chemical composition is not suitable for the returning back into the feedstock and therefore has to be discharged. Such the increasing waste production contributes to lowering of the environmental impact of cement industry. The possible solution for the ecological processing of CKD is its incorporation into alkali activated blast furnace slag binders. Thanks to the high alkaline content, CKD serves as an effective accelerator for the latent hydraulic substance and at the same time solves the significant shrinkage of alkali activated materials which considerably limiting their practical applications. It was found out that the suitable amount of CKD (20 % replacement of slag) in combination with sodium carbonate increases the compressive strength development of about 10 % and reduces the drying shrinkage (11 % reduction). On the other hand this type of inorganic admixture accelerated the hydration process resulting in rapid loss of workability and shortening the initial setting time. The mechanism of action of CKD in alkali activated matrix has been investigated as well as its optimal dosage in the means of mechanical properties.
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The technology of aerated concrete
Zezulová, Anežka ; Kalina, Lukáš (referee) ; Opravil, Tomáš (advisor)
The technology of aerated concrete is a topic that is permanently studied and developed because of the incessant demand for a building material which ensures relatively high strength at low volume weight. This bachelor’s thesis examines the influence of replacing a part of sand with another silica material – microsilica. The increase of mechanical strength is expected at the same volume weight. Microsilica contents around 98 % of amorphous silicon dioxide with a high specific surface area that is substantially higher than a specific surface area of a ground sand. The reactivity of silicon dioxide increases with a higher specific surface area and also with the creation of a mineral tobermorite, which is the keeper of the strength in autoclaved aerated concrete. Three types of microsilica were chosen to examine the influence of replacing a part of sand with microsilica according to their availability for manufacture: microsilica Sikron and Elkem 971 U, microsilica Grace Davison was tested only marginally. Tests were carried out to determine volume weight, compressive strength, phase composition (by X-Ray diffraction method), and the content of tobermorit (by TG-DTA method).
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Impregnation of stainless steels for the conditions of oversea sailing
Chára, Tomáš ; Kalina, Lukáš (referee) ; Zmrzlý, Martin (advisor)
This thesis deals with temporary corrosion protection of stainless steel for the conditions of oversea sailing. At first the theoretical part describes types of the stainless steels focusing on their corrosion resistance and negatively or positively impacts affect of their resistance. There is also a proposal of methods of the temporary corrosion protection and testing its effectiveness. The recherché are summarized knowledge in testing resistance of stainless steels to pitting corrosion. The task of the study was to test the effectiveness of three different preservatives and comparing the quality of their temporary corrosion protection compared with unprotected chemically passivated stainless steels.
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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.
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On the mechanisms of shrinkage reducing admixtures in alkali activated materials
Komosná, Kateřina ; Bartoníčková, Eva (referee) ; Kalina, Lukáš (advisor)
This thesis is focused on the principles of behavior of shrinkage reducing agents (SRA) in alkali-activated materials based on blast furnace slag. The main focus of this work is selecting the most suitable admixture based on experiments, by which will be achieved through minimal shrinkage and will have negative effect on the properties of alkali-activated blast furnace slag at the same time. In experimental section of this work, the surface tension as individual additives as their mixtures with pore solution were measured primarily. Then the testing samples composed of blast furnace slag, water glass and addition of SRA were prepared. Of these samples was measured shrinkage and weight loss. Moreover, their mechanical properties such as flexural and compressive strength were monitored. Next, the beginning and the end of solidification was studied using the Vicat device and last but not least workability. The hydration process of alkali-activated materials with SRA was measured calorimetrically. Finally the microstructure in prepared samples was observed using scanning electron microscopy (SEM-EDS) and the total porosity was determined by mercury porosimeter.
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Comparision of leachability of heavy metals from various types of alkali-activated alumino-silicate systems
Smolková, Miroslava ; Kalina, Lukáš (referee) ; Koplík, Jan (advisor)
The work deals with the determination and comparison of leaching of heavy metals from various types of alkali-activated alumino-silicate systems (high-temperature fly ash, blast furnace slag). Such alkali activated materials are capable in their structure effectively encapsulate heavy metals, toxic chemicals or other contaminants, which can be beneficial for the environment. The aim of this work is to obtain a mixture with acceptable mechanical properties that could be useful for the inhibition of these substances. Leachability was tested according to norm ČSN EN - 12457-4, followed by analysis by ICP-OES. The structure of the matrix was investigated using SEM equipped with EDS.
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Reduction of hexavalent chromium in cement binders
Hrubý, Petr ; Šoukal, František (referee) ; Kalina, Lukáš (advisor)
The issue of hexavalent chromium contained in cement binders and the possibilities of its reduction are very current, due to the toxicity of Cr (VI) and constantly stricter regulations of the EU. The effort of achieving a cement binder with Cr (VI) concentration lower than 2 ppm and keeping this concentration unchanged during the long term storage is a frequently studied issue which needs to be solved. Requirements are put on the low cost for industrial use and without inducing changes of final properties of cement binders. A reducing agents based on iron (II) sulphate monohydrate potentially combined with some additives were studied in this study. The efficiency of reducing agents was analysed by commonly used UV-VIS spectrophotometry technique which uses 1,5-diphenylcarbazide as an indicator. The influence of added reducing agent on the mechanical properties was noticed by compressive strength test.
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Stainless steels
Chára, Tomáš ; Kalina, Lukáš (referee) ; Zmrzlý, Martin (advisor)
This thesis deals with stainless steels. The theoretical part describes the mechanisms and types of corrosion. Then the thesis deals with the properties, distribution and manufacture of the stainless steels and a brief description of the XPS method used for the practical part. In the recherche section summarizes the ways of using the XPS method for determining the quality of the passive layer of stainless steels eaten in different environments. Practical task was to compare the quality of the passive layer of stainless steels resulting from natural and chemical passivation.
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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.
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