National Repository of Grey Literature 18 records found  1 - 10next  jump to record: Search took 0.00 seconds. 
The influence of admixtures on the hydration of Calcium Aluminate phases
Skalík, Martin ; Másilko, Jiří (referee) ; Koplík, Jan (advisor)
This thesis focuses on the effect of admixtures on the hydration time and on the formation of hydration products of calcium aluminate cement and its phases. Three main calcium aluminate phases, CA, CA2 and C12A7, were prepared to study using a high temperature sintering method that was optimised to be as fast as possible. The admixtures used were LiCl, NaCl, sodium tetraborate and citric acid. Prior to the actual hydration, the optimization of the admixture dosage was performed by Vicat test on two commercial aluminate cements, Secar 71 and Secar 80. The hydration with the right amnout of admixtures was monitored by heat flow calorimetry. Hydration products were investigated by X-ray diffraction analysis, Fourier transform infrared spectroscopy and electron microscopy.
Preparation of calcium-aluminate phases
Ohaňka, Zdeněk ; Novotný, Radoslav (referee) ; Koplík, Jan (advisor)
This work focuses on the preparation of calcium aluminates by solid state synthesis and by sol-gel method. Phases prepared were monocalcium aluminate (CA), dodecacalcium heptaaluminate (C12A7), tricalcium aluminate (C3A) and calcium dialuminate (CA2). Two modifications of sol-gel method were used – the difference between them was in the addition of EDTA. Each method was closely described and results were compared according to the achieved purity of prepared phases. X-ray diffraction analysis was used to determine the purity of prepared calcium-aluminates.
High-strength macrodefect-free composites for refractory applications
Ryšková, Martina ; Másilko, Jiří (referee) ; Šoukal, František (advisor)
The subject of the bachelor thesis is the study of heat-resistant macrodefect-free (MDF) cements based on calcium-aluminate cement and organic polymer polyvinylalcohol. Macrodefect-free cements are particularly important in excellent mechanical parameters, which include tensile strength in bending. These materials are characterized by their low porosity and the absence of microcracks. The main role of the MDF cements takes binding and non-flush interaction with polymer cement, which affect the chemical and physical-mechanical properties. The main problem in applying the MDF cements is the low water resistance. To prepare macrodefect-free samples were used calcium-aluminate cement (SECAR 51, SECAR 71) and polymer polyvinyl Gohsenol GH 17S. They were observed changes in mechanical properties depend on the type of curing samples were cured at laboratory temperature and 70°C. Samples annealed at 1000 ° C and then tested for tensile strength in bending before and after annealing, compared to mechanical properties. Thermal stress was tested by doping a microscope TGA-DTA-EGA and TMA analysis.
MDF composites AC-PVAl with increased moisture resistance
Repka, Martin ; Brandštetr, Jiří (referee) ; Šoukal, František (advisor)
Polymerem impregnované cementové materiály představují zajímavou a perspektivní alternativu klasických portlandských cementových past. Hlavním zástupcem těchto materiálů jsou macrodefect-free (MDF) kompozity, složené z anorganického pojiva a organického polymeru. I přes řadu vynikajících mechanických vlastností je plné zavedení MDF kompozitů na trh omezené především z důvodu jejich relativně nízké odolnosti vůči vlhkosti. Jednou z možností jak zvýšit odolnost výsledného MDF vůči vlhkosti je „in situ“ síťování polymeru. V této práci byla připravena počáteční série MDF kompozitů na bázi hlinitanového cementu a polyvinylalkoholu se třemi typy organo-titanátových síťovacích činidel (Tyzory). Efekt modifikace MDF kompozitů byl hodnocen na základě zkoušek pevnosti v tahu za ohybu po uložení materiálů v různých vlhkostních podmínkách.
Study of durability of binders concept on purposeful creation of ettringite
Sokolt, Stanislav ; Štenko,, Miroslav (referee) ; Žižková, Nikol (advisor)
This master thesis is focused on the binary and ternary systems with connective purposeful ettringite formation for fast hardening adhesive for ceramic tiles. It deals with the durability of these materials after exposure to the corrosive environment. It examines the physical and mechanical properties and mineralogy changes after exposure to corrosive environments. Within processing of this paper provides basic information concerning the connective concept of purposeful formation of ettringite.
Polymer-cement composites of increased refractoriness
Žůrová, Marcela ; Mončeková, Miroslava (referee) ; Šoukal, František (advisor)
The subject of the barchelor thesis is the preparation of high-strength polymer – cement composites based on the calcium aluminate cement and polyvinylalcohol. For macrodefect–free (MDF) composites are characterized by low porosity and the absence of microcracks. The main problem of the MDF composites is decreased resistance to water or moisture, with a decrease in strength. These compounds are interesting with its mechanical properties, which are greater than the strength of common materials (wood, glass, PMMA,…). Represent perspective type of material that could be used for construction purposes. The thermal degradation of the polymer, however, there are changes in the structure of the composite and to the deterioration of mechanical properties. This thesis is focused on characterization of the effect of temperature change on the structure, material composition and mechanical properties. The MDF composites were prepared based on calcium aluminate cement, which was gradually replaced by refractory additives. During the work was carried out tests of bending strength at various temperatures. Changes in the composition and structure were characterized by TG – DTA, XRD and SEM analysis.
Polymer-cement composites of increased refractoriness
Ryšková, Martina ; Opravil, Tomáš (referee) ; Šoukal, František (advisor)
The subject of the diploma thesis is the preparation of macro-defect-free (MDF) composites based on calcium-aluminate cement and organic polymer polyvinylalcohol. Attention focused on the optimization of the dose, the degree of hydrolysis and molecular weight of the polymer with respect to the heat resistance of the material. Thermal degradation of polyvinyl alcohol leads to changes in the structure of MDF composite. The study was mainly focused on the characteristics of polyvinyl alcohol dosage associated with the resultant mechanical properties of the material. During the work were monitored for changes in the mechanical properties of samples were cured at 60 °C and subsequently fired at 180 °C, 600 °C, 1000 °C and 1400 °C. It was tested in flexural strength, heat microscopy, TGA-DTA-EGA and SEM analysis.
Development of anorthite ceramics
Toman, Boris ; Šveda,, Mikuláš (referee) ; Sokolář, Radomír (advisor)
When firing calcium ceramic materials creates a new crystalline phase anorthite. It can significantly improve the properties of ceramic body. This work deals with the possibilities of development anortitové ceramics using non-plastic raw materials, particularly alumina cement compared with conventional ceramics based on mullite.
Study of volume changes of binders silicate
Nováček, Jaroslav ; Rovnaníková, Pavla (referee) ; Steuer,, Radek (referee) ; Pavlík,, Zbyšek (referee) ; Šťastník, Stanislav (advisor)
In theory, this work is devoted to the principles and methods of measurement of volume changes of mortars and concretes. Emphasis is placed on cement self-levelling screeds with initial shrinkage compensation. In the practical part of the work is devoted to the development of prototype measuring system designed for non-contact detection of volume changes hydrating silicate. Using the new measurement method is also practically examined the influence of boundary conditions on hydration volume changes of selected silicate binders, cement mortar and cement levelling compound based on four different connective concepts. In the calculation, this work focuses on the numerical modelling of volume changes of the examined compounds.
A study of the hydration of calcium aluminate cement in an excess of silica fume
Nehéz, Samuel Emil ; Švec, Jiří (referee) ; Novotný, Radoslav (advisor)
This thesis deals with the effect of silica fume (microsilica) on the hydration process of alumina cement (CAC). During the preparation of the samples, the effect of the amount of microsilica and the effect of the hydration temperature on the formation of hydration products were investigated. Microsilica was always in excess compared to alumina cement. The characterization of the raw materials was carried out using particle size measurement and calorimetry. In the case of the samples themselves, calorimetric measurements showed that the hydration process is divided into two separate events. Thanks to this, it was possible to stop the hydration at the desired time and examine the emerging hydration products. The presence of silica fume caused the formation of characteristic hydration products - strätlingite (C2ASH8). It was found that as the temperature of hydration increases, the resulting products form more quickly. Increased hydration temperature had a negative effect on mechanical properties. The properties and characterization of the prepared samples were further investigated using XRD, TG-DTA and scanning electron microscopy (SEM).

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