National Repository of Grey Literature 149 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Influencing the pozzolanic reaction of silica fume in a high-performance cementitious composite
Všetečka, Tomáš ; Šoukal, František (referee) ; Novotný, Radoslav (advisor)
This work deals with the effect of cement hydration and pozzolanic reaction of a high-perfomrance cement composite containing Portland cement and silica fume as binder. Concentrations of 0,5; 1,0; 2,0 and 4,0 wt.% of calcium ions to the binder were chosen to observe the effect. The selected compounds were calcium oxide (CaO), calcium hydroxide (Ca(OH)2), calcium formate (CF), calcium nitrate tetrahydrate (CN) and calcium chloride (CC). Calorimetric measurements showed that the optimum water to binder ratio was 0.4. Due to the lower workability, no high-performance cement composites were prepared but only pastes of high-performance cement composite. The effect of the added compounds on the silica fume-containing system was evaluated by isothermal calorimetry, with only samples containing CaO or Ca(OH)2 showing a measurable response. The effect of the added compounds on the silica fume containing system was evaluated by isothermal calorimetry. Subsequently, the effect of 4,0 wt.% Ca2+ in the CF, CN and CC forms on the system containing silica fume and 1,0 wt.% Ca2+ in the CaO or Ca(OH)2 form was evaluated using the R3 test. Isothermal calorimetry was also applied to paste samples containing cement and silica fume as a binder system, where a significant effect on the length of the induction period, on the value of the minimum heat flux in the induction period and on the value of the maximum heat flux in the main hydration peak was observed, especially for the compounds CF, CN and CC. The flexural tensile and compressive strengths of the paste samples were determined at 1, 3, 7 and 28 days after the start of hydration. The highest influence on the three-point bending tensile strength was again observed for compounds CF, CN and CC, with samples reaching significantly lower values than the reference (this was probably due to insufficient dissolution of the compounds). A lower influence on the flexural tensile strengths was observed for the oxide and calcium hydroxide samples. In the case of compressive strengths, there was a significant increase for CF, CN and CC compounds at 0,5 wt.% and 1,0 wt.% Ca2+ concentrations. In the thermal analysis and diffractometry results, a trend of loss of portlandite at the expense of CSH gel was observed for samples containing 4,0 wt.% Ca2+ in compounds CF, CN and CC. Thus, the added compounds probably influenced the kinetics of cement hydration so much that the silica fume had more time for pozzolanic reaction.
Role of superplastisizers in alkali activated aluminate silicate mixtures
Habrdová, Eva ; Šoukal, František (referee) ; Havlica, Jaromír (advisor)
Preparation of geopolymers with main components of slug and metakaolin. After being alcali activated the raw materials are complemented by superplasticizers of different kind and concentracion.
Application of fly ashes from fluid bed coal combustion within refractory materials
Kotrla, Jan ; Bartoníčková, Eva (referee) ; Šoukal, František (advisor)
The thesis deals with the possibility of utilization of fluid ash in refractory materials and its influence on resulting properties. This work studies the effect of bed and filter ash addition on properties of the droplet and resulting mechanical properties, bulk density, shrinkage and firing temperature of stove fireclay. The subject of this thesis is also reduction of SO2 emissions evolved burning of fireclay containing fluid ash rich of anhydrite. Emissions of SO2 were observed by TG-TDA-EGA method. Characterization of prepared samples and study of heat treatment processes was based on XRD, TG-DTA-EGA, TDA, SEM–EDS, heating microscope and isothermal calorimetry.
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.
Reactivity and controll of properties of metallic materials
Tkacz, Jakub ; Šoukal, František (referee) ; Zmrzlý, Martin (advisor)
This thesis is focused on corrosion protection of magnesium alloys AZ 91. Very important is material corrosion in some environments and last but not least surface treatment as grinding, polishing and etching. Theoretical part of this thesis is about magnesium and magnesium alloy. It focuses on properties, in order to determine the best procedure for corrosion protection. It characterize material corrosion- for example corrosion in special environment (atmosphere, water, etc.) or elektrolyte corrosion. Big part of theoretical part is focused on electrochemistry, in particular kinetic aspects (Tafel diagrams, corrosion current, etc.) and potentiostatic testing, where are observed properties of material in relation to potential: corrosion potential Ecorr, brakedown potential Ebd and repassivation potential Erp. This work present preparing, utilization and positive or negative aspects of corrosion protection. Metallography is important too since metallographical preparation is crucial for the research on the material. Described metallography procedures are mounting, grinding, polishing, etching and interpretation. Experimental part of this thesis is in particular about corrosion properties of magnesium alloy AZ 91. It focuses on calculation of corrosion rate in defferent environments. Principle is mass defekt of the alloy. The environments are: destilled water, hot service water and 3% NaCl solution (like sea water). Last but not least are important. procedure manipulation with materials. Very important are choice and composition of solutions, etching time, choice of polishing cloth, lubricant solution and good pressure. Beacuse of this aspects can be show corrosion action of environments on magnesium alloy AZ 91 by photographies.
Preparation of hystorical geopolymers
Šrámková, Eva ; Šoukal, František (referee) ; Havlica, Jaromír (advisor)
Diploma thesis studies historical bonding agents on the base of geopolymers. The aim of the thesis is to find a proper material composition, especially made of natural clay materials (kaolinite, bentinite) and their modifications (metakaoline). These bonding agents have to have a suitable type of an activator that guarantees good bonding properties. Therefore testing of various kinds of alkaline activating ingredients on the same mineral composition was done. Except of usual hydroxides and a water glass, ancient natrons (mixtures of alkaline carbonate with addition of appropriate chlorides) and a lime mash were used as the activators. From the above mentioned mixtures, series of samples (columns 20 x 20 x 100 mm) stored at the laboratory temperature were prepared. In the prepared mashes, their workableness and moulding were investigated. In the developed samples, their surface appearance was observed together with a number of efflorescence and its types. An indivisible part of the research was formed by determination of mechanical properties of the experimental columns such as a compressive strength and a tensile strength in bending. Furthermore, phase composition of the samples and its changes with a temperature increase were investigated. For these tests, XRD and TG – DTA methods were used. A multi-seat isoperbolic calorimeter was used to study hydratation that was also the important part of the general evaluation of designed mixtures.
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.
Preparation of MDF composites of increased moisture resistance
Žůrová, Marcela ; Šiler, Pavel (referee) ; Šoukal, František (advisor)
The subject of the thesis is to improve the moisture resistance of MDF (macro-defect-free) composites prepared on the basis of aluminous cement and polyvinyl alcohol. These materials are characterized by the absence of defects in the structure and high mechanical performance. These features make MDF composites a promising type of material that could be used in the future for construction purposes. The basic deficiency of MDF composites is insufficient resistance to water or moisture, accompanied by a significant decrease in strength. Therefore, this work deals with increasing of moisture resistance using organotitanate agent and modification of the polymer. Two types of polyvinyl alcohols differing in hydrolysis degree and degree of the polymerization has been modified. Based on the results of the measurement the effect of storage conditions on the properties and structure of prepared MDF composites was observed. The characterization of MDF composites were realized by measurement of flexural strength in bending, scanning electron microscopy with EDS analysis, TG-DTA-EGA, water absorption and consequently the porosity of all prepared MDF composites.
Recyclation of dust from production of dry mortar blends
Ondrůšková, Nela ; Novotný, Radoslav (referee) ; Šoukal, František (advisor)
The work deals with the problem of disposal of ever-increasing waste (dust) from the production of building materials and examines the possibility of recycling dust dust into cement repair mortar. The aim of this work was to determine the composition of individual dust particles from the production of cement mixtures and to determine their mechanical properties, as well as to determine the ideal ratio of dust particles to each other when mixing the dust mixture and its mechanical properties. This mixture consisted mainly of dust from products based on Portland cement, aluminous cement, gypsum and lime hydrate. The mixture further replaced part of the cementitious mortar and the impact of the additive on the mechanical properties of the cementitious mortar was determined. X-ray fluorescence spectrometry was used to determine the elemental composition, and X-ray diffraction analysis was used to determine the mineralogical composition. Test specimens were prepared according to the ČSN EN 12390 standard. Mechanical strength tests were performed on the test specimens. A large part of the test specimens could not be subjected to mechanical tests because the test specimen did not solidify even after a long time. The individual measurements that could be made show that the mechanical properties of the dust samples show values which have shown that the dust cannot be recycled into the product due to its instability. Dust particles have too diverse composition and in combination with cementitious repair mortar do not have the required properties. The problem is especially the sampling from the data, which did not solidify at all and thus excluded the remaining samples with already good properties of the same sample. When designing the method of recycling, it was necessary to take into account which product of the company is most in demand, where recycling would also make economic sense, which is also an important indicator for the operation of the company today. Dust particles could prove successful in another product, but it would not be advantageous for the company now, so now the recycling of dust particles will not start and they will be further disposed of in the same way.
Durability of alkali-activated systems
Šafář, Martin ; Šoukal, František (referee) ; Kalina, Lukáš (advisor)
Alkali activated binders have the potential to become an alternative construction material to ordinary portland cement binders. This thesis concentrates on durability testing of alkali activated blast furnace slag and fly ash based concrete. The chosen aspects of durability included sulfate resistance, acid resistance, carbonation, freeze-thaw resistance, frost-salt resistance and porosity. Microstructural changes and formation of new crystalline phases were observed using XRD and SEM-EDX analysis. Potential application of the tested material from the durability point of view was evaluated by comparison with a reference ordinary portland cement based concrete.

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