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Effect of alternative agents on controlled degradation of polypropylene
Kadlecová, Zuzana ; Figalla, Silvestr (referee) ; Bílek, Vlastimil (advisor)
This bachelor’s thesis focuses on the effect of degradation agents in controlled rheology polypropylene and its efficiency. That was evaluated on several types of polypropylene with different molecular weight, the strength of stabilization and content of degradation reagents (organic peroxide and nitroxide Irgatec® CR 76). Melt flow rate, rheometry, and molecular weight distribution methods were applied. Results of each method for unstabilized, stabilized polypropylene and polypropylene containing degradation agent were compared. It was determined, that higher polymer chain degradation efficiency is provided by organic peroxide, lower by nitroxide. The molecular weight distribution of polypropylene was much narrower with peroxide than with nitroxide even though it should have been conversely according to published data. The molecular weight distribution of polypropylene (Mw/Mn) was much narrower with nitroxide than with peroxide at all process temperatures.
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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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Rheology of Alkali-Activated Slag during Its Early Hydration Stages
Pazour, Miroslav ; Smilek, Jiří (referee) ; Bílek, Vlastimil (advisor)
This bachelor thesis focuses on the measurement of viscoelastic parameters of mixtures based on alkali-activated blast furnace slag during hydration. Hydration was monitored using isothermal calorimeter and initial and final setting time was determined for another comparsion by Vicat’s needle. These parameters were measured depending on activator dosage (water glass) and organic admixture dosage (hexylene glycol) and compared with each other. It was observed that storage modulus prevailed over loss modulus in fresh mixtures with lower dosage of activator, whereas in mixtures with higher dosage of activator viscous component began to prevail and complex modulus was rather descreasing. Conversely, in mixtures with higher hexylene glycol dosage complex modulus was significantly increasing. Evolution of modules in time correlated with calorimetric curves and setting times. During setting time, which is assigned to formation of primary C-A-S-H, values of viscoelastic parameters was remarkably increasing.
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Effect of cement by-pass dust on properties alkali-activated slag
Janíčková, Vlasta ; Kalina, Lukáš (referee) ; Bílek, Vlastimil (advisor)
This masters thesis deals with influence of cement bypass kiln dust on physico-mechanical properties of alkali activated slag and influence of chosen compounds of cement bypass kiln dust on alkali activated slag. Using alkali activated slag is limited by its shrinkage. The setting time with different amount of cement bypass kiln dust and its chosen compounds (CaO, KCl and K2SO4) were measured by isotermal and isoperibolic calorimetry too. The strength and length changes of the mixtures with different amount of cement bypass kiln dust were measured. Samples were analysed by X-Ray diffraction analysis and scanning electron microscopy. It has been found that the increasing addition of dust reduce setting time, flexural and compresive strength and shrinkage. Presence of free CaO was found being one of the reasons for accelerated setting. KCl and K2SO4 have retarding effect but influece of free CaO prevails even for its lower contents. Long-term properties evolution is strongly dependent on curing regime due to potential volume expansion.
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Possibilities of Chloride Ions Binding in Alkali-Activated Slag Systems
Chadima, Jan ; Kalina, Lukáš (referee) ; Bílek, Vlastimil (advisor)
This bachelor thesis deals with chloride binding in alkali activated slag and tries to bind chlorides by adding metakaolin, alumina and cement bypass kiln dust to form Friedel’s salt in alkali activated system. These admixtures were selected as a potential sources of aluminate ions that are necessary for the formation of this salt. The amount of chlorides in solid samples and in leachates was determined by Volhard titration. To find out phase composition X-ray diffraction and thermogravimetric and differential thermal analysis were used. Chloride ions were bound in by far the greatest extent in the pastes containing cement bypass dust because only in this case Friedel’s salt was formed. In the case of alumina and metakaolin chlorides were bound likely via adsorption on C-S-H phase.
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Possibilities of the utilization of the waste sand from the water glass production in building industry
Bílek, Vlastimil ; Kalina, Lukáš (referee) ; Opravil, Tomáš (advisor)
Nowadays, the waste sands from the water glass production have no utilization and due to high alkali content are considered as a dangerous waste. So the aim of this thesis is to find and study some possibilities of their utilization in the building industry. First of all, some necessary analysis of these sands were performed and then some advantages and disadvantages of their application for production of materials based on portland cement and alkali activated materials were studied. Characteristics of fresh and hardened pastes, mortars and concretes containing these waste sands were determined. The most tested properties were their workability and their compressive and flexural strength. Close attention for the risks of alkali-silica reaction and for options of its suppressing by the mineral admixtures was paid.
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Validation of an innovative approach to the design of alkali-activated materials
Kejík, Marek ; Kucharczyková, Barbara (referee) ; Bílek, Vlastimil (advisor)
This thesis presents an approach to express the composition of alkali-activated materials based on three main characteristics. These are the type of activator, the molarity of the activator, and the volume fraction of the precursor or aggregate. The aim of this work is to provide a practical verification of this approach, in particular with respect to the amount of precursor, aggregates, and activator at a constant molarity of the three basic activator types (Na2CO3, NaOH, sodium water glass). The effects of these factors on their basic properties, namely workability, shrinkage, and mechanical properties, were studied for the prepared samples of pastes and mortars based on alkali-activated slag. These results were further supported by mercury intrusion porosimetry and electron microscopy. The results obtained confirmed the assumed key influence of the volumetric representation of the precursor, aggregates, and activator on the absolute values of the studied properties as well as on their relative changes. These were very different for the different activators, which is mainly due to the different abilities of the hydration products formed to fill the space between the slag and aggregate grains. The result of this work is a summary of the knowledge about the properties of alkali-activated materials over a given range of compositions, anchored by a universal approach for the design of the composition of these materials, which can be used in further research in this field.
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Possibilities of classical fly ash utilization after denitrification of flue gas
Snop, Roman ; Dvořák, Karel (referee) ; Bílek, Vlastimil (referee) ; Havlica, Jaromír (advisor)
This doctoral thesis, "Possibilities of using conventional fly ash after flue gas denitrification", deals with the solution and processing of data on the issue of ammonia / contaminated fly ash after selective non-catalytic reduction (SNCR) technology in coal-fired power plants. Also this thesis is focused on experimental verification of the effect of ammonium salts on the properties of fly ash and the effect on the working environment. Basic data on the issue of ammonia ash were collected. Specifically, these are several main areas of research. The binding of ammonia in fly ash produced after SNCR is described, the problem of determination of ammonium ions in fly ash, mortars and concretes is solved. Furthermore, the effects of the use of ammonia fly ash on the properties of concrete are experimentally verified, and the work also deals with the leachability of ammonia fly ash
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Modification of the properties of alkali activated materials by polymer admixtures
Mikhailova, Olesia ; Bílek, Vlastimil (referee) ; Vejmelková,, Eva (referee) ; Žižková, Nikol (referee) ; Rovnaník, Pavel (advisor)
V současné době se v betonářském průmyslu ve velké míře používá portlandský cement (PC), jehož výroba má značný dopad na životní prostředí a zároveň se jedná o neudržitelný proces. Snahy o ekologičtější stavebnictví zahrnují využití několika aluminosilikátů, které mohou být buď odpadními produkty získanými z jiných průmyslových výrob, jako je granulovaná vysokopecní struska, popílek a křemičitá dýmka, nebo materiály pocházející z energeticky méně náročných průmyslových procesů, jako je metakaolin. Použití těchto materiálů při výrobě stavebních materiálů rovněž přispívá ke snížení výrobních nákladů. Aktivace aluminosilikátových materiálů alkalickými aktivátory vede k získání vysoce pevných materiálů, které lze považovat za alternativu běžného PC. Navzdory mnoha výhodám alkalicky aktivovaných aluminosilikátů (AAA) existuje zásadní nevýhoda, která se týká výrazného autogenního smršťování a smršťování při vysoušení, k němuž může docházet během tuhnutí materiálu. Tento jev vede k mikrotrhlinám a zhoršení mechanických lomových vlastností. Polymerní příměsi mohou modifikovat vlastnosti čerstvého a vytvrzeného materiálu AAA a překonat výše uvedené problémy. Tato disertační práce se zabývá vlivem polymerních přísad v různých hmotnostních množstvích aluminosilikátového pojiva na snižování smrštění a křehkosti a na zvýšení lomové houževnatosti. Jako polymerní příměsi byly vybrány polyetylen glykol (PEG), polypropylen glykol (PPG) a různé typy komerčních polymerů z řady dispergovatelných polymerních prášků Vinnapas®. Jejich vliv na vlastnosti získaných materiálů byl porovnáván s vlivem práškového přípravku proti smrštění Peramin SRA 40. Vzorky byly testovány na pevnost v ohybu a tlaku a jejich mikrostruktura byla zkoumána pomocí rtuťové porozimetrie a skenovací elektronové mikroskopie. Jedna z kapitol práce se zabývá studiem různých charakterizačních technik vzniku hlavních reakčních produktů v alkalicky aktivované strusce, jako jsou RTG difrakční analýza, Fourierovou tran
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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.
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