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Time evolution of rheological parameters of slag activated with various activators
Pazour, Miroslav ; Smilek, Jiří (referee) ; Bílek, Vlastimil (advisor)
Tato diplomová práce se zabývá aktuálními poznatky, společně s optimalizací oscilačních měření pomocí hybridního reometru, ale hlavně pozorováním změn reologických parametrů v čase past mleté granulované vysokopecní strusky aktivované různými aktivačními roztoky s koncentrací alkálií M: 4 and 7.5 moldm. Výsledky byly pro diskuzi podpořeny výstupy z Vicatovy metody a izotermické kalorimetrie. Nejprve bylo zjištěno, že limit lineární viskoelastické oblasti se zmenšuje v čase. Dále bylo pozorováno, že v time sweep testech vykazovala struska aktivovaná křemičitany nejnižší hodnoty komplexního modulu a struska aktivovaná hydroxidy o koncentraci 4 moldm nejvyšší hodnoty a ostatní pasty vykazovaly hodnoty mezi těmito dvěma extrémy a měly mezi sebou porovnatelné hodnoty. Podobný trend byl pozorován u vývoje kritické meze oscilačního napětí, získaného z amplitude sweep testů (přerušovaně a nepřerušovaně). Oba výše zmíněné parametry, komplexní modul a mez napětí, se vyvíjely v čase. Výsledky všech testů jasně ukázaly, že povrchová chemie hraje roli ve výsledném reologickém chování. Odsud, povaha a koncentrace aktivátoru ovlivňují reologické vlastnosti skrze efekty Na a K iontů, stejně tak skrze koncentraci, která má dopad na elektickou dvojnou vrstvu. Reologické chování může být také ovlivněno dalšími faktory, např. viskozitou aktivačního roztoku a celkovou kinetikou hydratačního procesu.
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Composite medical textile - preparation, characterization, application
Bušinová, Zuzana ; Ing. Vítězslav Zilvar. (referee) ; Krouská, Jitka (advisor)
This bachelor thesis deals with the setting time of the Safix plus gypsum bandage from the Hartmann - Rico a.s. company. The aim of the work is to improve the quality control process of this product and developing a simple robust method for determining the quality control of the Safix plus plaster cast. Two methods and instruments were chosen for the measurement, the Vicat instrument and a rheometer. Vicat's device works on the principle of measuring the depth of penetration of the penetrating body into the sample from a constant height. A rheometer is used to measure rheological properties of the sample, such as viscosity. For both of these methods, it was necessary to prepare the gypsum powder from the gauze. By measuring on the rheometer, the setting time was determined to be 2.4 ± 0.1 minutes and by measuring on the Vicat instrument the observable setting time was determined to be 3.1 ± 0.2 minutes and the complete solidification time to be 6.0 ± 0.4 minutes. Due to the purchase price of the rheometer and in combination with the intended purpose (i.e., product quality control in the commercial sector), the use of a Vicat device appears to be a more suitable option, not only due to the considerably lower purchase price, but also due to simplicity of measurement.
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Influence of exothermic sleaves on solidification of aluminium alloys
Zajíček, Roman ; Krutiš, Vladimír (referee) ; Roučka, Jaromír (advisor)
The master’s thesis deals with the influence of the exothermic risers on the solidification of aluminum alloys. The work is divided into three parts. The first theoretical part describes the differences of properties of cast aluminum alloys compared to other based metals, especially iron alloys. It also describes the methodology of designing risers, composition of exothermic mixtures and finally gives an overview on the simulation programs on the market, their application in foundry practice and briefly explains how to define the material in the simulation program ProCAST. The second part describes the experimental measurement of the solidification time of aluminum alloy AlSi7Mg0,3 in the sand form with exothermic riser. The final section describes the simulation of experimental measurements. Further with help of simulation software it is tried to find the general principles that have an influence on feed module rate of exothermic riser.
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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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Structure and properties of high silicon ductile iron
Paták, Daniel ; Kaňa, Václav (referee) ; Záděra, Antonín (advisor)
The diploma thesis was focused on the production of solid solution strengthened ductile iron. In the first part, research dealing with nucleation embryos and nucleation mechanisms of graphite was developed. Furthermore, the mechanical properties of high silicon ductile irons, their tendency to form chunky graphite and its effect on mechanical properties were described. In the experimental part, 3 melts with 4; 4.5 and 4.1% Si content were cast. Tensile tests, metallographic samples and numerical simulations were performed to compare the mechanical properties, microstructure and chunky graphite appearance as a function of solidification time and silicon content.
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Time evolution of rheological parameters of slag activated with various activators
Pazour, Miroslav ; Smilek, Jiří (referee) ; Bílek, Vlastimil (advisor)
Tato diplomová práce se zabývá aktuálními poznatky, společně s optimalizací oscilačních měření pomocí hybridního reometru, ale hlavně pozorováním změn reologických parametrů v čase past mleté granulované vysokopecní strusky aktivované různými aktivačními roztoky s koncentrací alkálií M: 4 and 7.5 moldm. Výsledky byly pro diskuzi podpořeny výstupy z Vicatovy metody a izotermické kalorimetrie. Nejprve bylo zjištěno, že limit lineární viskoelastické oblasti se zmenšuje v čase. Dále bylo pozorováno, že v time sweep testech vykazovala struska aktivovaná křemičitany nejnižší hodnoty komplexního modulu a struska aktivovaná hydroxidy o koncentraci 4 moldm nejvyšší hodnoty a ostatní pasty vykazovaly hodnoty mezi těmito dvěma extrémy a měly mezi sebou porovnatelné hodnoty. Podobný trend byl pozorován u vývoje kritické meze oscilačního napětí, získaného z amplitude sweep testů (přerušovaně a nepřerušovaně). Oba výše zmíněné parametry, komplexní modul a mez napětí, se vyvíjely v čase. Výsledky všech testů jasně ukázaly, že povrchová chemie hraje roli ve výsledném reologickém chování. Odsud, povaha a koncentrace aktivátoru ovlivňují reologické vlastnosti skrze efekty Na a K iontů, stejně tak skrze koncentraci, která má dopad na elektickou dvojnou vrstvu. Reologické chování může být také ovlivněno dalšími faktory, např. viskozitou aktivačního roztoku a celkovou kinetikou hydratačního procesu.
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Composite medical textile - preparation, characterization, application
Bušinová, Zuzana ; Ing. Vítězslav Zilvar. (referee) ; Krouská, Jitka (advisor)
This bachelor thesis deals with the setting time of the Safix plus gypsum bandage from the Hartmann - Rico a.s. company. The aim of the work is to improve the quality control process of this product and developing a simple robust method for determining the quality control of the Safix plus plaster cast. Two methods and instruments were chosen for the measurement, the Vicat instrument and a rheometer. Vicat's device works on the principle of measuring the depth of penetration of the penetrating body into the sample from a constant height. A rheometer is used to measure rheological properties of the sample, such as viscosity. For both of these methods, it was necessary to prepare the gypsum powder from the gauze. By measuring on the rheometer, the setting time was determined to be 2.4 ± 0.1 minutes and by measuring on the Vicat instrument the observable setting time was determined to be 3.1 ± 0.2 minutes and the complete solidification time to be 6.0 ± 0.4 minutes. Due to the purchase price of the rheometer and in combination with the intended purpose (i.e., product quality control in the commercial sector), the use of a Vicat device appears to be a more suitable option, not only due to the considerably lower purchase price, but also due to simplicity of measurement.
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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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|
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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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