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Calcium aluminates - hydration under various initial conditions
Tomala, Libor ; Másilko, Jiří (referee) ; Koplík, Jan (advisor)
This thesis deals with the preparation of calcium aluminate phases, namely monocalcium aluminate (CA), monocalcium dialuminate (CA2) and dodecalcium heptaaluminate (C12A7) and their hydration at temperatures of 20, 30 and 60 ° C. Preparation was carried out by sintering aluminium oxide and calcium carbonate in the correct molar ratio at a temperature typical for each of the phase preparation (1450, 1600 respectively 1360 ° C) in superkanthal furnace. Firings were conducted repeatedly until reaching the sufficient purity, which was determined by X-ray diffraction analysis on the diffractometer Empyrean from the PANalytical company. The pure calcium aluminate phases were subsequently hydrated in the already mentioned temperatures and progress was monitored on TAM Air isothermal calorimeter made by TA Instruments. The resulting hydrated products were identified again by using XRD.
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Meta-talc Application in Inorganic Materials
Bednárek, Jan ; Rovnaník, Pavel (referee) ; Palou, Martin (referee) ; Havlica, Jaromír (advisor)
This thesis is focused at possibilities of preparation and characterization of XRD-amorphous delaminated and dehydroxylated talc phase – meta-talc, which can have its potential application and a starter material for a preparation of magnesium-silicate analogues of geopolymers. Changes in structure and morphology of talc ore were observed during this work. For the purposes of this research, two various talc ores – chloritic and dolomitic were examined. Whole process of meta-talc preparation was examined with whole scale of instrumental techniques such as X-ray diffraction, simultaneous thermogravimetric a differential thermal analysis, infrared spectroscopy, scanning electron microscopy or laser analysis of particle size. Meta-talc can be obtained via mechanochemical activation of talc ore with subsequent calcination. Mechanochemical treatment lead to destruction of original crystal structure and breaking of original bonds, i.e. the product of this treatment was almost amorphous and delaminated. Most of hydroxyl groups were converted to molecules of water which remained adsorbed or coordinated in ore structure. These molecules were removed during calcination step.
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The study of sulfate depletion in cement binders
Jurko, Michal ; Švec, Jiří (referee) ; Novotný, Radoslav (advisor)
This bachelor thesis deals with the study of sulfate depletion in cement binders. Basic knowledge about cement binders is summarised at the beginning of the theoretical part. The theoretical part goes on to describe the hydration of Portland cement (PC) and to briefly describe the influence of different types of milling on PC particle size. In the experimental part, PC fractions of various average particle sizes were prepared on a planetary ball mill for wet conditions. On the prepared cement, their hydration was studied using isothermal calorimetry; especially sulfate depletion, portlandite precipitation, heat flow rate and induction period interval. n the thesis were also used analyzes for autogenous shrinkage, XRD and STA. The input raw materials are cement CEM I 42,5 R (grey, Českomoravský cement, a.s. – Mokrá, Czech Republic) and sulfate-resistant cement CEM I 52,5 R (white, Aalborg Portland, a.s. – Aalborg, Denmark). On the basis of the results analysis, a proposal was made to correct the presence of sulfate ions by adding gypsum in these cements. In the case of CEM I 52,5 R the correction is recommended and in the case of CEM I 42,5 R the correction is necessary.
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Influencing the hydration of high-performance composites using zinc ions
Všetečka, Tomáš ; Hajzler, Jan (referee) ; Novotný, Radoslav (advisor)
The bachelor thesis is focused on the influence of hydration of high-performance cementitious composites, more specifically reactive powder composites. Zinc ions were supplied by the compounds of zinc oxide and zinc sulphate heptahydrate. Zinc ions were added by weight content to cement at concentrations of 0.2; 0.5 and 1.0 wt. %. The development of properties depending on the content of zinc ions and the type of compound used was monitored in this work. The measured values were compared with reference values that did not contain zinc ions. The highest compressive strengths were obtained with a sample containing 1.0% Zn in the form of zinc oxide. However, this sample is associated with a longer setting time due to the retarding effect of zinc ions on hydration. The retardation effect was monitored using isothermal calorimetry. For samples containing zinc ions, a negative effect on the brass layer of steel fibers, which was used as reinforcement, was observed. Due to the addition of zinc ions, dezincification and subsequent removal of brass from the surface of the fibers took place. Therefore, these specimens had lower tensile strengths. A positive effect on the differential ballistic protection efficiency factor was observed for a sample containing 1% Zn in the form of zinc oxide.
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Influence of calcium sulphate type on hydration of Portland cement
Šimčíková, Ivana ; Šiler, Pavel (referee) ; Šoukal, František (advisor)
My bachelor thesis deals with the study of the influence of calcium sulphate types on the hydration of Portland cement. Hydration is performed at 15 °C, 25 °C and 40 °C. In the theoretical part we find a description of the hydration of Portland cement and the influence of the type and amount of gypsum on the hydration period. The experimental part contains the preparation of samples for measurement and the principle of calorimetry including a description of the calorimetric curve. The data obtained from the calorimetric curve was processed into ternary diagrams for illustration. The diagrams show that the more calcium sulphate is soluble, the shorter the induction period, the times of reaching the minimum heat flow and heat flow at the maximum silicate peak will have. Further, the diagrams showed that as the amount of water in sulphate increases, so does the amount of hydration heat released.
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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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The study of zinc influence on Portland cement hydration.
Ptáček, Martin ; Janča, Martin (referee) ; Šiler, Pavel (advisor)
The topic of this work is the monitoring of the effect of zinc on the hydration process in Portland mixed cement (specifically with the addition of finely ground granulated blast-furnace slag, high temperature fly ash and fluidized bed combustion filter ash). How much zinc and at what time it remains in the pore solution during hydration. Activation energy of a mixture of cement with zinc in the form of soluble salts (Zn(NO3)2.6H2O and ZnCl2) and insoluble oxide (ZnO) by isothermal calorimetry was also investigated. The XRF method has shown composition during hydration. The zinc retardation effect was investigated by isothermal calorimetry and activation energy was calculated using this method. The XRF and ICP-OES methods were used to measure the zinc content of the pore solution. And the amount of portlandite was monitored by the DTA and XRF method.
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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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Influencing the hydration of high-performance composites using zinc ions
Všetečka, Tomáš ; Hajzler, Jan (referee) ; Novotný, Radoslav (advisor)
The bachelor thesis is focused on the influence of hydration of high-performance cementitious composites, more specifically reactive powder composites. Zinc ions were supplied by the compounds of zinc oxide and zinc sulphate heptahydrate. Zinc ions were added by weight content to cement at concentrations of 0.2; 0.5 and 1.0 wt. %. The development of properties depending on the content of zinc ions and the type of compound used was monitored in this work. The measured values were compared with reference values that did not contain zinc ions. The highest compressive strengths were obtained with a sample containing 1.0% Zn in the form of zinc oxide. However, this sample is associated with a longer setting time due to the retarding effect of zinc ions on hydration. The retardation effect was monitored using isothermal calorimetry. For samples containing zinc ions, a negative effect on the brass layer of steel fibers, which was used as reinforcement, was observed. Due to the addition of zinc ions, dezincification and subsequent removal of brass from the surface of the fibers took place. Therefore, these specimens had lower tensile strengths. A positive effect on the differential ballistic protection efficiency factor was observed for a sample containing 1% Zn in the form of zinc oxide.
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Influence of calcium sulphate type on hydration of Portland cement
Šimčíková, Ivana ; Šiler, Pavel (referee) ; Šoukal, František (advisor)
My bachelor thesis deals with the study of the influence of calcium sulphate types on the hydration of Portland cement. Hydration is performed at 15 °C, 25 °C and 40 °C. In the theoretical part we find a description of the hydration of Portland cement and the influence of the type and amount of gypsum on the hydration period. The experimental part contains the preparation of samples for measurement and the principle of calorimetry including a description of the calorimetric curve. The data obtained from the calorimetric curve was processed into ternary diagrams for illustration. The diagrams show that the more calcium sulphate is soluble, the shorter the induction period, the times of reaching the minimum heat flow and heat flow at the maximum silicate peak will have. Further, the diagrams showed that as the amount of water in sulphate increases, so does the amount of hydration heat released.
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