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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.
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Combined Effect of Li, Cu and S Doping on Structure and Hydration of β Dicalcium Silicate
Sedlačík, Martin ; Bartoníčková, Eva ; Novotný, Radoslav ; Palovčík, Jakub ; Másilko, Jiří ; Staněk, Theodor ; Rybová, Alexandra
This study investigates the effect of Li, Cu and S on the structure and hydration of the beta modification of dicalcium silicate (β-C₂S). The doped β-C2S phase was prepared by burning beta-C2S with dopant sources. The structure of prepared β-C2S samples was examined using X-ray diffraction, scanning electron microscopy and infrared spectroscopy. Heat evolution during hydration was assessed by isothermal calorimetry. A positive effect on cement hydration was observed for several dopant combinations.
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Harmonized FMEA analysis
Riabov, Mikhail ; Szendiuch, Ivan (referee) ; Novotný, Radovan (advisor)
The target of the diploma thesis on „Harmonized FMEA analysis“ is to familiarize with principles of quality planning and studying the theory of existing APQP tools. Another goal is to learn the basics of the new manual of harmonized FMEA analysis and discover some available SW tools for project support. This diploma thesis will be focused mainly on DFMEA analysis of traction assembly and the concept of changing to new harmonized version from VDA/AIAG will be explained. This concept meets the requirements for clear and comprehensible output required by the manufacturer, supplier, and customer. The diploma thesis is elaborated as a detailed clear guide for easier processing of FMEA according to the new manual.
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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.
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Heat insulating moulded refractory materials
Novotný, Radoslav ; Lang, Karel (referee) ; Raschman,, Pavel (referee) ; Havlica, Jaromír (advisor)
Doctoral thesis is focused on the study, research and development of heat insulating moulded refractory materials. The replacement of shaped instead of unshaped refractories is recently and strongly industrially demanded and belongs to ongoing research topics. With the increasing demand of energy savings, the excellent insulation properties are essential. The insulating properties of castables are the result of targeted porosity formation. The porosity is coming from the controlled air intrusion into material resulted to foamed structure. The foaming process was achieved by mixing of separately prepared aqueous foam into raw castable slurry or by in situ foaming of intensively mixed castable slurry with the surfactant additive. Nevertheless, the study of foam behaviour and the influence of additives on binder hydration and setting processes (i.e. calciumaluminate cement) was substantial for successful preparation of the experimental samples. The two types of the experimental samples were prepared. The first one was based on mixing of kaolin slurry with pre-prepared aqueous foam, whereas the de-aglomeration ability of kaolin specie was utilized to water-particle film formation. In situ foaming of multicomponent system is the second one. The both processes brought some negative attributes, so the optimal properties of prepared castables were achieved by their combination.
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Customer complaints from quality point of view
Voborník, Petr ; Hégr, Ondřej (referee) ; Novotný, Radovan (advisor)
This work deals with issues of customer complaints management from quality point of view. The general aim is to introduce complaints management process and complaints evaluation. It introduces key monitored parameters of complaint management process. There is introduced complexity of complaints management process. Design of database system IS. Reporting of complaints.
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Influence of fumed silica on the properties of ultra-high performace cement composite
Hrbáčová, Markéta ; Švec, Jiří (referee) ; Novotný, Radoslav (advisor)
This diploma thesis deals with the properties of concrete based on reactive powdered materials. Pyrogenic nanosilica (Aerosil 200, Aerosil 380) was added to the concrete in various volume ratios. The aim was to design and prepare a series of samples in order to determine their basic properties, and to determine the behavior of selected samples during penetration by a high-speed projectile compared to the reference sample. In order to determine the strength of the samples, compression and tensile bending tests were performed. The so-called multihit test was used to determine ballistic resistance. The differential effect factor was also determined experimentally and compared with the reference sample. An electron microscope was used to monitor the behavior of the fibers in the binder as well as the binder itself. Hydration curves for individual samples were generated using calorimetric measurements. The bulk density of the samples and the spills during their preparation were also monitored. The resulting strength of the nanosilica samples did not show higher values compared to the reference sample. The results of the multihit test did not show considerable changes compared to the reference composite.
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Applications of wavelet transform in Mathematica and Sage
Novotný, Radek ; Trzos, Michal (referee) ; Rajmic, Pavel (advisor)
This thesis focuses on image processing using wavelet transform. The usage of wavelet transform is analysed especially for image compression and image noise reduction purposes. The analysis describes in detail aspects and application of the following wavelet transform methods: CWT, DWT, DTWT, 2D DWT. The thesis further explains the meaning of the mother wavelet and studies certain specific kinds of wavelets, kinds of thresholding and its purposes and also touches on the JPEG2000 standard. Mathematica and Sage software packages were used to design algorithms for image compression and image noise reduction, utilising relevant wavelet transform findings. The concluding part of the thesis compares the two software packages and results obtained using different algorithms.
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