National Repository of Grey Literature 44 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Optimization of the hardening and drying process of non-cement refractory castables based on colloidal SiO2
Zbíral, Roman ; Koplík, Jan (referee) ; Švec, Jiří (advisor)
Thesis deals with drying and its effect on refractory materials based on materials with zero cement content. Heat-resistant materials prepared by the sol-gel method, i.e., a process where the input raw materials are first formed into a colloidal solution, in our case already prepared by the manufacturer, and then a gel is formed with gelation reagent. This sol must be poured into a mold before gelation processes start and gel mesh formation occur. These materials can have better mechanical properties and better firing possibilities than standard cement materials, and a shorter preparation time. These refractory materials will be examined from the point of view of drying result gel, but also with the effect of subsequent firing and mechanical properties. Samples of sol, aluminate cement, model and real mixture will be analyzed using thermal methods (DSC, TG, DTA and thermal microscope). XRD technique was used to determine content of crystalline phases.
Study of an alternative binder based on the carbonation of ladle funace slag
Mikulová, Mária ; Koplík, Jan (referee) ; Másilko, Jiří (advisor)
This master’s thesis is focused on the investigation of the chemical processes during the carbonation of a ladle furnace slag (LFSU) and on the investigation of the long-term development of the composition and selected properties of carbonated compacts of LFSU. The main mineralogical phases of the LFSU, -dicalcium silicate (-C2S) and -dicalcium silicate (-C2S), were synthetised for the study. The carbonation reactivity of these phases was examined by perfusion calorimetry. A significantly higher reactivity with CO2 for -C2S was observed. The development of compressive strength, changes in weight and length, and changes in phase composition of carbonated compacts of LFSU in four different environments (distilled water, room temperature; 100% relative humidity, room temperature; 60% relative humidity, 25 °C; exterior) during one year after carbonation were studied. A tendency of compressive strength increase in the first six months after carbonation and a decrease in compressive strength after one year from carbonation was observed in all environments. The long-term increase in compressive strength was mainly caused by hydration of -C2S and mayenite. The decrease in compressive strength after one year could have been caused by hydration of MgO to Mg(OH)2. This, however, was not clearly proved.
Reactive powder concretes (RPC) with polymer latexes
Petrů, Ludmila ; Koplík, Jan (referee) ; Šoukal, František (advisor)
This thesis deals with the effect of polymeric latexes on the properties of concrete based on reactive powders. Three types of commercial latexes were used for the preparation of the samples, namely Revacryl, Duvilax and Plextol. Revacryl AE 2091 is an aqueous dispersion of styrene-acrylate copolymer with a high content of solids. Duvilax BD-20 is a homopolymer polyvinyl acetate dispersion that does not contain fillers with plasticizers. Plextol X 4002 is an aqueous, self-setting acrylic emulsion with a high content of solids. These latexes were added to the samples at concentrations of 0,20; 0,40; 0,60; 1,20 and 2,50 %. To determine the effect of latex on processability, the flow rate of the fresh mixture was measured. The main objective was to determine the ballistic resistance of modified concretes based on reactive powders. The DOP test was used for the determination. Furthermore, the change in mechanical properties was determined by adding a polymer to concrete based on reactive powders. The improvement in properties is expected to be due to the formation of a polymer film and a polymer-cement co-matrix. To demonstrate the film formation, the microstructure of the samples was observed by a raster electron microscope.
Praparation and characterization of calcium aluminate hydrates
Hubáček, Václav ; Švec, Jiří (referee) ; Koplík, Jan (advisor)
This thesis deals with the preparation of pure calcium aluminate phases, specifically CA, CA2, C3A and C12A7 by two different methods - the solid state synthesis and the amorphous citrate method. The hydration of these phases at different temperatures was also studied The effect of the phase preparation method used and the simultaneous effect of temperature were observed on the prepared hydrates, using suitable analytical methods. The characterization and identification of the prepared phases and their hydrates were studied by X-ray diffraction analysis, Fourier transform infrared spectroscopy, scanning electron microscopy and simultaneous thermogravimetric and differential thermal analysis. The prepared hydration products were mostly identified in accordance with the literature data. TGA/DTA of the prepared hydrates helped to clarify some of the hydrate decomposition processes, especially for the hexagonal hydrate CAH10 and the cubic hydrate C3AH6, which were prepared in a sufficiently pure form suitable for analysis.
Combined aluminium-silicon based sol-gel binding system for refractory
Taraba, Vojtěch ; Koplík, Jan (referee) ; Švec, Jiří (advisor)
The following piece of work deals with the use of a combined aluminium-silicon based sol-gel binding system for refractory. The effect of different gelling agents on the gelation process was observed and rheometric measurements were performed for MgO. After optimizating the drying process, the resulting gel was characterized by thermal analyses, based on which the firing temperatures were selected. Qualitative analysis of the gels fired to the selected temperatures was performed using FTIR. Using XRD, the semi-quantitative phase composition of the samples was monitored as a function of firing temperature. The topography of the test bodies prepared based on results of the previous analyses was later observed using a scanning electron microscope.
Development of the material for solidification based on carbonation of waste materials
Mikulová, Mária ; Koplík, Jan (referee) ; Másilko, Jiří (advisor)
The aim of this thesis was to create a material by solidification of waste materials from steel production. Ladle furnace slag (LFS) pre-treated by demetallization was used as a binder, Fe sludge and a mixture of slags and debris (MSD) coming from Třinecké železárny were used as fillers. The binding properties of LFS are the result of a high content of calcium silicates, which are able to react with CO2 and thus create carbonates, mainly calcite (CaCO3), which act as a binder – this process is called carbonation. Firstly, an effect of substitution of LFS by individual fillers on compressive strength of carbonated testing samples was examined. Based on these results, three solidified materials were proposed, of which compressive strength immediately after carbonation and after 28 days was observed. Leaching behaviour, weight gain of the samples after carbonation, their mineralogical composition, and carbon content were examined as well. Compressive strength of all three solidified materials raised above required 10 MPa after 28 days. Pure carbonated LFS was used and analysed as a reference sample.
Hybride binders based on the high-calcium ash
Hubáček, Václav ; Cába, Vladislav (referee) ; Koplík, Jan (advisor)
The goal of this bachelor´s thesis was to develop a hybrid binder based on high calcium fly ash with the focus on addition of Portland cement, observation of hydration process, measurement of mechanichal properties, identification of hydration products and comparation with Portland cement. Hybrid binder was developer by adding different amounts of Portland cement to the selected mixture of high calcium fly ash activated by sodium hydroxide. Setting times and flexural strength and compressive strength were measured for these hybrid binders. Afterwards one type of hybrid binder was selected for more analyses (XFR, XRD, SEM/EDS and isothermic calorimetry). These analyses were also used for a sample of Portland cement and alkali activated high calcium fly ash and afterwards these three samples were compared between each other. The collected data show that the compositions of the activated fly ash and hybrid binder are very similar and the addition of Portland cement to the mixture has only a minor impact. Main hydration product for both of them was ettringite. Addition of Portland cement to the activated high calcium fly ash has positive impact on mechanical properties, it shortens the start of setting time of a mixture and it also increases early and later compressive strenghts.
The binder based on the high-calcium ash - the influence of the alkali activator
Šichnárek, Vojtěch ; Kotrla, Jan (referee) ; Koplík, Jan (advisor)
The aim of this thesis was examination of the influence of different alkali activators to final properties of binders based on fluidized bed combustion fly ash. There were prepared mixtures containing sodium waterglass or sodium carbonate. Curing time, consistence, and strengths after 2, 7, 14 and 28 days were measured. X-ray diffraction and X-ray fluorescence were used to find out the composition of samples. There were taken images and element spectra using scanning electron microscope and isothermal calorimetry was used to determine the heat flow during the time of curing. The results indicate that the use of water glass achieves better initial workability and pressure strengths are higher than besides sodium carbonate. However, when sodium carbonate is used, pressure strengths are lower, but they are less dependent on the amount of the activator and do not change as much with time. Crystallographic composition is dependent to the activator used – by using sodium waterglass there was more of ettringite and portlandite in the sample.
The development of the solidification material from hybrid cement based on slag
Valach, Jakub ; Janča, Martin (referee) ; Koplík, Jan (advisor)
The bachelor thesis is focused on the research and development of hybrid cements based on slag. The base is granulated blast furnace slag, which serves as a substitute for cement, cement is used as an admixture. Various additions of cement and activator are monitored. The mixture is activated by Caustifying limestone. Firstly, the strengths of the mortars are mixed and measured without the addition of cement in order to find a suitable ratio of activator and slag. Subsequently, I focused on mixing and measuring the strength of mortars with the addition of Portland cement and I looked for suitable samples, which I analyzed by XRD, EDS, SEM. I also determined their stiffening time, lavish and volume stability.
The study of hydration of RPC (Reactive Powder Concretes) in hydrothermal condition
Dvořáková, Tereza ; Koplík, Jan (referee) ; Šoukal, František (advisor)
The diploma thesis deals with the study of hydration of reactive powder concrete under hydrotermal conditions. The theoretical part describes the properties of materials and additives used for the preparation of mixtures. The following describes the principles and requiments for the materials for preparing the reactive powder concrete. The practical part is studied design method mix and the impact of materials to the consistency of paste. The effect of cample placement on flexural and compressive strength of the prepared mixtures was observed. The samples were stored under standart laboratory conditions and under hydrothermal conditions. The phase composition of the samples was monitored by X-ray diffraction analysis and the mocrostructure by scanning electron microscopy.

National Repository of Grey Literature : 44 records found   1 - 10nextend  jump to record:
See also: similar author names
2 Koplík, Jerguš
2 Koplík, Jiří
Interested in being notified about new results for this query?
Subscribe to the RSS feed.