National Repository of Grey Literature 104 records found  beginprevious89 - 98next  jump to record: Search took 0.01 seconds. 
The optimization of phosphate binders compozition used for refractories
Kalousová, Hana ; Ptáček, Petr (referee) ; Opravil, Tomáš (advisor)
This thesis deals with optimization of the composition phosphate binders. These binders are used in production of refractories. In this branch, the bauxite is very often used as an aggregate, but it contains tiny particles of iron which arise in milling process. These particles of iron react with the phosphate binder to form hydrogen – it is consequence of the reaction between phosphoric acid and iron. The formed gas causes the formation of bubbles and the deformation of refractories. The goal of this thesis is to find suitable additives which can be used to stop or to limit the production of hydrogen. Usually used binders were replaced by a model binder to simplify the system and for better understanding. The model binder was prepared in laboratory by dissolving aluminium hydroxide in phosphoric acid. They used pure powdered pentacarbonyl iron instead of tiny iron particles from the milling process. The model binder was modified with using a few inhibitors. The calcimetr was used to measure their influence on the production of hydrogen, as well as measuring concentrated rows of selected inhibitors. These rows are necessary to optimize the inhibitors quantity added in the binder.
Industrial sludges as alternative fuel in cement plant
Raška, Miroslav ; Kalina, Lukáš (referee) ; Opravil, Tomáš (advisor)
This thesis deals with the use of industrial sludge as an additive to alternative fuels in the cement industry. The first part is focused on solid alternative fuels, especially sewagesludge, processed and used in the firing process of Portland clinker and heatingpotential of the secondary raw materials, fuels. The second part deals with the history, production of cement and its raw material base. The last part contains information of practical measurements and draw conclusions about the appropriateness of using that type of industrial sludge in cement as a solid alternative fuel.
Possibilities of roman cements preparation by modification of limestone sludges
Petr, Jiří ; Koplík, Jan (referee) ; Opravil, Tomáš (advisor)
It is obvious that binders based on the portland clinker will still play the most important role in the building materials industry. Their high quality, the existence of standards and the affordability are the main reasons. Together with this there is of course an appreciable need for decreasing of energy consumption, carbon dioxide emissions and utilization of secondary raw materials. The roman cement is the possible answer to all of these requests. This historically experienced hydraulic binder, relatively less demanding for the quality of the raw material, is fired by the temperature below the sintering point and even though it does not achieve as good mechanical properties as the portland cement does, in some applications it could be re-established. This would ultimately lead to considerable savings both in the energy and the carbon dioxide emissions.
Effect of ground limestone addition on properties of cement-slag binder systems
Bílek, Vlastimil ; Másilko, Jiří (referee) ; Opravil, Tomáš (advisor)
This thesis deals with the effect of ground limestone addition on properties of cement-slag binder system. The evolution of compressive and flexural strength of binary and ternary systems (pastes), where 25 % of cement was substituted by one or two admixtures in different ratio, were determined and mutually compared. Granulated blast furnace slag and three different limestones were these admixtures. Two of that limestones were natural and one was prepared by a precipitation. For comparison, mixtures, where ash was added insted of slag, were prepared. The mechanism, by which finely ground limestone participates in hydration process, was studied by conduductometric measurements of systems simulating conditions in fresh pastes, and by TG-DTA method, which was used to determination of added limestone amount which remains in its original form and the amount which participates in the formation of hydration products.
Color possibilities of artificial sandstones based on geopolymers
Lattenberg, Pavel ; Kalina, Lukáš (referee) ; Opravil, Tomáš (advisor)
This thesis deals with the possibility of preparing artificial sandstone based on geopolymer matrix and ways to achieve a natural appearance and good mechanical properties. The theoretical part is devoted to the current state of knowledge in the field of geopolymers and their recovery potential, but also the natural sandstone and its geographic diversity. The practical part deals with the preparation of various types of binding systems based on metakaolin, ground blast furnace slag and water glass. Their comparison, and the possibility the appearance and characteristics change in the composition of the filler.
Supersulphates cements
Mohelská, Lucie ; Wirthová, Michaela (referee) ; Opravil, Tomáš (advisor)
The work is studying posibilities of use secondary materials produced by energetical industry. In fact it studies posibilities of preparing supersulphates cements with secondary raw materials. Its main system for simulation was used milled portland clinker. To clinker were added diferent secondary raw materials from energetical industry with sulphate. On prepared samples were watched mechanical properties in time. Tested were different samples of secondary raw materials.
Utilization possibilitiesof foundry sands in geopolymers systems
Kopecký, Filip ; Másilko, Jiří (referee) ; Opravil, Tomáš (advisor)
Considering increasing manufacture of cast iron, steels and other metallic materials made in foundries increases also production of waste foundry sands. Foundry sands that remain after moulding and can not be reused in the prouction process are usually not recycled nowadays and in the better cases they are clasified as a fill materials. Becouse these secondary raw materials are produced in relatively big amounts it is apropriate to search for their effective reuse. One of the possibilities is using of this materials in buliding industry. Thanks to their constitution and properties we can consider the possibilties of an alkaline activation. Thats why this work discusses the possibilities of the alkaline activation of the waste foundry sands.
Modern Inorganic Building Materials Free of Portland Cement
Sadílek, Jakub ; Opravil, Tomáš (referee) ; Zmrzlý, Martin (advisor)
This bachelor’s thesis is focused on properties of modern construction inorganic ma-terials – geopolymeric concretes. In introductional part of work it is described basic theoretical background, as properties of binders, principles of setting and hardening. For preparation of geopolymer matrix was used secondary or waste materials of energetic and metallurgical industry – fly ashes and slags. In laboratory were prepared four com-positions of geopolymeric concretes combined from geopolymeric matrix with constant compostition and variable composition of aggregates. As aggregates these materials were used: three fractions of quartz sand, steel furnace slag and in one composition also crystals of mineral wollastonit. It was discovered that the use of steel furnace slag as aggregate in geopolymeric concrete has positive influence mainly to compressive strength, but the addition of wollastonite mineral do not evocate expectable increase of mechanical properties of samples.
Solubility of power plant fly ashes in high-alkali environment
Kejík, Pavel ; Opravil, Tomáš (referee) ; Šoukal, František (advisor)
This work deals with study of alkali activated ashes from high-temperature and fluidized bed coal combustion in thirteen powerplants in Czech republic. A solution of 50% sodium hydroxide was used as an alkali activator in this case. Because the two main elements of these secondary raw materials are silica and aluminum, the main part of the work is study of their evolution to solution and dissolve time dependence. The second part is comparing of the phase composition of powerplant ashes before alkali activation and after that.
Possibilities of clay plasters shrinkage elimination
Melichar, Jindřich ; Koplík, Jan (referee) ; Opravil, Tomáš (advisor)
Earth plasters which are applicated in interiers don´t have just an estetic, but mainly heat storage function. To accomplish better storage properties the plaster has to be laid on the wall in sufficient thick ply. But this use to be accompained by creating of cracks during dehydration of the plaster. This bachelor work will be considering possibilities of elliminating this negative event by additing suitable components to suppress shrinkage and cracks by creating ettringite.

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