National Repository of Grey Literature 98 records found  beginprevious88 - 97next  jump to record: Search took 0.00 seconds. 
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.
Volume changes of concrete based on reactive powder components and possibilities of their regulation with chemical admixtures
Hlaváček, Jaroslav ; Kalinová, Helena (referee) ; Opravil, Tomáš (advisor)
Very high strength of RPC allows them to an unusual extreme possibilities of their applications. Volume change (shrinkage) negatively affects their relatively broad range of applications, particularly in applications which are used for filling tubes or other components. In today's advanced time with plenty of chemical ingredients and additives on the market (such as the expansion component) could be a side effect of this largely eliminated, or removed entirely. Only some components of the expansion will be appropriate for RPC cements. This reaserch investigates the expansion of ingredients on the basis of sulfates and monitors not only volume changes, but also the strength characteristics and tolerability of the tested anchors tested with a matrix component of the expansion.
Possibilities of alcali activation of steel slag
Frýbortová, Iva ; Rovnaník, Pavel (referee) ; Opravil, Tomáš (advisor)
The properties of alkali activated steel slag as a clinker-free binder system was studied in this thesis. The aim was to find the optimal composition of alkaline activator providing good properties of the prepared binder. Sodium and potassium hydroxides and alkaline silicates in the form of solutions and powders were used as the activators. Mixture of steel slag, fluidized bed coal combustion ash and water without any activating ingredient was another binder system studied in this work. Mechanical properties, such as compressive and flexural strength, of the mixtures were determined. Calorimetric measurements were used for the study of hydration process, scanning electron microscopy for the examination of microstructure.
Study of synthetic sandstones preparation possibilities
Solik, Jaroslav ; Kalina, Lukáš (referee) ; Opravil, Tomáš (advisor)
This thesis explores the possibility of developing synthetic sandstones based on alkaline-activated (geopolymer) binders. The goal is to design an appropriate connective system of optimal concentration, so that the prepared material (artificial stone) showed similar characteristics as natural. The experimental section summarizes the experiments that explore several different alkali connective systems. The aim is to compare the properties of binders prepared from methakaolin (Mefisto K-05 and L-05) alkali-activated by sodium or potassium water glass. For comparison with these connective systems were also prepared samples of commercially supplied geopolymer binder called Baucis
Reactivity and controll of properties of metallic materials
Ševčíková, Barbora ; Opravil, Tomáš (referee) ; Zmrzlý, Martin (advisor)
The main objective of the bachelor thesis is to investigate the reactivity and corrosion of materials, namely of magnesium alloys. The theoretical part comprises a brief summary of the existing knowledge on magnesium alloys in the field of metal corrosion and a description of essential properties of the examined and utilized material. These are followed by the protection technology and a material resistance analysis including the specification of the processes applied in the experimental part. The thesis is focused on a comparison of the microstructure and corrosion resistance of magnesium alloys AZ31, AZ61 and AZ91. The applied methodology lied on metallography preparation of light optical micrographs of the surface-region cross-sections and on corrosion tests. These were carried out in 3% sodium chloride solution where the samples were immersed for the period of 8 hours.
Preparation of geopolymeric binders based on power plant fly ashes
Jevická, Lucie ; Opravil, Tomáš (referee) ; Šoukal, František (advisor)
This thesis deals with preparation of geopolymeric binders based on power plant fly ashes by alkali activation. It studies influence of different types ashes content in pastes on setting and final properties of geopolymeric binders. The aim of study is determination of optimal ratio of raw materials to reach the best possible characteristics of final binder. Ashes from high-temperature and fluidized bed coal combustion were used for experimental works. Mass content of ashes in tested mixtures and total ratio of oxides crucial for polycondensation and geopolymeric structure formation were chosen as major input parameters. Calorimetric measurements of tested mixtures fresh pastes were implemented to learn about setting process. Hardened binder specimens were tested for bending and compressive strength.

National Repository of Grey Literature : 98 records found   beginprevious88 - 97next  jump to record:
Interested in being notified about new results for this query?
Subscribe to the RSS feed.