|
|
The influence of storage conditions on the quality of fly ashes
Kalousová, Hana ; Koplík, Jan (referee) ; Opravil, Tomáš (advisor)
This thesis deals with the issue of influence of storage conditions on the quality of conventional fly ashes which are produced by combustion of lignite. These ashes were stockpiled for long time. A borehole for sampling was made in the fly ash stock-pile. Total depth of the borehole was 20 m. Samples of fly ashes taken from every single meter were analyzed and next mechanical properties and the volume stability of materials containing these fly ashes were tested. The quality of fly ashes especially with respect to the possibility to use them as components of pastes, mortars and concretes as pozzolanic admixture or fine filler was evaluated.
|
|
|
Floor systems based on secondary raw materials from power industry
Kalina, Martin ; Švec, Jiří (referee) ; Opravil, Tomáš (advisor)
This thesis deals with the possibility of using secondary raw materials from the energy industry especially the solid residues of high temperature combustion of coal. These materials should be now seen as a material with wide usage especially in the construction industry. One possibility of their usage is a replacement of binding parts in floor systems. The aim is to find the optimal composition of the mixture, which fits all the technical requirements and at the same time reduces the cost of its production. An advanced methods of powder X-ray diffraction analysis, particle size laser diffraction analysis and X-ray fluorescence analysis were used to determine the raw materials. Based on these analysis the experiments were designed focusing on the mechanical properties, the observation of the evolution of hydration’s heat in prepared mixtures and their time of setting and hardening.
|
|
|
The admixtures which are influencing setting time of portland cement
Hlaváček, Jaroslav ; Kalina, Lukáš (referee) ; Opravil, Tomáš (advisor)
During the production of concrete is important the careful selection of raw materials. Nowadays, we are trying in the production to minimize the economic burden and to maximize the use of secondary raw materials. This work is focused on the use of secondary raw materials from the energy industry in construction for the preparation of hydraulic binders. As the main raw materials were used different power plant fly ash from fluidized combustion. The composition of these secondary materials is quite different from conventional high-temperature ash, due to mixing with water they solidify and harden. Experiments were performed with three lodge fly ash from electrostatic precipitators of the fluidized combustion and one high-temperature fly ash. This work is focused on the possibility of monitoring the use of these secondary materials in construction, especially when tests were evaluated characteristics of strength and speed of setting and hardening.
|
|
| |
|
|
High-performance concretes based on the secondary raw materials
Sáček, Josef ; Brandštetr, Jiří (referee) ; Šoukal, František (advisor)
This work is devoted to study of physical-mechanical properties and structure of high performance concretes (HPC) based on portland cement. The attention is focused on possibility of substitution of economic high-cost components of concrete with utilization of secondary raw materials or cheaper components. Properties of raw materials and their influence on whole quality of concrete were tracked by various methods. Mechanical properties of prepared HPC samples were tested especially (compression and flexural strength) with further microscopic study of structure. Isoperibolic calorimetry and X-ray powder diffraction method were also used for concrete characterisation. These methods allowed to determine the influence of raw materials on prepared HPC and to carry out a certain optimization among price and quality of this material.
|
|
|
The reaction of ammonium bisulfate
Sedlák, Filip ; Bartoníčková, Eva (referee) ; Opravil, Tomáš (advisor)
This thesis studies reactions of amonium hydrogen sulfate. It studies chemical and physical properties of this not very examined compound. It deals with description of chemical reactions of thist compound. This thesis studies selected chemical reactions and describes its products. Object of this thesis is to find such reaction of ammonium hydrogensulfate that leads to stable product which would not leak ammonia in alkaline environment based on real experiments. Presence of ammonium hydrogen sulfate in solid residues of coal combustion is a result of inauguration denitrification technologies. A great percentage of fly ashes is used today in buildin industry for production of concrete. Fly ash containing ammonium hydrogen sulfate is unusable for this application, that is why searching for new solution to this incurred situation is needed.
|
|
|
Possibilities of using of ultra fine content of fly ash from clasical coal combustion
Havelka, Jaroslav ; Šiler, Pavel (referee) ; Opravil, Tomáš (advisor)
This thesis deals with the study of ultra fine content of fly ash from clasical coal combustion. It focuses mainly on the determination of properties of the fly ash – pozzolanic activity, chemical composition, particle size distribution and specific surface area. Possibilities of use of these fly ash were studied by preparation of cement mixtures with the fly ash and subsequent evaluation of physical properties and phase composition of the resulting composites. Phase composition was examined by x-ray powder diffraction.
|
|
|
The effect of particles size on the properties of mortars.
Sehnal, Tomáš ; Krátký, Josef (referee) ; Šiler, Pavel (advisor)
The consumption of concrete as a building material is still increasing over the world. Concrete production is closely associated with CO2 and other greenhouse gases emissions. The reduction of these emissions can be achieved by a higher utilization of secondary raw materials in cement mixtures. This bachelor work is focused on the using of secondary raw material, finely ground granulated blast furnace slag and fly ash from fluidized bed combustion and high temperature combustion. The properties of milling pure cement and cement mortars with addition of secondary raw material will be measured. Compressive strength, flexural strength, and calorimetric measurement will be performed for these prepared mortars.
|
|
|
Reducing the content of combustible substances in the flying ash
Mucha, Matej ; Špiláček, Michal (referee) ; Baláš, Marek (advisor)
The thesis deals with formation, usage, advantages and disadvantages of fluidized bed. It describes power plant Vojany, the process of generation power, used technology of fluidized bed boilers and their technical problems. The thesis summarizes the solutions given by University of technology Czestochova and also gives suggestion to solve the problem of large content of combustible coal parts in fly ash.
|
|
|
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.
|
guest ::
