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Study of possibilities of activation of power plant fly ash as an active ingredient in concrete
Máša, Jiří ; Uher, Vojtěch (referee) ; Hela, Rudolf (advisor)
Global concrete production is increasing, which brings some environmental burden. A certain solution is the use of secondary raw materials, which has been a long-standing practice in the construction industry. One of the most widespread secondary raw materials is power fly ash. However, in recent years trends have been directed towards maximizing their utility properties. The aim of this work was to study the possibilities of activation of power plant fly ash as an active admixture in concrete. The thesis is divided into two parts, the theoretical and the practical part. The theoretical part describes in detail the possibilities of power plant fly ash activation for use as an active admixture in concrete. The practical part of the thesis is focused on mechanical activation, where the knowledge of the theoretical part is verified on various fly ash.
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Optimizing the composition of micro concrete admixtures.
Juříková, Denisa ; Křížová, Klára (referee) ; Hela, Rudolf (advisor)
The aim of this paper is to summarize knowledges related to the use of fine-grained admixtures in cement composites. By utilizing of these admixtures it is possible to achieve extreme properties, especially high strenght and durability of concrete. These properties can be achieved by optimizing the density of the binder and filler in range of 0 to 0,25 mm. Therefore, large part of thesis is focused on admixtures and its effect on concrete. The experimental part of the thesis deals with optimization od selected admixtures in combination with cement to achieve the minimum of the voids and their compressive strenght were determined at 1, 3, 7, 28 and 60 days.
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Verification of durability of ash concrete in the environment XF
Kušiak, Petr ; Hela,, Vlastimil (referee) ; Hela, Rudolf (advisor)
Fly ash is now much used as an admixture to concrete. This master´s thesis focuses on the use of fly ash as an active admixture in concrete environment for XF. The thesis has two parts. The first part collected theoretical information about the origin and behavior of fly ash in fresh and hardened concrete. In the second part was experimental verification of these characteristics. The purpouse of this thesis is to demonstrate that the fly ash attribute to meet all environmental XF.
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Concrete with fly ash for XF3 and XF4
Máša, Jiří ; Ťažký, Martin (referee) ; Hela, Rudolf (advisor)
This bachelor thesis deals with concrete using fly ash as an active ingredient for environment XF3 and XF4. Bachelor thesis is divided into two parts. The first, theoretical part, is focused on basic information on power generation of fly ashes and solves the existing knowledge about concrete with partial asphalt replacement and then evaluates their properties both in fresh and condensed state. Below are the world-wide knowledge of the behavior of these concrete. The second part deals with the experimental verification of these findings contained in the theoretical part. The aim of this work is to verify the durability of concrete with fly ash for XF3 and XF4 environments.
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Optimizing the use of active admixtures in mixed cements and determining the k value
Kužílková, Hana ; Hubáček, Adam (referee) ; Hela, Rudolf (advisor)
The goal of this bachelor's thesis is to examine the possibility of using admixtures as a partial substitute for cement in concrete. The thesis examines the replacement of cement with three specific additives: micronized limestone, power plant fly ash and blast furnace slag. When using an admixture as a partial replacement for cement, the addition of the admixture affects the properties of both fresh and hardened concrete. The theoretical part of the work is devoted to the description of admixtures and their influence on the properties of fresh and hardened concrete. Furthermore, basic information on the efficiency index and k-value is presented. The aim of the practical part of the bachelor's thesis is to determine the efficiency indices of the given additives as well as their k-values.
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Genetic consequences of bottlenecks and population admixture in Eurasian beaver (Castor fiber)
Náhlovský, Jan ; Munclinger, Pavel (advisor) ; Hulva, Pavel (referee)
In the last few centuries beavers passed through dramatic declining of the population size followed by expansion supported by reintroductions. The genetical variability is much decreased due to this bottleneck. Current beavers possess 31 known recent mitochondrial haplotypes, among which some were described independently several times. The haplotypes form two clusters, which serve as a base for dividing beaver populations into the west and east ESU. While microsatellite loci show moderate variability, the diversity of Y chromosome loci is very low. There are only ten described alleles of the DRB second exon, which belong to the MHC loci. No mitochondrial haplotype or MHC allele is shared between relict populations. This is not noticeable in samples from the time before the bottleneck. Described subspecies are therefore only the artefact of the recent bottleneck. Newly established populations comprise in many cases beavers of various origin and are more or less admixed. It seems, that the admixed populations have higher viability and conversely in some relict populations it is possible to find the evidence of the inbreeding depression. Thus, for reintroductions it is advantageous to use individuals from several source relict populations or to use beavers from admixed populations. Several species passed...
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Influence of Water-Retentive Admixtures on the Adhesive Strength of Mortars
Žižlavský, Tomáš
The article studies the influence of viscosity-modifying admixtures with water-retentive function on the adherence of natural hydraulic lime-based mortars to traditional fired-clay brick substrate. The substrate was either dried or water-saturated. High water retention value and water/binder ratio led to inferior performance while applied on saturated substrate. On the other hand those properties were found beneficial on the dried substrate. The failure in the mortar during the pull-off test is far more common while the mortars are applied on dried substrate. Each of the admixtures studied proved to be useful in improving the performance of the mortar in at least one of the studied conditions.
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Technical and economic comparison of usability of different types of cements
Kováč, Michal ; Ťažký, Tomáš (referee) ; Hela, Rudolf (advisor)
This bachelor thesis deals with comparison of properties of different types of cements. The theoretical part is devoted to the distribution of cements, their composition and production. Various properties of cements are detected and compared in the practical part. Furthermore, concrete formulas are created which are also mixed and tested. Finally, the proposed area for the test cements and economic evaluation per 1 m3 of concrete mix.
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Study of possibilities of activation of power plant fly ash as an active ingredient in concrete
Máša, Jiří ; Uher, Vojtěch (referee) ; Hela, Rudolf (advisor)
Global concrete production is increasing, which brings some environmental burden. A certain solution is the use of secondary raw materials, which has been a long-standing practice in the construction industry. One of the most widespread secondary raw materials is power fly ash. However, in recent years trends have been directed towards maximizing their utility properties. The aim of this work was to study the possibilities of activation of power plant fly ash as an active admixture in concrete. The thesis is divided into two parts, the theoretical and the practical part. The theoretical part describes in detail the possibilities of power plant fly ash activation for use as an active admixture in concrete. The practical part of the thesis is focused on mechanical activation, where the knowledge of the theoretical part is verified on various fly ash.
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