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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
511

Vývoj nových injektážních hmot pro rubovou injektáž kanalizací / Development of new grouting materials for reverse grouting of sewers

Dolák, Martin January 2021 (has links)
ABSTRACT This thesis deals with the development of silicate based reverse grouts for the purpose of rehabilitation of sewers. The work also examines the possibility of substitution of basic input raw materials with secondary raw materials, meaning replacements of both filler components and binder components. As secondary raw materials, we refer to wastes from the production process which, after the necessary treatment, are used in another production. The development and experimental verification of the functionality of the developed grout was focused mainly on the use of secondary raw materials as much as possible, while maintaining or even improving its physical and mechanical properties. Based on the results of the work, it can be stated that with a 100% replacement rate of filler components in combination with 20% replacement rate of binder components, it is possible to largely maintain the properties of the material, or even optimize them. The results of the thesis also point to the possibility of reducing the economic and environmental demands of production of building materials.
512

Aplikace analytických metod využívajících RTG záření v oblasti analýz stavebních materiálů / The application of analytical methods based on X-rays in analysis of building materials

Klekner, Martin January 2012 (has links)
Master’s thesis mainly deals with XRF analysis of building materials. Comprehensively analyzes the factors that limit the accuracy of the obtained data, creates a new methodology for the rapid analysis of silicate materials by XRF instrument and discusses the influences determining the reproducibility of the results of XRF analysis.
513

Změna trvanlivosti betonu z recyklovaného betonu variantní adicí silikátových příměsí / Change in the durability of concrete made of recycled concrete by alternative addition of ceramic admixtures

Stavař, Tomáš January 2013 (has links)
The master thesis dealing with problematic about durability of concrete, with use of recycled concrete and addition of silica additions. Predominant for resistance of concrete constructions is surface layer, through which aggressive gasses and liquids penetrate from surrounding environment. The most important indicator of concrete durability is ability of surface layer transmissions of aggressive substants. In experimental part will be defined the actual state of surface layer by normal testing methods. The transmissions of surface layer will be tested on concrete cubes. Tests for transmissions of air (method TORRENT), of water (method ISAT), of acid gases (dept of carbonation by quick test in 98% CO2) will be carried out and also strength tests. Assessment of positive or negative influence of additions and amount of cement on durability and mechanical properties of concrete will be discussed in conclusion.
514

Vývoj kompozitů na bázi anorganických pojiv určených pro extrémní aplikace / The development of composites based on inorganic binders designed for the extreme applications

Janoušek, Petr January 2013 (has links)
The topic of this master's thesis is the development of composite materials based on inorganic binders for use in extreme conditions. It means especially geopolymeric or alkali activated materials (AAM) based composites. The theoretical part of this thesis summarizes knowledges about the development and use of alkali-activated materials, their structure and mechanisms of their formation. It also deals with the applicable raw materials for AAM and their exciters, which are in particular water glass and sodium hydroxide. There also have been a summary of the effects of high temperatures and chemicals on the mechanical properties of AAM and the requirements of standard EN 1504-3 for repairing materials. The task of the practical part was to develop a repair mortar for concrete structures based on AAM so that its production was as simple as possible, ie one-component materials. Gradually six recipes have been develeoped. Test specimens made from these recipes have been putted to selected tests according to the requirements of ČSN EN 1504-3.
515

Návrh koncepce využívání mikropříměsí pro betony vysokých užitných vlastností / Proposition of conception of using micro-additions for High Performance Concrete

Lédl, Matěj January 2014 (has links)
The modern, contemporarily used cement composite types make use of various additives. This diploma thesis is focused on designs of mortars that have been enriched with micro and nano additives, which lead to higher mechanical strength through optimized grading of mortar mixes. This thesis also evaluates the influence of material properties on resulting properties of mortars in fresh and hardened state.
516

Namrzavost zemin a druhotných materiálů v podloží vozovek / Frost susceptibility of soils and waste materials to pavement subgrade

Sokolová, Veronika January 2015 (has links)
Destruction of road constructions due to the frost is in locations with temperatures under the zero a problem which leads to permanent deformation. The theoretical part of this thesis deals with the freezing process of the pavement and its subgrade. It presents methods for determining the rate of frost susceptibility in both the Czech Republic and abroad. Describes the materials used in the subgrade of roads and their suitability in terms of frost susceptibility. The thesis closely examines the fly-ashes, their properties and possibilities of using in the construction industry. The practical part of the thesis focuses on the performance of direct laboratory frost heave tests, immediate bearing index tests, California bearing ratio tests and cyclic load triaxial tests to determine the modulus of elasticity. Tests are carried out on the soil, the soil mixtures with certain percentages of fly ash from different sources at the same soil treated with lime. Then the results are compared and dependence between the measured characteristics of materials is created.
517

Vývoj vysokopevnostních betonů definovaných vlastností s využitím druhotných surovin / Development of high-strength concrete defined properties with the use of secondary raw materials

Ondráček, Michal Unknown Date (has links)
Civil engineering development is connected with the application of new construction methods and the development of new building materials. Concrete, as one of the basic building materials, is part of this development. A major turning point in the development of concrete and its properties occurred with the use of new, more efficient plasticizing additives. This allowed to produce concrete with lower water cement ratio, while increasing the strength of concrete. Gradually, the compressive strength of concrete boundary has moved by several levels, when there are currently commonly used concrete with strength of about 100 N/mm2 and with the special methods of concrete production strength range from 250 to 300 N/mm2. A negative aspect of the development of (ultra) high-strength concrete is their energy and economic demands. A characteristic feature of high-strength concrete is a high content of cement and very fine admixtures, especially silica fume. One way to improve the economics of these types of concrete is the application of cheaper admixture based on industrial waste. The content of this work is the observation and description of the properties of high-strength concrete and reactive powder concrete, in which the admixtures were based on industrial waste were applied. Part of this work is the comparison of economic parameters for individual types of concrete.
518

Vliv zinku přítomného ve vedlejších surovinách na hydrataci a vlastnosti portlandských směsných cementů / Influence of Zinc in Byproducts on Hydration and Properties of Blended Portlands Cements

Šilerová, Iva January 2015 (has links)
The theme of this work is to monitor the effect of zinc on the properties of blended Portland cements. Zinc was tested in the form of two-soluble salts: Zn(NO3)22 H2O and ZnCl2 and a very slightly soluble compound ZnO. Blended cements were prepared by partial replacement with finely ground granulated blast furnace slag, high-temperature and fluidized bed combustion filter fly ash. Flow properties were studied on the prepared pastes. Impact on hydration reactions was examined by using of isothermal and isoperibolic calorimetry. Flexural and compressive strength were measured as mechanical properties of the prepared test specimens. The phase composition of the prepared composites and incorporation of zinc ions in the cement matrix via leaching tests and FTIR analyzes were also studied. Microstructure development of cement samples was tested by SEM analysis with EDS. Influence on ecotoxicity was also measured.
519

Vliv technologie výroby popílkového pórobetonu na vznik tobermoritických fází / The effect of fly ash aerated concrete production technology to formation of tobermoritic phases

Fleischhacker, Ján January 2016 (has links)
Autoclaved aerated concrete is long-time ecological building material with usefull properties. There needs to be done research of its mineralogical compound for reengineering the production. The main mineral compound of AAC is tobermorite, it increases its mechanical properties. In the presence study, we examine the usage of nature and artificial silicious materials. Also, we investigate the influence of sulfate and alumina admixtures, as well as fluidized bed combustion ash, which can be used as the lime and gypsum replacement. Closure of the study is design of the optimal raw material composition, also hydrothermal treatment of autoclaved aerated concrete. In relation to its mechanical properties, mineralogical composition and cost.
520

Quantification of the bioccumulation potential of various chemical elements from coal fly ash using Brassia juncea and Spinacia oleracea L and its implication for phytoremediation of coal fly ash dumps

Mashau, Aluwani Shiridor 18 September 2017 (has links)
MENVSC / Department of Ecology and Resource Management / South Africa is highly dependent on coal for production of electricity. The combustion of coal for electricity generation produces waste by-products which include fine ash (fly ash) and coarse ash. Fly ash (FA) is produced in large amounts while its utilization is low due to its classification as a hazardous material. Sasol produces about 7 million tons of FA, while Eskom produces about 28 million tons of coal FA annually. FA is a fine by-product from pulverized coal with detrimental effects on plants, soil or land, animals and human beings, and pollutes the air. The present investigation focuses on the examination of the chemical elements bioaccumulation and phytoremediation potential of Indian mustard (Brassica juncea) and Spinach (Spinacia Oleracea L). X-ray fluorescence (XRF) was used to analyze the elemental composition of FA and soil, Scanning Electron Microscope (SEM) to examine the morphology, while X-ray diffraction (XRD) analysis was used to evaluate the mineralogy of FA. The concentrations of metal and non-metal species that are released from FA on contact with water at different conditions were quantified using ICP-MS. Pot culture experiment was conducted to grow Brassica juncea and Spinacia Oleracea L. using FA and soil as growth medium. Leachates from the pots were collected and analysed using ICP-MS. Plant parts from harvested Brassica juncea and Spinacia Oleracea L. were cut separately and analysed using ICP-MS for the concentrations of different metal and non-metal species in plant parts. Plant parts were also used to estimate biomass and chlorophyll content (leaves). To prepare these plant samples for analysis, the powdered plant sample (0.5 g) was digested through aqua regia (HCL:HNO3 = 3:1 (v/v)) to near dryness using hotplate and filled to 100 mL of MilliQ water. The samples were filtered and directly used to determine the chemical elements concentrations. Blanks and internal standards were used for quality assurance during analysis. Chemical elements that are present in FA and sometimes in higher concentrations are associated with detrimental effects in plants, animals and human beings, hence phytoremediation is vital. Bioconcentration factor (BCF) was used to estimate the metal species accumulation ability of the plants from the FA, FA/soil mixtures, while translocation factor (TF) was used to assess the plant species potential for phytoremediation of coal fly ash dumps. Analysis of Varience (ANOVA) was used to statistically test data using Graphpad software package. Relationship between chemical elements in soil, FA and FA+soil growth media and also different plant parts (root, stem and leaf) of B. juncea and S. Oleracea L were calculated using the t - test, ANOVA-Bartlett test, Mann-Whitney Test and Kruskal-Wallis Statistic (KW) depending on each data set. The physicochemical characterization of coal fly ash showed that FA from Grootvlei power station can be classified as class F with an alkaline pH level of 10.62. It showed that particle morphology of this FA had a lower degree of sphericity with irregular agglomerations of many particles while there were dominant spherical particles and smaller sharp needle like particles. It is also an alumino-silicate material as confirmed by the high SiO2 and Al2O3 content, while soil leachates had an average/neutral pH of 7.22 with very high amounts of Si. In both soil and FA, elements that were expected to be readily available to plants included Ca, Si, K, Ba, Mo, Na, Al, Mg, Sr and non-essential elements (Si, Ba, Na, Al, Sr), which, if uptaken by plants’ roots can have negative impacts in plants. Physicochemical analysis of soil, FA and FA+soil leachates showed that the alkalinity of the FA changed over time and there was also a decrease in the EC due to dissolution iv of soluble major oxides, which was promoted by continuous water irrigation. The soil and FA+soil growth media showed similar results. Chemical elements like B, Mn, Fe and Ba were occurring at higher concentrations in leachates for most weeks in the pot culture experiments. However, it was observed that in the eleventh week of leachate collection all these chemical elements decreased to very low concentrations. This suggest that these chemical elements can be reduced over time as plants are being irrigated which is either due to uptake by plants or washed off with water. Statistically, there was a significant difference for different chemical elements of leachates from different growth media for each plant species (B. juncea and S. Olearcea L.). The overall growth rate shows that S. Oleracea L was better than that of B. juncea especially in the FA media over time, while the biomass of the two plant species showed similar results. After all, even though S. Oleracea L had carotenoid content below detection limits, it had higher chlorophyll b than B. juncea for all growth media in general. But, statistically there was no significant difference between the two plant species in terms of growth rate and biomass; even between the plant parts denoting similar growth performance for the two plant species under study. The bioaccumulation potential of the two plant species showed that chemical elements such as Fe, Mn, Ba, Zn and B were highly accumulated by the different parts of the plants. However, the chemical elements such as of Mo, Ni, Cu, and Cr showed the least concentrations. This trend was similar for all growth media and both plant species but this changes over time for different growth media and plant species as increasing and decreasing trends can be noticed. This led to no significant difference between plant species and also growth media, statistically. High BCF values of Fe, Mn, Ba, Zn and B were observed in the different parts of the plants for both plant species. However, Mo, Ni, Cu, and Cr had BCF values less than 1 for most growth media over time. BCF values in plant parts differed with time, growth media and plant species. Translocation of chemical elements shows that the B. juncea plant proved to be an effective phytoremediation plant species since it is effective in translocation of many chemical elements for different growth media to shoots while S. Oleracea L failed to translocate most chemical elements from stem to leaves although it translocated some from root to shoots. Hence, it can be concluded from the study that both species can be used in phytoremediation of coal fly ash dumps but with B. juncea being the most effective accumulator and translocator of many chemical elements. However, it can be recommended that chelating agents like ethylene diamine tetra acetic acid (EDTA) be introduced to solubilize chemical elements from growth media matrix into growth media solution to facilitate the quick transport of chemical elements into xylem, and increase

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