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Influencing the pozzolanic reaction of silica fume in a high-performance cementitious composite
Všetečka, Tomáš ; Šoukal, František (referee) ; Novotný, Radoslav (advisor)
This work deals with the effect of cement hydration and pozzolanic reaction of a high-perfomrance cement composite containing Portland cement and silica fume as binder. Concentrations of 0,5; 1,0; 2,0 and 4,0 wt.% of calcium ions to the binder were chosen to observe the effect. The selected compounds were calcium oxide (CaO), calcium hydroxide (Ca(OH)2), calcium formate (CF), calcium nitrate tetrahydrate (CN) and calcium chloride (CC). Calorimetric measurements showed that the optimum water to binder ratio was 0.4. Due to the lower workability, no high-performance cement composites were prepared but only pastes of high-performance cement composite. The effect of the added compounds on the silica fume-containing system was evaluated by isothermal calorimetry, with only samples containing CaO or Ca(OH)2 showing a measurable response. The effect of the added compounds on the silica fume containing system was evaluated by isothermal calorimetry. Subsequently, the effect of 4,0 wt.% Ca2+ in the CF, CN and CC forms on the system containing silica fume and 1,0 wt.% Ca2+ in the CaO or Ca(OH)2 form was evaluated using the R3 test. Isothermal calorimetry was also applied to paste samples containing cement and silica fume as a binder system, where a significant effect on the length of the induction period, on the value of the minimum heat flux in the induction period and on the value of the maximum heat flux in the main hydration peak was observed, especially for the compounds CF, CN and CC. The flexural tensile and compressive strengths of the paste samples were determined at 1, 3, 7 and 28 days after the start of hydration. The highest influence on the three-point bending tensile strength was again observed for compounds CF, CN and CC, with samples reaching significantly lower values than the reference (this was probably due to insufficient dissolution of the compounds). A lower influence on the flexural tensile strengths was observed for the oxide and calcium hydroxide samples. In the case of compressive strengths, there was a significant increase for CF, CN and CC compounds at 0,5 wt.% and 1,0 wt.% Ca2+ concentrations. In the thermal analysis and diffractometry results, a trend of loss of portlandite at the expense of CSH gel was observed for samples containing 4,0 wt.% Ca2+ in compounds CF, CN and CC. Thus, the added compounds probably influenced the kinetics of cement hydration so much that the silica fume had more time for pozzolanic reaction.
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SCC with secondary raw materials
Ťažká, Lucia ; Ťažký, Tomáš (referee) ; Hela, Rudolf (advisor)
Bachelor thesis is focused on the possibility of using secondary raw materials and their application to the production of SCC. Large part deals with impurities of type I and its application results mainly from abroad. Furthermore, this work examines the impact of different types of impurities on the resulting concrete durability in various aggressive environments. The practical part is focused on the use of chemically non-reactive additives of type I instead of the commonly used additives of type II which are used to replace part of cement and the resulting design and manufacture of low-strength SCC using appropriate additives.
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The influence of zinc oxide on the cement composite with silica fume.
Dobiáš, Jiří ; Koutný, Ondřej (referee) ; Šiler, Pavel (advisor)
The aim of this work was to investigate the influence of zinc oxide on the properties of blended Portland cement mixed with silica fume. On the pastes were monitored flow properties and by using of isoperibolic calorimetry process of the hydration. On the prepared samples were studied mechanical properties of obtaining values of compressive and flexural strength after 1, 7 and 28 days. By using of XRD were measured phase composition and microstructure development war observed by SEM. The elemental composition of cement leaches was measured by using of ICP-OES.
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Improving of dispersion of silica fume in high performance concrete
Janča, Martin ; Koutný, Ondřej (referee) ; Šiler, Pavel (advisor)
The goal of this work was to create a method for improving the dispersion of silica fumes for use in high performance concrete. Traditional methods used to design and manufacture high performance concrete emphasize the removal of coarse aggregates. Use of specially sorted fine aggregates at relatively low doses, the use of super-plasticizers and siliceous excrement. The low water content was achieved by using superplasticizer on a polycarboxylate basis. The standard ultrasound technology found in each laboratory was selected for the dispersion of silica fume. For experiments were we used dry silica fume powder and aqueous stabilized suspension. For comparison, were prepared different mixtures which showed the effects of the treatment prior to the use of silica fume.
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Development of high-strength concrete defined properties with the use of secondary raw materials
Ondráček, Michal ; Vítek,, Jan (referee) ; Ďurica,, Tibor (referee) ; Vymazal, Tomáš (referee) ; Hela, Rudolf (advisor)
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.
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Improving of dispersion of silica fume in high performance concrete
Janča, Martin ; Koutný, Ondřej (referee) ; Šiler, Pavel (advisor)
The goal of this work was to create a method for improving the dispersion of silica fumes for use in high performance concrete. Traditional methods used to design and manufacture high performance concrete emphasize the removal of coarse aggregates. Use of specially sorted fine aggregates at relatively low doses, the use of super-plasticizers and siliceous excrement. The low water content was achieved by using superplasticizer on a polycarboxylate basis. The standard ultrasound technology found in each laboratory was selected for the dispersion of silica fume. For experiments were we used dry silica fume powder and aqueous stabilized suspension. For comparison, were prepared different mixtures which showed the effects of the treatment prior to the use of silica fume.
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The influence of zinc oxide on the cement composite with silica fume.
Dobiáš, Jiří ; Koutný, Ondřej (referee) ; Šiler, Pavel (advisor)
The aim of this work was to investigate the influence of zinc oxide on the properties of blended Portland cement mixed with silica fume. On the pastes were monitored flow properties and by using of isoperibolic calorimetry process of the hydration. On the prepared samples were studied mechanical properties of obtaining values of compressive and flexural strength after 1, 7 and 28 days. By using of XRD were measured phase composition and microstructure development war observed by SEM. The elemental composition of cement leaches was measured by using of ICP-OES.
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Development of high-strength concrete defined properties with the use of secondary raw materials
Ondráček, Michal ; Vítek,, Jan (referee) ; Ďurica,, Tibor (referee) ; Vymazal, Tomáš (referee) ; Hela, Rudolf (advisor)
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.
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