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Optimization of the concrete composition with the use of recycled concrete aggregates
Skriňáková, Eva ; Holák, Michal (referee) ; Hela, Rudolf (advisor)
Concrete as a building material is subject to continuous innovation and thanks to advanced technology and quantum of research, its properties are still improved. It is logical that the more concrete we produce, the more waste it arises. The volume of this waste can not be stored in landfills endlessly, nowadays most of the waste economies in the world are trying to recycle concrete rubble. The recycling is not such a problem, the technology has been long verified but the quality of the recycled concrete aggregate is unquestionably one of the primary assumption which leads to accomplish required properties of concrete. In fact, the recycling process is „crushing“ the concrete into particles with an effort to eliminate the cement paste on the surface of the aggregate. An ideal solution would be create a resistant and firm coating that would adhere perfectly to the cement matrix. This diploma thesis is focused on the properties of recycled concrete aggregate and methods of improvement and optimization of the concrete mix composition.
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Research of effective use and activation of activ concrete additions
Mikhailova, Olesia ; Ťažký, Tomáš (referee) ; Hela, Rudolf (advisor)
The theoretical part describes the admixtures that are used in cement replacement. Here also summarizes the findings on the influence of granulomentry, grain shape and fineness of admixtures on the density of the cement matrix. The practical part is experimentally verified the influence of fineness admixtures and grain size on the mechanical properties of concrete. Also, the rheological properties of cement are compared with admixtures depending on the type and dosage and time.
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Study of the effect of selected types of aditives on the properties of cement composites
Kavka, Lukáš ; Ťažký, Tomáš (referee) ; Bodnárová, Lenka (advisor)
The diploma thesis describes admixtures for concrete. It deals with the influence of admixtures on the properties of cement composites in the fresh and hardened state. The theoretical part described the individual components of concrete, where the main attention was focused to inert admixtures and their effect on mechanical properties, shrinkage, resistance of cement composites to aggressive medium. Furthermore, the effect of admixtures on concretes with recycled aggregates was described. In the first stage of the practical part, cement mortars with 25, 35 and 50% replacement of cement admixtures were created. In the second stage, concretes with admixtures and a minimum strength class of C30/37 and C50/60 were created. Finely ground granulated slag, micronized limestone and granite stone dust were used as admixtures in mortars and concretes. The change of properties in the fresh and hardened state was observed on cement composites.
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Studying the properties of high strength concrete using micro and nano admixtures
Gabko, Miroslav ; Bodnárová, Lenka (referee) ; Hela, Rudolf (advisor)
The objective of this bachelor thesis is to examine the properties of high strength concretes with the main focus on application of mikro or nano admixtures. In theoretical part their production, the properties and the influence on fresh and hardened properties of cement composites are described. In addition, it explores the influence of plasticizer type, some properties of aggregate and cement types. The practical part focuses on testing cement mortars in which fine cements were added. The compressive and flexural strengths were examined after 7 and 28 days of curing, moreover, rheological properties and heat hydration of cements were also observed. Furthermore, the influence of high speed mixing on cement mortars properties was studied.
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Effect of active ingredients to the activity of cementing compound with non-alkaline accelerator additive for sprayed concrete.
Závacký, Jakub ; Hela,, Vlastimil (referee) ; Hela, Rudolf (advisor)
The bachelor thesis deals with the problems of the sprayed concrete with the focus on usage of the active ingredients with non-alkaline accelerator additive. The theoretical part covers the current level of knowledge of how the active ingredients are used in the sprayed concrete and their influence on the process of hydration. In the experimental part the reactivity of cementing compound with non-alkaline accelerator on the basis of aluminium sulphate were compared in a laboratory when the active ingredients (such as slag, fly-ash and very fine limestone) were used. The cements CEM I 42,5 R, made by different producers were verified on the basis of the setting time and early strength gain using the Vicat needle to examine the mechanical properties after 6 and 24 hours.
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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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Study of the effect of selected types of aditives on the properties of cement composites
Kavka, Lukáš ; Ťažký, Tomáš (referee) ; Bodnárová, Lenka (advisor)
The diploma thesis describes admixtures for concrete. It deals with the influence of admixtures on the properties of cement composites in the fresh and hardened state. The theoretical part described the individual components of concrete, where the main attention was focused to inert admixtures and their effect on mechanical properties, shrinkage, resistance of cement composites to aggressive medium. Furthermore, the effect of admixtures on concretes with recycled aggregates was described. In the first stage of the practical part, cement mortars with 25, 35 and 50% replacement of cement admixtures were created. In the second stage, concretes with admixtures and a minimum strength class of C30/37 and C50/60 were created. Finely ground granulated slag, micronized limestone and granite stone dust were used as admixtures in mortars and concretes. The change of properties in the fresh and hardened state was observed on cement composites.
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Effect of active ingredients to the activity of cementing compound with non-alkaline accelerator additive for sprayed concrete.
Závacký, Jakub ; Hela,, Vlastimil (referee) ; Hela, Rudolf (advisor)
The bachelor thesis deals with the problems of the sprayed concrete with the focus on usage of the active ingredients with non-alkaline accelerator additive. The theoretical part covers the current level of knowledge of how the active ingredients are used in the sprayed concrete and their influence on the process of hydration. In the experimental part the reactivity of cementing compound with non-alkaline accelerator on the basis of aluminium sulphate were compared in a laboratory when the active ingredients (such as slag, fly-ash and very fine limestone) were used. The cements CEM I 42,5 R, made by different producers were verified on the basis of the setting time and early strength gain using the Vicat needle to examine the mechanical properties after 6 and 24 hours.
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