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The use of micro and nanotechnology to develop ultra high strength and high performance concrete with special features
Vlč, Viktor ; Ťažký, Tomáš (referee) ; Hela, Rudolf (advisor)
The use of nanotechnology has become wide spread in all branches of science. Nanotechnology help us to understand microstructure and due to the world has started to produce new materials. One of many examples carbon nanotubes (CNTs). In diploma thesis I tried to find the way of successful introduction into concrete mixture. I was studying influence of CNTs and other nano particles and I was comparing them with referential samples (without CNTs). Also I tested the improvement of mechanical characteristics of concrete. The morphology of nano particles was studied using Scanning Electron Microscopy (SEM). The results show that introduction of nanoparticles to results in increasing strength and higher density. That is why High Performace Concrete so resistant and durable.
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Study of dispersion of carbon nanotubes in cement composites
Michnová, Kamila ; Hela, Rudolf (referee) ; Bodnárová, Lenka (advisor)
Carbon nanotubes have the ability to improve the mechanical and physical properties of cement composites. However, their introduction into industrial utilization is hampered by several obstacles. It primarily involves the effective incorporation into the cement matrix, health and ecological risks. The experimental part of the work deals with the dispersing carbon nanotubes in aqueous solution and their subsequent integration into the structure of the cement matrix.
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The development of self-compacting concrete with fast runs of strength and elasticity modulus
Skřivánek, Michal ; Hela,, Vlastimil (referee) ; Hela, Rudolf (advisor)
My bachelor thesis is about a development of self-compacting concrete. The main advantage of this method is a shorter duration of producing strength concrete and also modulus of elasticity. My analysis consists of describing self-compacting concrete properties, methods for speeding up the process of building strength concrete from less effective heating to using advanced concrete admixtures. Further, an important chapter about influence of concrete mixture composition on modulus of elasticity measurements and in-depth analysis of the SCC mixture composition. Theoretical part is ended by a summary of SCC properties in a fresh or hardened state – all experiment specifics are included. In order to deliver a shorter duration of producing strength concrete and modulus of elasticity in early stages of curing, every SCC mixture mentioned in practical part have been carefully created based on achieved theoretical knowledge with a goal to minimize the impact on rheology of concrete mixture.
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Study of the influence of feedstock composition and the values of the modulus of elasticity of concrete
Šafrata, Pavel ; Křížová, Klára (referee) ; Hela, Rudolf (advisor)
Modulus of elasticity is significantly reflected feature of concrete, besides the compressive strength in static design nowadays. Low modulus of elasticity can cause unacceptable deflections for subtle skeletal structures. It is at least irresposible to count with empirical formulas since there is a wide range of materials and additives in production of concrete. The aim of this thesis is to study the influence of large fraction aggregate on static and dynamic modulus of elasticity of concrete and recommendation for appropriate measures to produce concrete with high modulus of elasticity. The experimental part is further following up the influence of air content in concrete on the modulus of elasticity.
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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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Study the possibility of using recycled aggregate concrete for the manufacture of structural concrete
Skriňáková, Eva ; Stehlík, Dušan (referee) ; Hela, Rudolf (advisor)
This bachelor's thesis is aimed on the issues of using aggregate from recycled concrete rubble. The introduction describes the possibilities of concrete recycling and methods for fresh and hardened composite recycling. Next mentioned are physical and mechanical properties of recycled aggregate reused in concrete and comparison with natural aggregate concrete. Last part of theoretical section presents the opportunities of using recycled concrete to sub-base layers and concrete pavements. The practical section is focused on the application of recycled concrete aggregate to design concrete mixture of required strength class and verifying the possibility of usage in the exposure class XF3 and also design hydraulically bound course. The results of the practical section is to determine the suitability of recycled concrete usage for concept mentioned above.
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