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High-grade concrete using nanoparticles
Labaj, Martin ; Bodnárová, Lenka (referee) ; Hela, Rudolf (advisor)
The aim of this paper is to summarize and assess the possibility of using nanoparticles as additives in high performance concrete. These particles have the ability to improve the mechanical and physical properties of cement composites or even gave them brand new ones. Industrial use, however, is hampered by several obstacles. In particular, it is the task of effective incorporation of nanoparticles into the matrix, the health and environmental risks and, last but not least, the financial costs. The experimental part of the work deals with the first-mentioned problem, namely with dispersing carbon nanotubes in aqueous solution and their subsequent integration into the structure of cement mortar.
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Essays on the impact of technological change on economic structure
Pleticha, Petr ; Srholec, Martin (advisor) ; Bajgar, Matěj (referee) ; Goedhuys, Micheline (referee) ; Lábaj, Martin (referee)
Interní Essays on the Impact of Technological Change on Economic Structure Abstract This dissertation investigates the interplay between technological change and economic structure. Welcomed technological change sometimes brings changes to the structure of the economy which introduces not so welcomed economic frictions. On the other hand, economic structure can foster or hinder technological change. This thesis focuses mainly on structural changes such as R&D financing and global value chain (GVC) integration potentially translating into economic productivity. In Chapter 2, I show that business R&D spending exerts both direct and indirect positive effects on value added. Nevertheless, the heterogeneity of the returns to R&D has seldom been examined. Using detailed sectoral data from Czechia over the period 1995-2015, this study finds that privately funded business R&D has both direct and spillover effects, but that the publicly funded part of business R&D only leads to spillovers. The results further suggest that both upstream and downstream spillovers matter, regardless of the source of funding, and that during the period studied, R&D returns were heavily affected by the economic crisis. Lastly, private R&D offers significant returns only after reaching a critical mass, while the effects of public R&D...
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Concretes with high temperature fly ash activated by nanoparticles.
Labaj, Martin ; Bodnárová, Lenka (referee) ; Hela, Rudolf (advisor)
The aim of this thesis is to summarize the knowledge regarding reduction of negative impact of high volumes of fly ash in HVFA concretes using nanotechnology and experimentally verify the findings. To compensate the inferior early-age properties, it is possible to use active nanoparticles, such as nanosilica or nanolimestone. The first step of the experiment was the production of stable nanoparticle’s dispersions using ultrasonic homogenization and UV/Vis spectroscopy. In subsequent steps the influence of nanoparticle’s presence on cementitious materials’ properties was verified on cement pastes and mortars with 40 a 60 % of fly ash. The best variant was then used to produce nano-modified HVFA concretes. Even at a minimum dose, the positive effect on early-age properties indicates the usefulness of nanoparticles in technology of concrete. An important contribution of this thesis is also the acquired knowledge related to the nanoparticle’s behavior and handling.
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High-grade concrete using nanoparticles
Labaj, Martin ; Bodnárová, Lenka (referee) ; Hela, Rudolf (advisor)
The aim of this paper is to summarize and assess the possibility of using nanoparticles as additives in high performance concrete. These particles have the ability to improve the mechanical and physical properties of cement composites or even gave them brand new ones. Industrial use, however, is hampered by several obstacles. In particular, it is the task of effective incorporation of nanoparticles into the matrix, the health and environmental risks and, last but not least, the financial costs. The experimental part of the work deals with the first-mentioned problem, namely with dispersing carbon nanotubes in aqueous solution and their subsequent integration into the structure of cement mortar.
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