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The Methodology for Testing the Bond Between FRP Reinforcement and Concrete Under the Influence of High Temperatures and Fire
Zlámalová, Pavlína ; Zlámal, Martin ; Čairović, Đorđe ; Lagiň, Juraj ; Vašátko, David ; Štěpánek, Petr
The determination and understanding of the bond strength between FRP reinforcement and concrete, which ensures the mutual interaction of these materials, are indispensable for the proper, safe, and reliable design of concrete structures with internal reinforcement. This characteristic also serves as a fundamental parameter for designing the anchorage length of the reinforcement.
While it is one of the fundamental characteristics, there is no domestic or international standards defining the procedure for testing and determining the influence of high temperatures and fire on the bond strength between FRP reinforcement and concrete.
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Utilization of Diffusive Techniques in Study on Reactivity of Biocolloids
Kalina, Michal ; Maršálek, Roman (referee) ; Mráček, Aleš (referee) ; Klučáková, Martina (advisor)
The main aim of this thesis is the utilization of simple diffusion techniques for the study on transport properties of copper ions in the systems containing humic acids with respect to the other parameters, which can affect the process (the structure of diffusion environment, the interactions between transported specie and diffusion matrices, selective blocking of binding sites of humic acids). The first part of experimental works was focused on characterization of studied materials (humic acids, humic sol and humic hydrogel). The main part of the thesis was dealing with the optimization of simple diffusion techniques, which were suitable for the study on transport of copper ions in matrices containing humic acids, taking into account the mutual interactions between studied components in the system. The obtained diffusion characteristics were compared to the data determined using sorption experiments. Consequently, the minor goal of the experimental works of this thesis was also the assessment of the influence of basic physico-chemical parameters of studied materials on transport phenomenon.
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Structural Properties of Ultralight Concrete and its Optimal Application in Structures
Kadlec, Jaroslav ; Bílek,, Vlastimil (referee) ; Adámek, Jiří (referee) ; Terzijski, Ivailo (advisor)
This doctoral thesis deals with design of three variants of ultra lightweight concrete (ULC) and their mechanical properties. The ULC usually has the dry density of 900-1200 kg/m3 and it is possible to use it for load bearing structures. Low density of ULC is achieved by replacing heavy aggregate for lightweight aggregate. The lightweight aggregate is known under the trade name Liapor in the Czech Republic. To achieve density below 1000 kg/m3, an aeration of the paste has to be done. An exchange of heavy aggregate for lightweight aggregate results in a very fragile behavior of ULC. A great attention is paid to bond strength between concrete and reinforcing steel in the thesis. In addition to the standard test of bond strength testing by pull-out, a modified pull-out test is designed, which includes the effect of minimum reinforcement cover. The mentioned test more precisely simulates a real behaviour of the structure exposed to bending moment. The doctoral thesis tries to point out on different parameters between measured data and the applicable standard for the design of load-bearing structures.
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Structural Properties of Ultralight Concrete and its Optimal Application in Structures
Kadlec, Jaroslav ; Bílek,, Vlastimil (referee) ; Adámek, Jiří (referee) ; Terzijski, Ivailo (advisor)
This doctoral thesis deals with design of three variants of ultra lightweight concrete (ULC) and their mechanical properties. The ULC usually has the dry density of 900-1200 kg/m3 and it is possible to use it for load bearing structures. Low density of ULC is achieved by replacing heavy aggregate for lightweight aggregate. The lightweight aggregate is known under the trade name Liapor in the Czech Republic. To achieve density below 1000 kg/m3, an aeration of the paste has to be done. An exchange of heavy aggregate for lightweight aggregate results in a very fragile behavior of ULC. A great attention is paid to bond strength between concrete and reinforcing steel in the thesis. In addition to the standard test of bond strength testing by pull-out, a modified pull-out test is designed, which includes the effect of minimum reinforcement cover. The mentioned test more precisely simulates a real behaviour of the structure exposed to bending moment. The doctoral thesis tries to point out on different parameters between measured data and the applicable standard for the design of load-bearing structures.
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Utilization of Diffusive Techniques in Study on Reactivity of Biocolloids
Kalina, Michal ; Maršálek, Roman (referee) ; Mráček, Aleš (referee) ; Klučáková, Martina (advisor)
The main aim of this thesis is the utilization of simple diffusion techniques for the study on transport properties of copper ions in the systems containing humic acids with respect to the other parameters, which can affect the process (the structure of diffusion environment, the interactions between transported specie and diffusion matrices, selective blocking of binding sites of humic acids). The first part of experimental works was focused on characterization of studied materials (humic acids, humic sol and humic hydrogel). The main part of the thesis was dealing with the optimization of simple diffusion techniques, which were suitable for the study on transport of copper ions in matrices containing humic acids, taking into account the mutual interactions between studied components in the system. The obtained diffusion characteristics were compared to the data determined using sorption experiments. Consequently, the minor goal of the experimental works of this thesis was also the assessment of the influence of basic physico-chemical parameters of studied materials on transport phenomenon.
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Boronized stainless steel with zirconia coatings
Brožek, Vlastimil ; Kolísko, J. ; Kubatík, Tomáš František ; Mastný, L. ; Pokorný, P. ; Tej, P.
Conditions of boronizing are described using a reactive diffusion method of boron from boron carbide and lanthanum hexaboride so that the formation of Fe2B is preferred to FeB which is more brittle and whose structure does not satisfy the conditions for perfect adhesion of modified zirconia ceramics. Perfectly rigid adhesive connection of needle-like embedded interlayers Fe2B in steel AISI 303 prepared by reactive diffusion of a boronizing medium without activators at 1000 ° C and exposure of 2-4 hours has the value of 20 - 24 MPa at the Pinn-off test.Ceramic coatings from Al2O3-ZrO2 ceramics formed on those interlayers have the value of bond strength up to 14 - 20 MPa.Thermal cycling between 100°C - 600 °C confirmed good adhesion of coatings with the underlying steel.During thermal cycling at elevated temperatures (600-1000 °C) there occurs a statistically significant number of faults in cohesion and mechanical destruction of the coatings. One of the reasons are secondary changes
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Plasma coatings of phosphated steels II
Pokorný, P. ; Mastný, L. ; Brožek, Vlastimil
This article follows the introductory part, presented at the conference APROCHEM 2012 and evaluates the possibility of using different kind of phosphate coatings for the pretreatment of mild steel intended for plasma sprayed ceramic coatings. The phosphate conversion coating has to improve the corrosion resistance of coated steel and also to improve and extend the adhesion of ceramic coating to mild steel surface. Selection the most appropriate phosphate coating (zinc, zinc-calcium, manganese and „three-cations“ phosphate) was established to study the dehydration curves by means of DTA and TGA analysis with subsequent analysis of morphology, integrity and composition of the coating after each dehydration section.Samples were exposed at 200 °C for 10 hours.The measurement results showed that the most stable is manganese phosphate. Plasma deposition of corundum was carried out low-temperature plasma generator WSP ®. The corrosion resistance of coated samples with different phosphate
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