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Initiation of stable crack propagation of selected building composites
Majtánová, Romana Viktória ; Veselý, Václav (referee) ; Keršner, Zbyněk (advisor)
The purpose of my bachelor’s thesis is study of the effects of fibres in normal-weight concrete and light-weight concrete. Specimens were prepared from concrete with polypropylene fibres FORTA FERRO of three different lengths – 19, 38 and 54 mm – and also reference concrete (without fibres) was prepared. This thesis contains gradual evaluation of fracture tests on specimens from mentioned materials. The used fracture test was a three–point bending fracture test on beams with a central notch. From the measured load–deflection in the middle of span and load–crack mouth opening displacement diagrams were determined values of modulus of elasticity, unstable fracture toughness, initiation part of fracture toughness and also load level for beginning of stable crack propagation composites. For determination was used „double–K“ fracture model. For illustration is described evaluation using the effective crack model.
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Influence of dispersed reinforcement on the physico-mechanical properties of the resulting composite
Láník, Jaromír ; Adámek, Jiří (referee) ; Kolář,, Karel (referee) ; Doc.Ing. Karel Kubečka, Ph.D (referee) ; Schmid, Pavel (advisor)
The dissertation is focused on the issue of implementation and evaluation of the laboratory tests fiber reinforced concrete. The issue of steel fiber is solved in terms of their physico-mechanical parameters, which are an important part of their design and reliable operation in the product design. The experimental part of the thesis is focused on laboratory tests of steel fiber of different strength classes and different weight benefits of steel fibers, the default reference mixture of plain concrete are certified mixtures commonly used as structural concrete in construction. The evaluation of the testing of samples produced steel fiber is made by three selected recommending regulations for the design and testing of structural steel fiber. In conclusion, the individual obtained experimental results are compared.
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Effect of type and dose of scattered reinforcement on selected properties of concrete.
Láníková, Lucie ; Schmid, Pavel (referee) ; Láník, Jaromír (advisor)
The Master’s thesis is focused on the research influence the dose and type of scattered reinforcement in a reference concrete on physical and mechanical properties of the resulting composite. The investigated properties of composite belongs compressive strength, tensile strength in the flexural and tensile strength in the transverse, static modulus of elasticity in compressive strength, dynamic modulus of elasticity determined using NDT tests. The reference concrete mixture is certified as structural concrete of the class, which is commonly used on construction sites.
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Experimental and numerical analysis of rheological processes during the concrete maturation.
Zvolánek, Lukáš ; Navrátil, Jaroslav (referee) ; Vítek,, Jan (referee) ; Terzijski, Ivailo (advisor)
This doctoral thesis deals with the volume changes of structural concrete caused by its shrinkage. Great importance is given to the evaluation of concrete resistance against shrinkage cracking, too. A lot of physical and numerical experiments were carried out before results and conclusion of observed phenomena was publicized. The amount of physical tests and utilization rate of the experiments can be enlarged and intensified due to the usage of materials made of micro-concrete. Consequently, the design of concrete mixtures with the ordinary size of aggregate particle reflected the large knowledge obtained by micro-concrete. In this work, the effect of different fibres and its different amount was also researched. Finally, the optimized fibre concrete mixture was designed. During the testing, the unique method referred to as “Complex experiment” was developed. Obtained data from the Complex experiment allows predicting when the shrinkage cracks may occur. The final comparison between all tested materials made of concrete was performed by means of unique parameter referred to as “Critical degree of restraint”. It was proofed that the resistance of optimized fibre concrete against to shrinkage cracking is twice of ordinary concrete. Moreover, the shrinkage cracks did not occur in the developed fibre concrete during the observed period. Based on the obtained results the new scaling factors for the rheological model B4 were derived. Due to the new scaling factors, the model B4 describes the real behavior of special composite materials very well.
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Experimental and numerical analysis of rheological processes during the concrete maturation.
Zvolánek, Lukáš ; Navrátil, Jaroslav (referee) ; Vítek,, Jan (referee) ; Terzijski, Ivailo (advisor)
This doctoral thesis deals with the volume changes of structural concrete caused by its shrinkage. Great importance is given to the evaluation of concrete resistance against shrinkage cracking, too. A lot of physical and numerical experiments were carried out before results and conclusion of observed phenomena was publicized. The amount of physical tests and utilization rate of the experiments can be enlarged and intensified due to the usage of materials made of micro-concrete. Consequently, the design of concrete mixtures with the ordinary size of aggregate particle reflected the large knowledge obtained by micro-concrete. In this work, the effect of different fibres and its different amount was also researched. Finally, the optimized fibre concrete mixture was designed. During the testing, the unique method referred to as “Complex experiment” was developed. Obtained data from the Complex experiment allows predicting when the shrinkage cracks may occur. The final comparison between all tested materials made of concrete was performed by means of unique parameter referred to as “Critical degree of restraint”. It was proofed that the resistance of optimized fibre concrete against to shrinkage cracking is twice of ordinary concrete. Moreover, the shrinkage cracks did not occur in the developed fibre concrete during the observed period. Based on the obtained results the new scaling factors for the rheological model B4 were derived. Due to the new scaling factors, the model B4 describes the real behavior of special composite materials very well.
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Influence of dispersed reinforcement on the physico-mechanical properties of the resulting composite
Láník, Jaromír ; Adámek, Jiří (referee) ; Kolář,, Karel (referee) ; Doc.Ing. Karel Kubečka, Ph.D (referee) ; Schmid, Pavel (advisor)
The dissertation is focused on the issue of implementation and evaluation of the laboratory tests fiber reinforced concrete. The issue of steel fiber is solved in terms of their physico-mechanical parameters, which are an important part of their design and reliable operation in the product design. The experimental part of the thesis is focused on laboratory tests of steel fiber of different strength classes and different weight benefits of steel fibers, the default reference mixture of plain concrete are certified mixtures commonly used as structural concrete in construction. The evaluation of the testing of samples produced steel fiber is made by three selected recommending regulations for the design and testing of structural steel fiber. In conclusion, the individual obtained experimental results are compared.
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Properties of concrete with the addition of plasma modified polypropylene fibers
Vorel, Pavel ; Herka, Petr (referee) ; Bodnárová, Lenka (advisor)
Master‘s thesis focuses on concrete combined with polypropylen fibres produced commercially, fibres without surface modifications and fibres modificated by plasma. Most important topic of the thesis is experimental verification of influence of plasma modificated fibres on attributes of fresh concrete and physical-mechanical attributes of solidified concrete. Based on the results of the tests perfomed on examin units compares results and anylyses applicability of different fibre surface modifications.
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Effect of type and dose of scattered reinforcement on selected properties of concrete.
Láníková, Lucie ; Schmid, Pavel (referee) ; Láník, Jaromír (advisor)
The Master’s thesis is focused on the research influence the dose and type of scattered reinforcement in a reference concrete on physical and mechanical properties of the resulting composite. The investigated properties of composite belongs compressive strength, tensile strength in the flexural and tensile strength in the transverse, static modulus of elasticity in compressive strength, dynamic modulus of elasticity determined using NDT tests. The reference concrete mixture is certified as structural concrete of the class, which is commonly used on construction sites.
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Initiation of stable crack propagation of selected building composites
Majtánová, Romana Viktória ; Veselý, Václav (referee) ; Keršner, Zbyněk (advisor)
The purpose of my bachelor’s thesis is study of the effects of fibres in normal-weight concrete and light-weight concrete. Specimens were prepared from concrete with polypropylene fibres FORTA FERRO of three different lengths – 19, 38 and 54 mm – and also reference concrete (without fibres) was prepared. This thesis contains gradual evaluation of fracture tests on specimens from mentioned materials. The used fracture test was a three–point bending fracture test on beams with a central notch. From the measured load–deflection in the middle of span and load–crack mouth opening displacement diagrams were determined values of modulus of elasticity, unstable fracture toughness, initiation part of fracture toughness and also load level for beginning of stable crack propagation composites. For determination was used „double–K“ fracture model. For illustration is described evaluation using the effective crack model.
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Cement composite materials with polypropylene fibers
Preisner, Martin ; Hela, Rudolf (referee) ; Bodnárová, Lenka (advisor)
This thesis deals with summarizing the possible effects of the addition of polypropylene fibers, especially low temperature plasma treated on the properties of cement composites and concrete. They are given basic information and distribution of polypropylene fibers. It describes the finish polypropylene fiber low-temperature plasma. The experimental part focuses on the effect of dispersion of polypropylene fibers treated plasma in the cement matrix.
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