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Development glass-concrete of with high mechanical properties
Plochý, Ondřej ; Lederer, Peter (referee) ; Hela, Rudolf (advisor)
This master thesis summarizes the current knowledge regarding the design and properties of glass fiber reinforced concrete products. It also deals with the design of a new concrete recipe for Dako spol. s.r.o company. There is verified effect of changes in input materials in real conditions the company to increase tensile bending strength above 20 MPa.In particular, verification of the use of building chemistry like superplasticizing additives, polymer-cement matrix or a change type or dose of glass fiber.
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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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Lightweight concrete with reinforcement
Plochý, Ondřej ; Hubertová,, Michala (referee) ; Hela, Rudolf (advisor)
This bachelor thesis summarizes the current knowledge regarding to the design and properties of lightweight concrete and concrete with reinforcement. Also deals with research of lightweight aggregate concrete with Liapor and its interaction with dispersed steel fibers. The work examined recipes of volume classes D1,6 and D1,8 and strength classes SFRLC 20/22 and SFRLC 25/28. Recipes are monitored by physical-mechanical and rheological properties.
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Verification of actual physical-mechanical parameters of composite material
Jablonská, Markéta ; Žítt, Petr (referee) ; Láník, Jaromír (advisor)
Diploma thesis deals with composite materiál and it is dedicated to steel fiber concreat. The thesis focuses on verification of mechanical parameters of the steel fiber concrete. Especially on the compressive (tensile) strength at first cracking and the compressive strength in cracked state. Testing was conducted on concrete different tensile with 30 kg on m3 steel fibers KrampeHarex DE 50/1,0 N. The thesis is divided into theoretical and experimental part.
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Study of the properties of concrete with reinforcement, intended for the production of concrete egg-shaped tubes
Šťastný, Antonín ; Hela,, Vlastimil (referee) ; Hubáček, Adam (advisor)
This diploma thesis examines the properties of concrete with reinforcement, designed for the production of a concrete egg-shaped tubes . The stress is put on using various types of fiber reinforcements. Theoretical part is divided into 4 subsections. The topic of the first subsection is a concrete in general. Second subsection deals with various technology of production of concrete pipes. The third subsection is focused on description and summary of basic properties of concrete and reinforced concrete tubes. The last subsection deals with standardized procedures for testing concrete. Experimental part of this thesis is divided into two subsection. First subsection deals with design of a reference sample. Six different samples of a concrete were designed and their rheological properties were tested. Second subsection deals with the additi-on of various types of fiber reinforcement to the reference sample. Eight different admixtures of a concrete were added to the reference sample. Properties of these admixtures were tested in fresh and hardened state.
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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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