|
|
Steel-Concrete Columns Composed of High-Strength Materials
Röder, Václav ; Štěpánek, Petr (referee) ; Studnička,, Jiří (referee) ; Vičan,, Josef (referee) ; Karmazínová, Marcela (advisor)
The main objective of this thesis is the verification of the buckling strength of the composite compression members which were made from high-strength materials. This thesis is divided into four main chapters which are interconnected. The first chapter summarizes the current state of the problem of the compression members. The basis of this part is the elementary theories and researches, the task of this text is attempted to understand and obtain normative procedures which are important for practical use. The second part deals with the theoretical analysis of composite column, mainly with the examination of the individual effects on the buckling strength. The result of the first and the second parts is analytical algebraic equations which determine the buckling strength of the member. The third part contains the numerical analysis, which leads to create a numerical model of the compression column. The numerical model is used for the verification of the theoretical analysis and for the investigation of the behaviour of the column loaded by axial force. The last part deals with the experimental verification of the previous analyses. There are tested various types of the composite columns, which were made of steel with a yield strength up to 455 MPa and of the concrete with a cube compression strength up to 102 MPa. Experimental results confirmed the high reliability of centrally loaded column and every tested columns failed by flexural buckling. The final step is evaluation and comparison of the results obtained from previous four parts. It was founded that design criteria for centrally loaded steel-concrete column are too conservative and design relationships doesn´t use the positive properties of high-strength materials for economic design.
|
|
|
High-performance concretes based on the secondary raw materials
Sáček, Josef ; Brandštetr, Jiří (referee) ; Šoukal, František (advisor)
This work is devoted to study of physical-mechanical properties and structure of high performance concretes (HPC) based on portland cement. The attention is focused on possibility of substitution of economic high-cost components of concrete with utilization of secondary raw materials or cheaper components. Properties of raw materials and their influence on whole quality of concrete were tracked by various methods. Mechanical properties of prepared HPC samples were tested especially (compression and flexural strength) with further microscopic study of structure. Isoperibolic calorimetry and X-ray powder diffraction method were also used for concrete characterisation. These methods allowed to determine the influence of raw materials on prepared HPC and to carry out a certain optimization among price and quality of this material.
|
|
|
Development and testing of high performance concrete for subtle structures
Myšičková, Lucie ; Cikrle, Petr (referee) ; Bílek, Vlastimil (advisor)
Thesis describes properties of HPC compared to concretes of normal and high strength. It further describes the input materials and the procedure for designing the composition of the mixture. It gives examples of already completed structures made of HPC. The experimental part describes the optimization of concrete mix and production of specimens. In the end results of testing the properties of the developed mixes from tests of dynamic and static modulus of elasticity, compressive strength and tensile strength by bending are described.
|
|
|
The Study of Aditives and Admixture Influence on High-Performance Concrete Properties
Šiler, Pavel ; Bílek, Vlastimil (referee) ; Brandštetr, Jiří (referee) ; Havlica, Jaromír (advisor)
The aim of this work was to develop the method for the determination of the superperplasticizers (SP) content in the water solution. The method developed was then applied to study the SP adsorption on the individual components used for high-performance concrete and the influence of the temperature and pH values over this adsorption. Furthermore the influence of the water to binder ratio, SP, finely grounded granulated blast furnace slag, fly ash, silica fume, finely ground silica sand and bauxite on the hydration process was studied by means of isoperibolic, isothermal and solution calorimetry. The compressive and flexural strength of most samples used in calorimetric experiments was also determined.
|
|
|
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.
|
|
|
Improving of dispersion of silica fume in high performance concrete
Janča, Martin ; Koutný, Ondřej (referee) ; Šiler, Pavel (advisor)
The goal of this work was to create a method for improving the dispersion of silica fumes for use in high performance concrete. Traditional methods used to design and manufacture high performance concrete emphasize the removal of coarse aggregates. Use of specially sorted fine aggregates at relatively low doses, the use of super-plasticizers and siliceous excrement. The low water content was achieved by using superplasticizer on a polycarboxylate basis. The standard ultrasound technology found in each laboratory was selected for the dispersion of silica fume. For experiments were we used dry silica fume powder and aqueous stabilized suspension. For comparison, were prepared different mixtures which showed the effects of the treatment prior to the use of silica fume.
|
|
|
The influence of aggregate on the properties of high performance concrete.
Bezděk, Ondřej ; Krátký, Josef (referee) ; Šiler, Pavel (advisor)
This bachelor thesis is focused on the influence of aggregates on the mechanical properties of high-performance concrete. The flexural strenght and the compressive strenght were observed after 1, 7 and 28 days. The process of hydratation was monitored using isoperibolic calorimetry. Laser particle size analysis of aggregates was also performed. As materials were used: Portland cement CEM I 42,5 R-Sc Mokrá, finelly ground silica sand, calcinated bauxite, fine test sand ČSN EN 196-1, medium test sand ČSN EN 196-1, rough test sand ČSN EN 196-1 and polycarboxylate superplasticizer Glenium Ace 40.
|
|
|
ultra-high-strength concretes
Ambruz, Pavel ; Hubáček,, Adam (referee) ; Hela, Rudolf (advisor)
Thesis deals with summarizing knowledge about production methods of ultra – high – strength concrete (UHSC) and their possible use in practice, which is documented on the existing building. Further work shows suitable raw materials for production UHSC and their availability on the Czech market. The practical part results an experiment whose outcome should be concrete with a compressive strength of 150 MPa.
|
|
|
Reactive powder concretes (RPC) with polymer latexes
Petrů, Ludmila ; Koplík, Jan (referee) ; Šoukal, František (advisor)
This thesis deals with the effect of polymeric latexes on the properties of concrete based on reactive powders. Three types of commercial latexes were used for the preparation of the samples, namely Revacryl, Duvilax and Plextol. Revacryl AE 2091 is an aqueous dispersion of styrene-acrylate copolymer with a high content of solids. Duvilax BD-20 is a homopolymer polyvinyl acetate dispersion that does not contain fillers with plasticizers. Plextol X 4002 is an aqueous, self-setting acrylic emulsion with a high content of solids. These latexes were added to the samples at concentrations of 0,20; 0,40; 0,60; 1,20 and 2,50 %. To determine the effect of latex on processability, the flow rate of the fresh mixture was measured. The main objective was to determine the ballistic resistance of modified concretes based on reactive powders. The DOP test was used for the determination. Furthermore, the change in mechanical properties was determined by adding a polymer to concrete based on reactive powders. The improvement in properties is expected to be due to the formation of a polymer film and a polymer-cement co-matrix. To demonstrate the film formation, the microstructure of the samples was observed by a raster electron microscope.
|
|
|
Improving of dispersion of silica fume in high performance concrete
Janča, Martin ; Koutný, Ondřej (referee) ; Šiler, Pavel (advisor)
The goal of this work was to create a method for improving the dispersion of silica fumes for use in high performance concrete. Traditional methods used to design and manufacture high performance concrete emphasize the removal of coarse aggregates. Use of specially sorted fine aggregates at relatively low doses, the use of super-plasticizers and siliceous excrement. The low water content was achieved by using superplasticizer on a polycarboxylate basis. The standard ultrasound technology found in each laboratory was selected for the dispersion of silica fume. For experiments were we used dry silica fume powder and aqueous stabilized suspension. For comparison, were prepared different mixtures which showed the effects of the treatment prior to the use of silica fume.
|
guest ::
