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Influence of dosage of steel fibres on the loss of consistency of fresh concrete and compresive strength of hardened concrete.
Kuře, Václav ; Źalud, Oldřich (referee) ; Vymazal, Tomáš (advisor)
Bachelor work is focused on problems of a consistency of fresh fiber reinforced concrete. The consistency was characterized by a slump test and by a test of spilling how is it described in ČSN EN 12350. Obtained results are compared with a reference sample of a fresh concrete and between themselves. Further the work is focused on volumetric changes during maturation which are integral part of physical properties of the concrete. Influence of a dispersed reinforcement was monitored on the cube strength in plain pressure of individual mixed sample too. Total evaluation of tested parameters is states at the end of the work including comment about possible ways of interference of tests.
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Comparison of selected parameters of tensile strength of concrete
Rozsypalová, Iva ; Žítt, Petr (referee) ; Daněk, Petr (advisor)
The thesis deals with a comparison of the selected strength tension properties of the hardened concrete and finding relationships between them. This is essentially a simple tensile strength, tensile flexural strength and tensile splitting strength. The text describe the testing procedures to determine the tensile strength of concrete. Furthermore, there are presented the results of testing on different types of concrete (plain concrete, lightweight concrete, steel-fiber concrete, polymer-fibre concrete and high strength concrete). The conclusion deals with the derivation of dependancy between concrete strengths and comparing the values obtained from the available relations with the results of the tests.
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Study of influence of input parameters for the numerical modeling of the compression test
Polách, Marek ; Keršner, Zbyněk (referee) ; Lehký, David (advisor)
The thesis analyses influence of input parametres of the 3D Non Linear Cementitious 2 material model for the numerical modeling of compression test performed in ATENA 2D and ATENA 3D software. The aim is to identify parametres with considerable influence and subsequently replicate the load-deflection curve obtained from laboratory compression test by numerical modeling. The effects of selected model and material model settings are studied on three kind of models in total. As tools for analyzing the effects, deterministic and statistic sensitivity analyses were chosen. Parametres with significant influence will be highlighted and added to the group of parametres obtained from numerical modeling of three-point bending test. This will create a set of parametres of considerable influence when it comes to modeling advanced structures with different types of stresses.
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Properties of Fiber Reinforced Plastics
Jastrzembská, Alena ; Petránek, Vít (referee) ; Bodnárová, Lenka (advisor)
This thesis deals with the theoretical part of raw materials, production and properties of composite materials with fiber reinforcement and polymer matrix. It also gives a brief overview of selected prominent Czech and foreign producers of composite materials with polymer matrix and fiber reinforcement. The practical section deals with testing the durability of selected composite profiles immersion in aggressive environments and testing of compressive strength.
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Modification of silicate materials for floors
Šlechtický, Luboš ; Ing. Miroslav Šťenko, Ph.D., LB Cemix (referee) ; Šťastník, Stanislav (advisor)
The thesis is devoted to the issue of flooring materials, cement and plaster. In the first part are discussed general properties and general requirements for flooring, as well as presents the most important properties of selected flooring materials. The work is dedicated to the modulus of elasticity, adhesion to the substrate and strength parameters of the tested materials. It also evaluates the effects of redispersible polymer powders in silicate compositions intended for floors.
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Properties, Testing and use of UHPC in Structures
Myšičková, Lucie ; Kocáb, Dalibor (referee) ; Cikrle, Petr (advisor)
Thesis describes properties and composition of UHPC compared to concretes of normal and high strength. It gives examples of already completed structures made of UHPC. The experimental part describes the optimization of concrete mix and production of specimens. In the end results of testing the properties of the developed mix from tests of dynamic and static modulus of elasticity, compressive strength and tensile strength by bending are described.
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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.
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Influence of Initial Conditions on the Modulus of Elasticity of Concrete for Bridges
Blažek, Michal ; Bílek,, Vlastimil (referee) ; Cikrle, Petr (advisor)
Beside the compressive strength of concrete, which is considered as the basic parameter parameter for design of concrete structures a modulus of the concrete elasticity should be set as well. This thesis deals with influences, which are acting on the concrete, particularly within the initial stage of its hardening (i.e. within 28 days after casting). Nowadays, when time is the most valuable factor, some knowledge is required about mechanical properties of concrete earlier than after above mentioned 28 days and to apply them advantageously. The concrete in initial stage of hardening is influenced by many factors that affect progress of the elasticity modulus during the course of the time. For understanding of these problems a literature search was performed, as well as the experiment demonstrating the effect of temperature on the modulus of the concrete elasticity. The effect of temperature on the modulus of elasticity of concrete in initial stage of hardening has not been intensively studied yet. Therefore, more attention is paid to it by this elaborate. The experiment investigated the static and dynamic elastic modulus of concrete, whose recipe is similar to one used for production of prefabricated and prestressed bridge girders.
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New devices for diagnostics of historical structures
Hasníková, Hana ; Kloiber, Michal ; Zíma, Pavel
The aim of the paper is to present a few new devices that were developed at ITAM AS CR for non-destructive testing of materials, especially those from historically valuable structures. So called microtube is a semi-automatic portable tool for water absorption measurements. It consists of box with microprocessor where the time is recorded and the plastic “pistol” – a part that is in contact with the material surface and where the scaled micro-tube is fixed on. The natural stones, mortars and other porous materials can be measured by the microtube; it is very useful to assess the efficiency of various hydrophobic treatments used within the restoration. The diagnostic device for in-situ assessment of timber in existing structures enables direct determination of conventional compressive strength and modulus of deformability in arbitrary depth along timber profile. The semi-destructive method causes a very gentle damage on the structural members.
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