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Possibilities of clay plasters shrinkage elimination
Melichar, Jindřich ; Koplík, Jan (referee) ; Opravil, Tomáš (advisor)
Earth plasters which are applicated in interiers don´t have just an estetic, but mainly heat storage function. To accomplish better storage properties the plaster has to be laid on the wall in sufficient thick ply. But this use to be accompained by creating of cracks during dehydration of the plaster. This bachelor work will be considering possibilities of elliminating this negative event by additing suitable components to suppress shrinkage and cracks by creating ettringite.
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Gel infusion screen system for additional waterproofing of various types of masonry with share of secondary raw materials
Melichar, Jindřich ; Klečka,, Tomáš (referee) ; Dohnálek,, Pavel (referee) ; Novotný, Miloslav (referee) ; Drochytka, Rostislav (advisor)
Virtually any construction project in our climate zone is facing some form of moisture. Older and historical buildings are mostly affected by the negative impact of water. Previously, the additional reduction of the moisture was executed only by mechanical methods, pushing insulating sheets or breaking through and cutting of masonry. Over time chemical methods were also invented, which are compared to the mechanical considerably simpler and user friendly applications to statics of treated buildings, making them ideal for the treatment of historical buildings or buildings that would not bear significant disruption. The main principle of chemical methods of redevelopment of wet masonry is the application of special material into the line of drilled holes with a given pitch. Subsequent penetration of the grouting material is believed to intersect an arc of individual drill holes, and thus to create so-called grout curtain that prevents the accumulation of water above it. Injection material may also contain a proportion of secondary raw materials, thereby reducing the influence of the impact of production on the environment. Efficiency infusion materials in masonry affected by many factors, such as temperature, humidity, or the type of material treated. It is also an important factor to determine the effectiveness of the remediation of the material, proving its ability to penetrate the building material by identifying its presence in it.
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New possibilities of using superabsorbent polymers in cement composites
Holubová, Petra ; Melichar, Jindřich (referee) ; Černý, Vít (advisor)
The work deals with the influence of superabsorbent polymers (SAP) on the structure and properties of cement composites. SAPs excel in their unique ability to hold large amounts of water. This property can be used in hydration processes for internal curing of concrete. Two types of mixtures were tested in cement paste, which were further modified by two types of SAP. SAPs were always used in two dosing modes (dry, in suspension). The samples were then stored for 28 days in a laboratory conditions, respectively. in an conditions with a temperature of 30 °C. Physical and mechanical properties, such as compressive strength, flexural tensile strength and bulk density, were determined. The addition of SAP to the mixture resulted in an increase in tensile strength of almost twofold. It can therefore be concluded that SAP helped with hydration processes.
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Study of the influence of fillers and external conditions on the resistivity of cement composites
Kejda, Dalibor ; Melichar, Jindřich (referee) ; Černý, Vít (advisor)
The progress of new materials is important for the construction industry. Modern materials include cement composites with reduced resistivity. This is achieved by adding suitable electrically conductive fillers. If there is enough of these fillers, the so-called percolation threshold occurs. Suitable fillers (Condufit C4 and Supragraphite C300) have been proposed. Recipes have been designed to be before and after the percolation threshold. The tests were performed on beams measuring 40x40x160 mm with built-in electrodes for measuring their resistivity. The aim of the work was the research of influencing external conditions on cement composites. The effect of temperature was verified. The lowest values of resistivity were evaluated at temperatures of 50 ° C and the resistivity increased with decreasing temperature. The effect of humidity on the resistivity was then verified. Reference samples and samples with a smaller proportion of graphite powder showed larger differences in resistivities with increasing humidity. The samples above the percolation threshold were not much affected by increasing humidity. Finally, the effect of loading on the resistivity of the samples was verified. Almost all samples with increasing compressive stress showed an increasing value of resistivity.
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The optimalization of clay building components
Melichar, Jindřich ; Šiler, Pavel (referee) ; Opravil, Tomáš (advisor)
Clay building components are nowadays one of the most used building materials in the world. Except easy availability and processability clay building components have also heat storage function. This master´s thesis will be considering possibilities of improving thermal and mechanic properties of these materils by additing suitable reinforcements.
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Possibilities of screed application on oily or wet concrete
Holomčík, Zdeněk ; Melichar, Jindřich (referee) ; Drochytka, Rostislav (advisor)
This thesis studiest he track floor system, the interaction of adhesive bonding compound with a underlaying concrete, which will be contaminated by moisture and oil. For such contaminated surface was designed polymer-cement concrete, which were subsequently tested its properties, in order to determine whether it achieves the required strength of 80 MPa uniaxial compressive and whether it can be applied to wet or oily underlaying concrete. From the results we can say that the newly proposed system achieves the specified requirements and could be applied to damp and oily surfaces.
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Development of materials for 3D printing of elements meeting the requirements of transport structures
Romanová, Dorota ; Melichar, Jindřich (referee) ; Žižková, Nikol (advisor)
This bachelor thesis deals with the use of supplementary cementitious materials as a partial replacement of Portland cement in cement composites, focusing on the requirements of transport constructions. The theoretical part consists of a description of the input raw materials as well as cement substitutes, the studied properties of the 3D printed mixtures and a description of the characteristics of the technology. The practical part is focused on the experimental testing of the selected properties with monitoring of the influence of polymer and bio-polymer additive dosage in the proposed formulations and subsequent analysis of the most convenient one for 3D printing.
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Study of the influence of fillers and external conditions on the resistivity of cement composites
Kejda, Dalibor ; Melichar, Jindřich (referee) ; Černý, Vít (advisor)
The progress of new materials is important for the construction industry. Modern materials include cement composites with reduced resistivity. This is achieved by adding suitable electrically conductive fillers. If there is enough of these fillers, the so-called percolation threshold occurs. Suitable fillers (Condufit C4 and Supragraphite C300) have been proposed. Recipes have been designed to be before and after the percolation threshold. The tests were performed on beams measuring 40x40x160 mm with built-in electrodes for measuring their resistivity. The aim of the work was the research of influencing external conditions on cement composites. The effect of temperature was verified. The lowest values of resistivity were evaluated at temperatures of 50 ° C and the resistivity increased with decreasing temperature. The effect of humidity on the resistivity was then verified. Reference samples and samples with a smaller proportion of graphite powder showed larger differences in resistivities with increasing humidity. The samples above the percolation threshold were not much affected by increasing humidity. Finally, the effect of loading on the resistivity of the samples was verified. Almost all samples with increasing compressive stress showed an increasing value of resistivity.
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New possibilities of using superabsorbent polymers in cement composites
Holubová, Petra ; Melichar, Jindřich (referee) ; Černý, Vít (advisor)
The work deals with the influence of superabsorbent polymers (SAP) on the structure and properties of cement composites. SAPs excel in their unique ability to hold large amounts of water. This property can be used in hydration processes for internal curing of concrete. Two types of mixtures were tested in cement paste, which were further modified by two types of SAP. SAPs were always used in two dosing modes (dry, in suspension). The samples were then stored for 28 days in a laboratory conditions, respectively. in an conditions with a temperature of 30 °C. Physical and mechanical properties, such as compressive strength, flexural tensile strength and bulk density, were determined. The addition of SAP to the mixture resulted in an increase in tensile strength of almost twofold. It can therefore be concluded that SAP helped with hydration processes.
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Gel infusion screen system for additional waterproofing of various types of masonry with share of secondary raw materials
Melichar, Jindřich ; Klečka,, Tomáš (referee) ; Dohnálek,, Pavel (referee) ; Novotný, Miloslav (referee) ; Drochytka, Rostislav (advisor)
Virtually any construction project in our climate zone is facing some form of moisture. Older and historical buildings are mostly affected by the negative impact of water. Previously, the additional reduction of the moisture was executed only by mechanical methods, pushing insulating sheets or breaking through and cutting of masonry. Over time chemical methods were also invented, which are compared to the mechanical considerably simpler and user friendly applications to statics of treated buildings, making them ideal for the treatment of historical buildings or buildings that would not bear significant disruption. The main principle of chemical methods of redevelopment of wet masonry is the application of special material into the line of drilled holes with a given pitch. Subsequent penetration of the grouting material is believed to intersect an arc of individual drill holes, and thus to create so-called grout curtain that prevents the accumulation of water above it. Injection material may also contain a proportion of secondary raw materials, thereby reducing the influence of the impact of production on the environment. Efficiency infusion materials in masonry affected by many factors, such as temperature, humidity, or the type of material treated. It is also an important factor to determine the effectiveness of the remediation of the material, proving its ability to penetrate the building material by identifying its presence in it.
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