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Study of shrinkage reducing admixture efficiency in alkali activated systems
Fojtík, Ondřej ; Koplík, Jan (referee) ; Bílek, Vlastimil (advisor)
Significant drying shrinkage is one of the major issues for the wider application of materials based on alkali-activated slag (AAS). Some shrinkage reducing admixtures (SRA) were developed for the ordinary portland cement systems. A couple of previous studies focused on the efficiency of these SRA in alkali-activated materials. The studies were mainly concentrated on the SRA based on polypropylene glycol. This thesis deals with efficiency of the SRA based on 2 methyl-2,4-pentanediol in AAS pastes and mortars. Influence of the SRA and activator (waterglass) dose on the drying shrinkage and other properties of AAS (flexural and compressive strength, autogenous shrinkage, workability, setting time and microstructure) were investigated. It was found, that at the activator dose when Na2O/slag mass ratio equals 4 or 6 %, SRA causes retardation of hydration, which leads to shrinkage reduction, however strength is reduced significantly, weight lost during the drying is increased and the coarsening of the pore structure occurs. At the activator dose when Na2O/slag mass ratio reaches 8, 10 or 12 %, in the presence of SRA the drying shrinkage is reduced, weight lost during the drying is similar to the reference, strength is increased and microstructure is unchanged against reference. It has been proved that SRA works properly in AAS only at higher activator doses.
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Bigots Curve for the Determination of Plastic Body Properties
Suk, Vojtěch ; Nevřivová, Lenka (referee) ; Sokolář, Radomír (advisor)
This bachelor thesis is focused on the use of the Bigot curve as a tool for assessing the performance of plastic ceramic materials. The theoretical thesis is a form of research of available literature. It elaborates a general view on the Bigot curve and possible application properties which derive from it for some specific soil. In the experimental part were determined properties of plastic ceramic material from location Jirčany from which were formed samples made of plastic dough with different moisture content, with the addition of grog and additives. Properties such as shape of Bigot curve, critical moisture value, size of drying shrinkage and drying sensitivity of the soil were monitored on the samples.
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Review of grease types
Mauer, Jindřich ; Ficza, Ildikó (referee) ; Košťál, David (advisor)
This bachelor thesis provides a basic distribution of greases according various aspects, which are used for lubrication the various components. The first part of bachelor thesis deals with the composition of greases. The following section describes the manufacture of greases. Another section includes the distribution of greases in terms of their composition. The following section is about distribution of greases in terms of practical use. The last part of the bachelor thesis deals with transmission electron microscopy, by this method is possible to examine the structure of greases.
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The possibility of using admixtures for waterroof concrete
Roháček, Lukáš ; Voves, Jiří (referee) ; Hubáček, Adam (advisor)
Bachelor thesis is mainly focused on additions, that have impact on water impermeability and other properities of fresh and hardened concrete. This issue is also described in short section, which is took from foreign reaserch. Thesis further discusses about the standards and regulations that determine, what properties should have waterproof constructions. Experimental part is showing influence of fly ash, slag and silica fume on conzistency, hydratation heat development, strenght, water impermeability, frost resistance and volume changes of the concrete.
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Determination of Vuppor admixture for the refractory light weighting bodies
Svobodová, Markéta ; Keršner, Štěpán (referee) ; Sokolář, Radomír (advisor)
Lightweight refractory products are materials used for the construction of certain parts of industrial furnaces, especially for iron, but also in other sectors where is operated with high temperatures. There are special requests on refractories. The theoretical part contains an overview of used raw materials, production and properties of lightweight refractory products and description of not burnable lightener - chemical additives VUPPOR I and information about previously conducted trials dealing with these topics. The practical part is divided into four parts, which are evaluated by tests which were performed on a refractory clay with chemical additive Vuppor I (samples are lightened and not lightened) - it was primarily a test of sensitivity to drying, density, compressive strength, thermal insulating properties, etc.
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The usability of secondary raw materials in the design of liquefied suspensions based on soil
Hrubý, Jakub ; Kulísek, Karel (referee) ; Černý, Vít (advisor)
The bachelor's thesis deals with the usability of secondary raw materials in the design of liquefied suspensions based on soils in the form of self-compacting grouts. The soil treated in this way can be used as a substitute for backfill material for excavations of engineering networks. The theoretical part deals with the classification and description of soils. Furthermore, the types of soil stabilization using lime, cement, including their liquefaction, are mentioned. A wide range of potentially suitable secondary raw materials and liquefaction mechanization is presented. In the practical part, the basic soil F6-Cl is selected on the basis of a set of available soils. The basic reference mixture consists of soil, lime, cement and liquefier. A proposal for the concept of experimental verification is presented. Part of the concept is the automated calculation of input raw materials. The effect of the action of the superabsorbent polymer and the accelerating additive is verified. Based on optimization selections, functional secondary raw materials are selected. The basic recipe with the optimal amount of accelerating ingredient achieves the best results. Recycled concrete and brick generally improve the resulting parameters. Bed ash achieves the highest strength with the lowest shrinkage.
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Influence of Water-Retentive Admixtures on the Adhesive Strength of Mortars
Žižlavský, Tomáš
The article studies the influence of viscosity-modifying admixtures with water-retentive function on the adherence of natural hydraulic lime-based mortars to traditional fired-clay brick substrate. The substrate was either dried or water-saturated. High water retention value and water/binder ratio led to inferior performance while applied on saturated substrate. On the other hand those properties were found beneficial on the dried substrate. The failure in the mortar during the pull-off test is far more common while the mortars are applied on dried substrate. Each of the admixtures studied proved to be useful in improving the performance of the mortar in at least one of the studied conditions.
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The usability of secondary raw materials in the design of liquefied suspensions based on soil
Hrubý, Jakub ; Kulísek, Karel (referee) ; Černý, Vít (advisor)
The bachelor's thesis deals with the usability of secondary raw materials in the design of liquefied suspensions based on soils in the form of self-compacting grouts. The soil treated in this way can be used as a substitute for backfill material for excavations of engineering networks. The theoretical part deals with the classification and description of soils. Furthermore, the types of soil stabilization using lime, cement, including their liquefaction, are mentioned. A wide range of potentially suitable secondary raw materials and liquefaction mechanization is presented. In the practical part, the basic soil F6-Cl is selected on the basis of a set of available soils. The basic reference mixture consists of soil, lime, cement and liquefier. A proposal for the concept of experimental verification is presented. Part of the concept is the automated calculation of input raw materials. The effect of the action of the superabsorbent polymer and the accelerating additive is verified. Based on optimization selections, functional secondary raw materials are selected. The basic recipe with the optimal amount of accelerating ingredient achieves the best results. Recycled concrete and brick generally improve the resulting parameters. Bed ash achieves the highest strength with the lowest shrinkage.
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Study of shrinkage reducing admixture efficiency in alkali activated systems
Fojtík, Ondřej ; Koplík, Jan (referee) ; Bílek, Vlastimil (advisor)
Significant drying shrinkage is one of the major issues for the wider application of materials based on alkali-activated slag (AAS). Some shrinkage reducing admixtures (SRA) were developed for the ordinary portland cement systems. A couple of previous studies focused on the efficiency of these SRA in alkali-activated materials. The studies were mainly concentrated on the SRA based on polypropylene glycol. This thesis deals with efficiency of the SRA based on 2 methyl-2,4-pentanediol in AAS pastes and mortars. Influence of the SRA and activator (waterglass) dose on the drying shrinkage and other properties of AAS (flexural and compressive strength, autogenous shrinkage, workability, setting time and microstructure) were investigated. It was found, that at the activator dose when Na2O/slag mass ratio equals 4 or 6 %, SRA causes retardation of hydration, which leads to shrinkage reduction, however strength is reduced significantly, weight lost during the drying is increased and the coarsening of the pore structure occurs. At the activator dose when Na2O/slag mass ratio reaches 8, 10 or 12 %, in the presence of SRA the drying shrinkage is reduced, weight lost during the drying is similar to the reference, strength is increased and microstructure is unchanged against reference. It has been proved that SRA works properly in AAS only at higher activator doses.
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The possibility of using admixtures for waterroof concrete
Roháček, Lukáš ; Voves, Jiří (referee) ; Hubáček, Adam (advisor)
Bachelor thesis is mainly focused on additions, that have impact on water impermeability and other properities of fresh and hardened concrete. This issue is also described in short section, which is took from foreign reaserch. Thesis further discusses about the standards and regulations that determine, what properties should have waterproof constructions. Experimental part is showing influence of fly ash, slag and silica fume on conzistency, hydratation heat development, strenght, water impermeability, frost resistance and volume changes of the concrete.
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