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Research of effective use and activation of activ concrete additions
Mikhailova, Olesia ; Ťažký, Tomáš (referee) ; Hela, Rudolf (advisor)
The theoretical part describes the admixtures that are used in cement replacement. Here also summarizes the findings on the influence of granulomentry, grain shape and fineness of admixtures on the density of the cement matrix. The practical part is experimentally verified the influence of fineness admixtures and grain size on the mechanical properties of concrete. Also, the rheological properties of cement are compared with admixtures depending on the type and dosage and time.
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Production and characterization of biochar derived from different kind of bran
Černíková, Eliška ; Kalina, Michal (referee) ; Pořízka, Jaromír (advisor)
The bachelor thesis was focused on production and characterization of biochar prepared from different sorts of bran. According to the philosophy of circular economy bran, the biproduct of flour production, was chosen for the production of biochar. This lignocellulosic material was walked through pyrolysis to broaden potential application. Biochar was prepared by slow pyrolysis and considering its properties multiple applications are possible. Biochar’s usage is limited by European Biochar Certificate. The theoretical part contains general description of biochar properties, requests of European Biochar Certificate and possible analytical methods. In the practical part process of biochar preparation and biochar characterization per chosen methods are described. Analysed properties were: specific surface, pH, particle size distribution, electrical conductivity, composition of elements and content of polycyclic aromatic hydrocarbons. Based on measured data possible applications were recommended. Only biochar from rye bran fulfilled the strict criteria of European Biochar Certificate. However all of the prepared materials can be used in agriculture, except from rice bran biochar which according to EBC can only be used in material industry.
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Development of high quality autoclaved aerated concrete using alternative resources
Kostura, Patrik ; Janovský, Radek (referee) ; Drochytka, Rostislav (advisor)
With the growing trend of construction, the demand for building materials is growing steadily. Porous concrete is widely used in the building industry, that makes efforts to discount production and simultaneously save the environment. The aim of this thesis is to develop high-quality porous concrete by using alternative raw materials as a substitute for silicate sand. As a possible substitute were chosen: Silica masonry, foundry sand and fireclay boulders. The influence of two key parameters - the specific surface (130, 240 and 350 m2·kg-1) and the amount of silica sand substitution (10, 30 and 50 %) were monitored. Two autoclaving modes (7 and 12 hours of isothermal durations at 190 ° C) were tested. Based on the physico-mechanical and mineralogical characteristics of the porous concrete composites was chosen the ideal surface area of 240 m2·kg-1 and time of isothermal endurance was determined at 7 hours (temperature 190 ° C, pressure 1,4 MPa). From the optimal intentions were created samples with a macroporous structure, using an aluminum powder. Physical-mechanical properties and microstructural analysis (XRD, SEM) were subsequently determined on the samples. Ideal recipes were proposed with 50% sand substitution of fireclay boulders and 10% substitution of foundry sand. This was due to a 10% higher compressive strenght and an increase of the coefficient of constructiveness, compared to the reference sample.
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The Influence of Fines on Pore System of Concrete
Elfmarková, Veronika ; Smolka, Hynek (referee) ; Hela, Rudolf (advisor)
Literature does not provide a satisfactory answer to maximum and minimum particle size or the particle size of the mortar phase especially for optimal porosity of concrete. To overcome the shortcomings of the design methods were thought to design a new method for design of concrete mix. This idea is based on a complex analysis of powder materials (determination of granular properties, shape factor of fillers, porosity, packing of powder materials, surface area, etc.) and subsequently to assess the influence to pore system of concrete and physical and mechanical properties in hardened state of concrete. In this work are presented and analyzed two types of fillers – fly ash and limestone dust.
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Production and characterization of biochar derived from different kind of bran
Černíková, Eliška ; Kalina, Michal (referee) ; Pořízka, Jaromír (advisor)
The bachelor thesis was focused on production and characterization of biochar prepared from different sorts of bran. According to the philosophy of circular economy bran, the biproduct of flour production, was chosen for the production of biochar. This lignocellulosic material was walked through pyrolysis to broaden potential application. Biochar was prepared by slow pyrolysis and considering its properties multiple applications are possible. Biochar’s usage is limited by European Biochar Certificate. The theoretical part contains general description of biochar properties, requests of European Biochar Certificate and possible analytical methods. In the practical part process of biochar preparation and biochar characterization per chosen methods are described. Analysed properties were: specific surface, pH, particle size distribution, electrical conductivity, composition of elements and content of polycyclic aromatic hydrocarbons. Based on measured data possible applications were recommended. Only biochar from rye bran fulfilled the strict criteria of European Biochar Certificate. However all of the prepared materials can be used in agriculture, except from rice bran biochar which according to EBC can only be used in material industry.
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Development of high quality autoclaved aerated concrete using alternative resources
Kostura, Patrik ; Janovský, Radek (referee) ; Drochytka, Rostislav (advisor)
With the growing trend of construction, the demand for building materials is growing steadily. Porous concrete is widely used in the building industry, that makes efforts to discount production and simultaneously save the environment. The aim of this thesis is to develop high-quality porous concrete by using alternative raw materials as a substitute for silicate sand. As a possible substitute were chosen: Silica masonry, foundry sand and fireclay boulders. The influence of two key parameters - the specific surface (130, 240 and 350 m2·kg-1) and the amount of silica sand substitution (10, 30 and 50 %) were monitored. Two autoclaving modes (7 and 12 hours of isothermal durations at 190 ° C) were tested. Based on the physico-mechanical and mineralogical characteristics of the porous concrete composites was chosen the ideal surface area of 240 m2·kg-1 and time of isothermal endurance was determined at 7 hours (temperature 190 ° C, pressure 1,4 MPa). From the optimal intentions were created samples with a macroporous structure, using an aluminum powder. Physical-mechanical properties and microstructural analysis (XRD, SEM) were subsequently determined on the samples. Ideal recipes were proposed with 50% sand substitution of fireclay boulders and 10% substitution of foundry sand. This was due to a 10% higher compressive strenght and an increase of the coefficient of constructiveness, compared to the reference sample.
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