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Influence of ionts on the efficiency of shrinkage reducing admixtures in alkali activated systems
Vašíčková, Kateřina ; Bílek, Vlastimil (referee) ; Kalina, Lukáš (advisor)
Alkali activated materials, especially when activated with waterglass, are subjected to substantial drying shrinkage that hinders their broader industrial application. The effect of shrinkage reducing admixtures (SRA), based on poly(propylene glycol), on drying shrinkage of alkali activated blast furnace slag (BFS) mortars was studied. The aim of this thesis is to determine the efficiency of SRA as well as the influence of different type of alkali activator with varying silicate modulus on drying shrinkage characteristics. It was observed that the high amount of alkalis positively influenced the effect of SRA. The higher the amount of alkalis, the lower the drying shrinkage was. It also caused more water to be incorporated in the alkali activated structure and prevent it from evaporation. Thus, the weight change of such mortars was the lowest. Reduced effect of SRA on mechanical strength properties was observed in mortars with low amount of alkalis which was connected with delayed hydration resulting in insufficient amount of created C-S-H gel. The presented thesis further discussed and underlines the role of different kinds of alkali ions as well as their amount on the properties of alkali activated BFS systems.
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Effect of the composition of alkaline activator on the properties of hybrid cements
Šimko, Lukáš ; Vyšvařil, Martin (referee) ; Rovnaník, Pavel (advisor)
Building industry, especially production of Portland cement is the most ecologically and energetically demanding sector. Therefore, there is an effort of using waste products of energy industry as a (partial) substitution of conventional building materials. This bachelor thesis deals with the possibility of using the power station fly ash as a major part of mixtures with Portland cement, and therefore as a hybrid cement. In the experimental part, the influence of silicate module on the characteristics of mortars, whose binder is composed of 20% of Portland cement and 80% of fly ash from Dětmarovice power station, is examined. It further deals with influence of composition of alkaline activator on its characteristics. Its properties are examined in terms of porosity, strength and microstructure. Size and distribution of pores are examined by means of mercury intrusion porosimetry and evaluation of microstructure is based on scanning electron microscopy.
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The development of composites based on inorganic binders designed for the extreme applications
Janoušek, Petr ; Šácha, Libor (referee) ; Dufka, Amos (advisor)
The topic of this master's thesis is the development of composite materials based on inorganic binders for use in extreme conditions. It means especially geopolymeric or alkali activated materials (AAM) based composites. The theoretical part of this thesis summarizes knowledges about the development and use of alkali-activated materials, their structure and mechanisms of their formation. It also deals with the applicable raw materials for AAM and their exciters, which are in particular water glass and sodium hydroxide. There also have been a summary of the effects of high temperatures and chemicals on the mechanical properties of AAM and the requirements of standard EN 1504-3 for repairing materials. The task of the practical part was to develop a repair mortar for concrete structures based on AAM so that its production was as simple as possible, ie one-component materials. Gradually six recipes have been develeoped. Test specimens made from these recipes have been putted to selected tests according to the requirements of ČSN EN 1504-3.
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Durability of alkali-activated systems
Šafář, Martin ; Šoukal, František (referee) ; Kalina, Lukáš (advisor)
Alkali activated binders have the potential to become an alternative construction material to ordinary portland cement binders. This thesis concentrates on durability testing of alkali activated blast furnace slag and fly ash based concrete. The chosen aspects of durability included sulfate resistance, acid resistance, carbonation, freeze-thaw resistance, frost-salt resistance and porosity. Microstructural changes and formation of new crystalline phases were observed using XRD and SEM-EDX analysis. Potential application of the tested material from the durability point of view was evaluated by comparison with a reference ordinary portland cement based concrete.
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Possibilities of the utilization of the waste sand from the water glass production in building industry
Bílek, Vlastimil ; Kalina, Lukáš (referee) ; Opravil, Tomáš (advisor)
Nowadays, the waste sands from the water glass production have no utilization and due to high alkali content are considered as a dangerous waste. So the aim of this thesis is to find and study some possibilities of their utilization in the building industry. First of all, some necessary analysis of these sands were performed and then some advantages and disadvantages of their application for production of materials based on portland cement and alkali activated materials were studied. Characteristics of fresh and hardened pastes, mortars and concretes containing these waste sands were determined. The most tested properties were their workability and their compressive and flexural strength. Close attention for the risks of alkali-silica reaction and for options of its suppressing by the mineral admixtures was paid.
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Influence of inorganic admixtures on shrinkage reduction of alkali activated materials
Šístková, Pavlína ; Koplík, Jan (referee) ; Kalina, Lukáš (advisor)
This bachelor thesis is focused on the influence of inorganic admixtures on shrinkage reduction of alkali activated materials. In the theoretical part the issue of alkali activated materials is explained in detail focusing on the reduction of their shrinkage. Alkali activated system is constituted by alkali activated blast furnace slag. Firstly, the effect of inorganic dashes is monitored such as low calcium fly ash and finely ground limestone. Furthermore, the influence of inorganic additives for reducing shrinkage has been studied, namely magnesium oxide and calcium oxide. The aim of this work is to determinate the mechanical properties and shrinkage of individual alkali activated mixture and then discuss whether there was a reduction of shrinkage and what the effect of added dashes and inorganic admixtures was.
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