|
|
Study of synthetic sandstones preparation possibilities
Solik, Jaroslav ; Kalina, Lukáš (referee) ; Opravil, Tomáš (advisor)
This thesis explores the possibility of developing synthetic sandstones based on alkaline-activated (geopolymer) binders. The goal is to design an appropriate connective system of optimal concentration, so that the prepared material (artificial stone) showed similar characteristics as natural. The experimental section summarizes the experiments that explore several different alkali connective systems. The aim is to compare the properties of binders prepared from methakaolin (Mefisto K-05 and L-05) alkali-activated by sodium or potassium water glass. For comparison with these connective systems were also prepared samples of commercially supplied geopolymer binder called Baucis
|
|
|
Geopolymers Incorporating Wastes and Composites Processing
Taveri, Gianmarco ; Perná,, Ivana (referee) ; Pouchlý, Václav (referee) ; Dlouhý, Ivo (advisor)
Buildings construction and realization of public infrastructures have always been a primary need in the human society, developing low cost and user-friendly materials which also encounter safety and durability requirements. Portland cement is the most used material in construction industry from the industrial revolution up to date, but the raising concerns related to the climate change are pushing the governments worldwide to replace it with more eco-friendly and greener materials. Geopolymers are considered to be best alternatives to Portland cement in construction industry, but issues related to cost and mechanical properties are still hindering the commercialization of this material. Geopolymer incorporating wastes is one of the solutions. Fly ash, a thermal power plant by-product, and borosilicate glass, a recycled glass from pharmaceutical vials, are suitable candidates in geopolymers activation. NMR and FTIR spectroscopies demonstrated that borates from borosilicate glass are active compounds in geopolymerization, substituting the alumina is its role, composing a B-Al-Si network never observed before. Various fly ash and borosilicate glass weight contents were studied in terms of mechanical properties (compression test, 3-point bending test). It was found that fly ash 55 wt.% and borosilicate 45 wt.% composition activated in 13 M NaOH solution holds the best compressive and flexural strength (45 and 4 MPa respectively), 25% stronger than similar counterparts found in literature. Cellulose fibres in different weight contents were dispersed into the geopolymeric paste to produce geopolymer composites, with the aim to render the material more suitable for structural applications. 3-point bending test showed an improvement of the flexural strength of about 165% (12 MPa), while the chevron notch method displayed a fracture toughness of 0.7 MPam1/2, in line with the results of geopolymer composites found in literature. In this thesis work, fly ash was also successfully densified in 3 M NaOH solution and distilled water through a new method based on hydraulic pressure, called hydro-pressure sintering. This innovative technology involves a drastic reduction of NaOH utilization in geopolymerization, rendering the material more eco-friendly. XRD spectroscopy conducted on produced samples revealed a higher formation of crystals, most likely induced by the application of hydraulic pressure (450 MPa).
|
|
| |
|
|
Modification of the properties of alkali activated materials by polymer admixtures
Mikhailova, Olesia ; Bílek, Vlastimil (referee) ; Vejmelková,, Eva (referee) ; Žižková, Nikol (referee) ; Rovnaník, Pavel (advisor)
V současné době se v betonářském průmyslu ve velké míře používá portlandský cement (PC), jehož výroba má značný dopad na životní prostředí a zároveň se jedná o neudržitelný proces. Snahy o ekologičtější stavebnictví zahrnují využití několika aluminosilikátů, které mohou být buď odpadními produkty získanými z jiných průmyslových výrob, jako je granulovaná vysokopecní struska, popílek a křemičitá dýmka, nebo materiály pocházející z energeticky méně náročných průmyslových procesů, jako je metakaolin. Použití těchto materiálů při výrobě stavebních materiálů rovněž přispívá ke snížení výrobních nákladů. Aktivace aluminosilikátových materiálů alkalickými aktivátory vede k získání vysoce pevných materiálů, které lze považovat za alternativu běžného PC. Navzdory mnoha výhodám alkalicky aktivovaných aluminosilikátů (AAA) existuje zásadní nevýhoda, která se týká výrazného autogenního smršťování a smršťování při vysoušení, k němuž může docházet během tuhnutí materiálu. Tento jev vede k mikrotrhlinám a zhoršení mechanických lomových vlastností. Polymerní příměsi mohou modifikovat vlastnosti čerstvého a vytvrzeného materiálu AAA a překonat výše uvedené problémy. Tato disertační práce se zabývá vlivem polymerních přísad v různých hmotnostních množstvích aluminosilikátového pojiva na snižování smrštění a křehkosti a na zvýšení lomové houževnatosti. Jako polymerní příměsi byly vybrány polyetylen glykol (PEG), polypropylen glykol (PPG) a různé typy komerčních polymerů z řady dispergovatelných polymerních prášků Vinnapas®. Jejich vliv na vlastnosti získaných materiálů byl porovnáván s vlivem práškového přípravku proti smrštění Peramin SRA 40. Vzorky byly testovány na pevnost v ohybu a tlaku a jejich mikrostruktura byla zkoumána pomocí rtuťové porozimetrie a skenovací elektronové mikroskopie. Jedna z kapitol práce se zabývá studiem různých charakterizačních technik vzniku hlavních reakčních produktů v alkalicky aktivované strusce, jako jsou RTG difrakční analýza, Fourierovou tran
|
|
|
Geopolymers Incorporating Wastes and Composites Processing
Taveri, Gianmarco ; Perná,, Ivana (referee) ; Pouchlý, Václav (referee) ; Dlouhý, Ivo (advisor)
Buildings construction and realization of public infrastructures have always been a primary need in the human society, developing low cost and user-friendly materials which also encounter safety and durability requirements. Portland cement is the most used material in construction industry from the industrial revolution up to date, but the raising concerns related to the climate change are pushing the governments worldwide to replace it with more eco-friendly and greener materials. Geopolymers are considered to be best alternatives to Portland cement in construction industry, but issues related to cost and mechanical properties are still hindering the commercialization of this material. Geopolymer incorporating wastes is one of the solutions. Fly ash, a thermal power plant by-product, and borosilicate glass, a recycled glass from pharmaceutical vials, are suitable candidates in geopolymers activation. NMR and FTIR spectroscopies demonstrated that borates from borosilicate glass are active compounds in geopolymerization, substituting the alumina is its role, composing a B-Al-Si network never observed before. Various fly ash and borosilicate glass weight contents were studied in terms of mechanical properties (compression test, 3-point bending test). It was found that fly ash 55 wt.% and borosilicate 45 wt.% composition activated in 13 M NaOH solution holds the best compressive and flexural strength (45 and 4 MPa respectively), 25% stronger than similar counterparts found in literature. Cellulose fibres in different weight contents were dispersed into the geopolymeric paste to produce geopolymer composites, with the aim to render the material more suitable for structural applications. 3-point bending test showed an improvement of the flexural strength of about 165% (12 MPa), while the chevron notch method displayed a fracture toughness of 0.7 MPam1/2, in line with the results of geopolymer composites found in literature. In this thesis work, fly ash was also successfully densified in 3 M NaOH solution and distilled water through a new method based on hydraulic pressure, called hydro-pressure sintering. This innovative technology involves a drastic reduction of NaOH utilization in geopolymerization, rendering the material more eco-friendly. XRD spectroscopy conducted on produced samples revealed a higher formation of crystals, most likely induced by the application of hydraulic pressure (450 MPa).
|
|
|
Research of interface between quartz and non quartz mould materials grains and geopolymer binder
Skřivánková, Vendula ; Burian,, Alois (referee) ; Cupák, Petr (advisor)
Presented thesis deals with monitoring of the properties of the interface between opening materials and geopolymer binder using three quartz and four non quartz opening materials. There is observed mainly the type of destruction of connective bridges. The theoretical part of the thesis briefly summarizes commonly used methods in foundries and monitors experience with implementation of geopolymers in different foundries. The practical part monitors shape of the grains of the chosen opening materials. There are writed down the results from the measurement of the bending strength and workability and there is observed the type of destruction of connective bridges.
|
|
|
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.
|
|
|
Modification of concrete elements for cooling towers
Mohelská, Lucie ; Šoukal, František (referee) ; Opravil, Tomáš (advisor)
This master´s thesis deals with the suppression of the growing of algae in cooling towers. Subject of the work is suggestion and testing surface modification of the existing mature concrete in order to suppress the growth of algae. In the frame surface modification, several commercially available and newly developed systems were tested. Testing systems are based on the basis of portland cement, geopolymers or formation of insoluble complex compounds containing metal elements (Zn, Cu). Experimental methods were applied in the real environment of cooling towers of Dukovany Nuclear power plant.
|
|
|
The possibilities of using of foundry filter ash
Solik, Jaroslav ; Šoukal, František (referee) ; Opravil, Tomáš (advisor)
This thesis explores the posibility of using of foundry filter ash for production of inorganic composite materials, that could be used primary in the construction industry. The thesis is divided into theoretical and experimental section, where theoretical section contain literature review of used materials and the experimental section summarizes the results of laboratory tests performed on tested mixture based on portland and alumina cement with various content of foundry filter ash. For comparison was also used another foundry waste - foundry sand. Prepared test bodies with dimension of 40 x 40x 160 mm was subjected to mechanical strength tests and the influence of amount of foundry waste on the strenght of the prepared mixtures was monitored. Next the thesis deals with possibilities of alkaline activation of foundry waste, where sodium water glass, sodium hydroxide and commercially supplied baucis L 160 component B were used as alkaline activator. These test mixtures were also subjected to mechanical strenght tests and the influence of amount of foundry waste on the strenght was observed too. The analysis of input materials were performed by XRF, TG – DTA – EGA and XRD powder diffraction methods. All strength tests were tested by testing equipment desttest 4310.
|
|
| |
guest ::
