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Hybrid systems based on alkali activated materials and Portland cement
Bradová, Lada ; Koplík, Jan (referee) ; Kalina, Lukáš (advisor)
The most promising route to improve the sustainability of cement is to produce the blended Portland cements with supplementary cementitious materials. Blast furnace slag (BFS) is one of the significant pozzolan source used worldwide in blended cements contributing to lowering of the environmental impact of cement industry. On the other hand, the replacement of the Portland clinker is connected with the undesirable effects such as reduction of early strength development. In order to overcome this disadvantage, the study deals with the development of hybrid cements in which the utilization of solid waste alkaline activator quickly awakens the pozzolanic properties of BFS. The new types of blended alkali activated cements were designed to meet the European standard EN 197 1 and classified to the Blastfurnace CEM III/C cements in accordance with the mechanical, physical, chemical and durability requirements. The effect of alkali activation caused an increase in early (2 days) compressive strength development in comparison with reference sample. The setting time was delayed two times which is also interesting from the point of view of concrete production. Moreover, this non traditional hybrid alkali activated Portland cement provides considerable ecologically and economically potential.
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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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Validation of an innovative approach to the design of alkali-activated materials
Kejík, Marek ; Kucharczyková, Barbara (referee) ; Bílek, Vlastimil (advisor)
This thesis presents an approach to express the composition of alkali-activated materials based on three main characteristics. These are the type of activator, the molarity of the activator, and the volume fraction of the precursor or aggregate. The aim of this work is to provide a practical verification of this approach, in particular with respect to the amount of precursor, aggregates, and activator at a constant molarity of the three basic activator types (Na2CO3, NaOH, sodium water glass). The effects of these factors on their basic properties, namely workability, shrinkage, and mechanical properties, were studied for the prepared samples of pastes and mortars based on alkali-activated slag. These results were further supported by mercury intrusion porosimetry and electron microscopy. The results obtained confirmed the assumed key influence of the volumetric representation of the precursor, aggregates, and activator on the absolute values of the studied properties as well as on their relative changes. These were very different for the different activators, which is mainly due to the different abilities of the hydration products formed to fill the space between the slag and aggregate grains. The result of this work is a summary of the knowledge about the properties of alkali-activated materials over a given range of compositions, anchored by a universal approach for the design of the composition of these materials, which can be used in further research in this field.
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Utilization of lignosulfonate plasticizer in alkali-activated materials
Zetocha, Martin ; Hrubý, Petr (referee) ; Kalina, Lukáš (advisor)
Tato bakalářská práce se zabývá využitím plastifikátorů na bázi lignosulfonátu v alkalicky aktivovaných materiálech. Sledován byl vliv na směs pasty aktivované vysokopecní strusky za použití hydroxidu sodného, vodního skla o různých modulech a uhličitanu sodného. Pozorován byl vliv plastifikátoru na bázi lignosulfonátu při zamíchávání do různých směsí, na zpracovatelnost, mechanické vlastnosti a reologii směsi. Důležitým faktorem byly použité aktivátory ve směsích. Nejlépe reagující směs na lignosulfonát se ukázala být za použití NaOH jako aktivátoru. Při pokusech pochopit reologické vlastnosti sledovaných směsí, jako klíčového faktoru chování těchto směsí bylo měření zeta potenciálu. Hodnoty zeta potenciálu nám daly bližší náhled na povrchový náboj častic vysokopecní strusky. Ten se prokázal jako klíčový faktor při posuzovaní účinnosti plastifikátoru. Tato zjištění budou vzata v úvahu a dále diskutovány v této práci.
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Effect of curing conditions on shrinkage of alkali activated systems
Pragerová, Barbora ; Kotrla, Jan (referee) ; Kalina, Lukáš (advisor)
This bachelor thesis deals with the determination of optimal curing conditions of alkali-activated systems in order to reduce shrinkage. Hardened alkali-activated blast-furnace slag pastes activated by sodium silicate were tested in the empirical part. Six varieties of curing conditions were compared. Immediately after demolding process, three sets of samples were stored in air, water and plastic film. Another three sets were first placed in water for 14 days, then removed and two of them impregnate with lithium silicate and acrylate-based coatings. The formation and the number of cracks were monitored by an optical method. The percentage of cracks was evaluated by the ImageJ program. The highest number of cracks was formed after 7 days of curing, given the samples placed in the open air. Some them were filled later. Samples placed in the open air after being submerged in water for 14 days showed a rapid increase of cracks as well, but the percentage of cracks was reduced to 50 %. Treating agents reduced the development of cracks but have not stopped their formation. After 36 days of curing, the results of these types of curing conditions were comparable. Only the samples wrapped in plastic foil showed a minimum number of cracks and no cracks were observed if the samples were submerged in water. The lowest levels of shrinkage were reached with the samples placed in water, and with the ones wrapped in plastic foil. Samples stored in water for the first 14 days showed the identical tendency of high-level shrinkage, as did the ones placed in the open air.
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Study of alkali-silica reaction in hybrid systems
Bradová, Lada ; Bílek, Vlastimil (referee) ; Kalina, Lukáš (advisor)
This study evaluates question of alkali–silica reaction (ASR) in hybrid system, which was designed in the bachelor's thesis, to meet the requirements of EN 197-1 and classified to the Blastfurnace CEM III/C cements. The durability of this system is a great unknown. For this reason, the same methods (ASTM C1260, ASTM C289 and ASTM C856) were used to observer the ASR effects as the ones used to observer the Portland cement based concrete. Supplementary methods include determination of compressive strengths according to EN 196-2 and scanning electron microscopy to observe the microstructure. Hybrid system results were compared to two different types of cements, CEM I and CEM III/B. From the results of the ASR evaluation assays, it was found that the hybrid system (CEM III/C-HB) and CEM III/B showed the lowest tendency to ASR. The results of the supplementary methods showed that CEM III/C-HB compressive strength increases after 14 days within NaOH by 43 % in comparison to 28 days strength. Based on those results, it is sure that the CEM III/C-HB shows little susceptibility to ASR.
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Low-Cost Filtration Barriers for Ultrafine Particles Separation
Kejík, Pavel ; Fekete, Roman (referee) ; Lapčík, Ĺubomír (referee) ; Svěrák, Tomáš (advisor)
V mnoha oborech jsou stále využívána anorganická filtrační media založená na materiálech, jejichž výroba využívá primární suroviny. Jejich výroba je tedy energeticky náročná a v důsledku nákladná a neohleduplná k životnímu prostředí. Cílem této práce je ověřit možnost využití alkalicky aktivovaných materiálů na bázi sekundárních surovin, především vysokopecních strusek (BFS) a popílků z uhelných elektráren (FA), pro výrobu porézních médií schopných v budoucnosti nahradit keramické a jiné anorganické filtry. Výzkum je rozvinut skrze experimentální design založený na výpočetním schématu samostatně vyvinutém s pomocí programu MATLAB. Toto schéma počítá vhodná složení směsí na základě poměrů obsahu nejdůležitějších oxidů ve vstupních surovinách. Tak je zajištěno zohlednění proměnlivého složení vstupních surovin a práce je tím hodnotnější, že její výsledky jsou skrze početní nástroj zohledňující základní oxidové složení surovin zobecnitelné. Zároveň byly však pro srovnání a lepší názornost závislostí vlastností na složení navrhnuty a připraveny i série vzorků založené vždy pouze na jedné ze surovin. Z výsledků vyplývá, že pevnost vzorků z těchto směsí (vytvrzených 24 hodin při 70 °C) ve čtyřbodové ohybové zkoušce dle ČSN EN 12390 5 může přesáhnout 7,6 MPa. Dosažením co možná nejvyšší porozity však zákonitě negativně ovlivňuje pevnost materiálu a výsledný materiál tedy dosahuje pevnosti těsně nad hranicí 6,3 MPa. Výsledky obecně dokazují, že nejvíce je pevnost materiálů ovlivněna poměrem SiO2/Al2O3 a množstvím alkalického aktivátoru. Z výsledků vyplývá, že alkalicky aktivované materiály (AAM) na bázi strusky dosahují i více než dvojnásobné pevnosti analogických materiálů na bázi elektrárenského popílku. Velikost pórů materiálů připravených z tříděných surovin s velikostí zrna od desítek po lehce přes sto mikronů se ve většině případů pohybuje v rozmezí desetin ž jednotek mikronů, v případě výsledného materiálu je to pak přibližně 0,2 mikronu. Celková porozita lisovaných těles se pohybuje těsně pod 40 %, což je v tomto případě téměř dvojnásobek ve srovnání s totožnými materiály na bázi netříděných surovin. Výsledky rovněž ukazují, že materiály na bázi strusky vykazují nižší porozitu než ty na bázi popílku, což je patrně způsobeno rozdílnou morfologií částic obou materiálů – částice strusky jsou nepravidelně hranaté a částice popílku kulaté. V průběhu experimentální činnosti byla pozorována tvorba výkvětů u materiálů na bázi elektrárenských popílků. Pomocí Energo-disperzní spektroskopické analýzy (EDS) byly výkvěty identifikovány jako hydroxid sodný procházející karbonatací za účasti vzdušného CO2. Test permeability vyžadoval, kvůli velmi jemné povaze porézní struktury, přípravu asymetrických filtračních přepážek. Tyto přepážky dosáhli propustnosti 138 L/h.m2.bar pro vodu a 1320 L/h.m2.bar pro vzduch.
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Effect of selected activators on the properties of alkali-activated composites reinforced with basalt fibers
Švardala, Daniel ; Hrubý, Petr (referee) ; Kalina, Lukáš (advisor)
This paper deals with the alkali activated materials (AAM) applicable as a construction material, thanks to low cost, environmental friendliness and good mechanical properties. The goal of this thesis is to search for suitable alkaline activator with respect to the final properties of alkali activated composite reinforced with basalt fibers. This thesis is focused on the determination the effect of basalt fibers addition on the mechanical properties. The influence of alkaline activator to basalt reinforcement was determined by simply strength tests, like the compressive and flexural strength measurements. The matrix fiber interaction, as one of the main parameters indicating the quality of the material reinforcement, was measured by electron scanning microscope equipped with an X ray energy dispersing analyzer (SEM EDS). It was found out that the most significant effect on the improvement of the mechanical properties of alkali activated material was in the case of the samples activated by sodium and lithium waterglass. The mechanical strength of these reinforced materials was considerably higher compared to non reinforced samples. AAM activated by potassium waterglass with and without the basalt reinforcement indicates the same or very similar mechanical strength. The comparison of composites with different alkaline activator leads to the conclusion that the mechanical properties depend on the type of used waterglass. AAM activated by sodium waterglass achieve the highest strengths compared to potassium and lithium waterglass activated materials and therefore seems to be the most appropriate for basalt fiber composites preparation.
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Blast furnace slag as a component of hydraulic binders
Velebný, Josef ; Faltus, Miloš (advisor) ; Kuchařová, Aneta (referee)
The aim of this work is to evaluate blast furnace slag as an additive in hydraulic binders. These additives favorably affect the mechanical, chemical and phase properties of cements and binders on their basis. Basic structural and chemical analyzes of studied slags and reference cement and structural analyzes of hydrated binders were carried out on their basis. Furthermore, this thesis deals with testing and comparison of mechanical properties of mortar test bodies based on Reference Portland cement itself and with the addition of finely ground granulated and air cooled blast furnace slag and the development of these properties over time. Subsequently, these results are compared and made out about the usability of the studied materials for the production of hydraulic binders as compared to cements without added slag depending on time. Testing of mechanical properties according to the relevant standard ČSN EN 12390. Attention is paid mainly to the development of compressive strength and flexural tension. The XRD and XRF methods were used to study the phase and chemical composition of studied materials and hydrated binders based on these. Keywords: Slag, portland slime, hydraulic binder, Portland cement, blast furnace slag, phase composition, glass phase, latent hydraulicity, pozolanita, alkaline...
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