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1
Adediran, A. (Adeolu). "Alkali activation of fayalite slag." Master's thesis, University of Oulu, 2017. http://urn.fi/URN:NBN:fi:oulu-201709062801.
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In this thesis, alkali activation of fayalite slag was investigated. The slag utilized is a waste by product from nickel production, the activation of which resulted in the formation of a geopolymer binder of acceptable properties. The need for a reduction in overall waste output as well as the cementitious properties exhibited by this slag motivated this study.
The literature section of this research provides an insight on the previous work in the area of geopolymerization, the source materials used, the activators employed as well as the properties exhibited by various geopolymer products. The experimental section reports the particle size distribution and particle size optimization as well as geopolymer synthesis. The size reduction was carried out by milling for a required time while the particle size optimization and mix design was done with “Elkem Material Mixture Analyser (EMMA).
The milling reduced the particle size of fayalite slag to 10.08 µm after 3 hours which is sufficient fineness for most geopolymer precursors. Different mix compositions were activated with potassium silicate and sodium hydroxide at varying mass ratio with the one activated with 50:50 mass ratio of NaOH /K₂SiO₃ had the highest mechanical strength. The workability and setting time were good for the mixtures with liquid to solid ratio from 0.1–0.2. Compressive strength test were carried out on various mix compositions and the result shows the maximum compressive strength of 16.5 MPa was achieved at room temperature after 28 days. The water absorption was very low (5%). It was also noticed that the strength after water absorption was higher than the unconfined compressive strength due to subjection of slag geopolymer to elevated temperature before water absorption.
The alkali activation of fayalite slag has shown promising properties which could further be improved for better mechanical performance.
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Yliniemi, J. (Juho). "Alkali activation-granulation of fluidized bed combustion fly ashes." Doctoral thesis, Oulun yliopisto, 2017. http://urn.fi/urn:isbn:9789526215624.
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Abstract Biomass, such as wood, binds CO2 as it grows, and is thus considered an environmentally friendly alternative fuel to replace coal. In Finland, biomass is typically co-combusted with peat, and also municipal waste is becoming more common as a fuel for power plants. Wood, peat and waste-based fuels are typically burned in fluidized bed combustion (FBC) boilers. Ash is the inorganic, incombustible residue resulting from combustion. The annual production of biomass and peat ash in Finland is 600 000 tonnes, and this amount is likely to increase in the future, since the use of coal for energy production will be discontinued during the 2020s. Unfortunately, FBC ash is still largely unutilized at the moment and is mainly dumped in landfills. The general aim of this thesis was to generate information which could potentially improve the utilization of FBC ash by alkali activation. The specific objective was to produce geopolymer aggregates by means of a simultaneous alkali activation-granulation process. It was shown that geopolymer aggregates with physical properties comparable to commercial lightweight expanded clay aggregates (LECAs) can be produced from FBC fly ash containing heavy metals. Although the ashes were largely unreactive and no new crystalline phases were formed by alkali activation, a new amorphous phase was observed in the XRD patterns, possibly representing micron-sized calcium aluminate silicate hydrate-type gels. The heavy metal immobilization efficiency of alkali activation varied with the type of fly ash. Good stabilization was generally obtained for cationic metals such as Ba, Pb and Zn, but in common with the results obtained with alkali activation of coal fly ash, anionic metals became leachable after alkali activation. The efficiency of immobilization depended on the physical and chemical properties of the fly ash and was not related to the total content of the element. All the geopolymer aggregates met the criteria for a lightweight aggregate (LWA) as defined by EN standard 13055-1. Their strength depended on the reactivity and particle size distribution of the fly ash. Mortars and concretes prepared with such geopolymer aggregates had higher mechanical strength, higher dynamic modulus of elasticity and higher density than concrete produced with commercial LECA, while exhibiting similar rheology and workabilityTiivistelmä Biopolttoaineet, esimerkiksi puu, ovat ympäristöystävällinen vaihtoehto kivihiilelle, koska ne sitovat hiilidioksidia kasvaessaan. Suomessa biopolttoaineita poltetaan tyypillisesti turpeen kanssa, ja nykyään myös jätteen hyödyntäminen polttoaineena on yleistynyt. Puu, turve ja jätepolttoaineet poltetaan tyypillisesti leijupetipoltto-tekniikalla. Tuhka on polton epäorgaaninen, palamaton jäännös. Puun ja turpeen tuhkaa tuotetaan Suomessa 600 000 tonnia vuodessa ja määrän odotetaan kasvavan, sillä kivihiilen poltto lopetetaan 2020-luvulla. Leijupetipolton tuhkaa ei tällä hetkellä juurikaan hyödynnetä ja tuhka päätyykin pääasiassa kaatopaikoille. Tämän tutkielman päämääränä oli tuottaa tietoa, joka parantaisi leijupetipolton tuhkien hyödyntämistä alkali-aktivaatiolla. Erityisesti tavoitteena oli valmistaa geopolymeeriaggregaatteja yhtäaikaisella alkali-aktivaatiolla ja rakeistuksella. Tutkielmassa osoitettiin, että raskasmetalleja sisältävistä tuhkista valmistettujen geopolymeeriaggregaattien fysikaaliset ominaisuudet ovat vertailukelpoiset kaupallisten kevytsora-aggregaattien (LECA) kanssa. Vaikka tuhkien reaktiivisuus oli matala, ja uusia kidefaaseja ei muodostunut alkaliaktivaatiolla, uusi amorfinen faasi havaittiin XRD-mittauksissa. Uusi amorfinen faasi oli mahdollisesti mikrometrikokoluokan kalsium-aluminaatti-silikaatti-hydraatti-tyyppinen rakenne. Raskasmetallien stabiloinnin tehokkuus vaihteli tuhkien välillä. Kationiset metallit, kuten barium, lyijy ja sinkki, stabiloituivat pääasiassa hyvin, mutta anionisten metallin liukoisuus kasvoi alkali-aktivoinnin myötä. Stabiloinnin tehokkuus riippui tuhkien fysikaalisista ja kemiallisista ominaisuuksista, mutta raskasmetallin kokonaispitoisuudella ei ollu vaikutusta. Kaikki geopolymeeriaggregaatit olivat kevytsora-aggregaatteja standardin EN 13055-1 mukaisesti. Aggregaattien lujuus riippui tuhkan reaktiivisuudesta ja partikkelikokojakaumasta. Geopolymeeriaggregaateilla valmistettujen laastien ja betonien mekaaninen lujuus, Youngin moduuli ja tiheys olivat korkeampia kuin kaupallisella kevytsora-aggregaateilla valmistetut, vaikka niiden reologia ja työstettävyys olivat samanlaisia
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Illingworth, James M. "Chemical activation of biomass fibre with alkali metal salts." Thesis, University of Leeds, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.417756.
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Sajja, Mani Bhushan. "Eco-friendly paving blocks from alkali-activation of basalt powder." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
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The main aim of the research is to investigate the waste by-products as a sustainable construction material by means of Alkali-activation processes. Nowadays, cement is one of the most significant factors of climate change and global warming. It accounts for 5% to 8% of total emission, which may increase due to the increase in concrete production. In this process, sustainable and eco-products have been chosen.
Basalt and metakaolin were chosen as precursors. In this, basalt is the main component of our research. Basalt is an igneous rock formed by the rapid cooling of lava at the surface of a planet and it is the most common rock in the earth’s crust and metakaolin is the anhydrous calcined form of the clay mineral kaolinite also the particle size of metakaolin is smaller than cement particles.
In this experimentation, there are two activators sodium silicate and sodium hydroxide. These two activators added into precursors in certain proportions and mixed using a cement rotator. After that, this mixture is distributed into cube blocks and leave for a few minutes before packing with a plastic cover. Proceeding into a curing process, these cube blocks placed in the oven at certain temperatures between 60 to 80 degrees.
These types of precursors and activators are added in different ratios using this procedure to make a cube sample following by the curing process of 28 days. These were tested in compressive strength machine to obtain load resistance results. Basalt has better chemical resistance to the extended operating temperature range and environmentally friendly material. Metakaolin is eco-friendly by reducing the amount of 〖co〗_2 emission and the heat of hydration leading to shrinkage and crack control.
With the obtained synthetic mixtures, some special paving blocks were produced. Following the EN 1338 standard, these were tested in different to fully characterize the final product.
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Unsal, Saglik Asli. "Alkali-silica Rectivity And Activation Of Ground Perlite-containing Cementitious Mixtures." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12611249/index.pdf.
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Perlite is a volcanic mineral. The latest investigations on ground perlite showed that it is suitable for pozzolanic usage. Thus, it is of vital importance especially for countries rich in perlite such as Turkey. The aim of this study is to investigate the advantages and problems associated with using perlite in concrete and to identify accurate methods and amounts of use for producing durable cementitious mixtures. Within the scope of this study, the alkali-silica reactivity of perlite containing cementitious mixtures were compared using four different methods. Expansion mechanism of the mixtures were tried to be understood by measuring the alkalinity of bath waters. In order to cope with early strength decreases caused by perlite addition, activation of the mixtures by chemical and thermal methods were attempted. It was found that chloride containing chemicals are very effective at later ages and sodium containing chemicals are more effective at early ages. Sodiumhydroxide addition to the perlite containing mixtures was found to be detrimental to both the initial and late-age strengths of mortars.
It was concluded that perlite addition generally results in a decrease in alkali-silica expansions. However, the expansion of concrete samples should be investigated comprehensively. Thermal curing at high temperatures resulted in a rapid increase at 1-day strengths, however, for better ultimate strengths lower thermal treatments or no-thermal curing were found to be more effective. Compared to the traditional portland cement concretes, high-volume ground perlite concretes have environmental and economical advantages.
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Bondar, Dali. "Alkali activation of Iranian natural pozzolans for producing geopolymer cement and concrete." Thesis, University of Sheffield, 2009. http://etheses.whiterose.ac.uk/14553/.
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The challenge for the civil engineering community in the near future will be to realize the building of structures in harmony with the concept of sustainable development, through the use of high performance materials which have low environmental impact and can be produced at reasonable cost. Geopolymers are novel binder materials that could provide a route towards this objective. Although research on geopolymer has advanced, most of the previous research conducted on geopolymers has dealt with pastes and concentrated on the material's chemistry and microstructure. There is little information available concerning the engineering and durability properties of geopolymer concrete and none considering the use of natural pozzolans for production of geopolymer concrete. This investigation has studied the potential of using five natural pozzolans from Iran as geopolymer precursors. Most of the raw materials contain zeolites and clay minerals and have a high loss on ignition. Therefore, trials were made where samples were calcined at 700, 800 and 900°C. The solubility of both the raw and calcined materials in an alkaline solution was used as an indicator for pozzolanic activity. Improvements in pozzolanic properties due to heat treatment and elevated curing temperatures (20, 40, 60, and 80°C) were studied by using alkali solubility, XRD and compressive strength tests. It has been found that geopolymer binders can be synthesized by activating natural pozzolans and condensing them with sodium silicate in a highly alkaline environment. A new model is presented which allows the prediction of the alkali activated pozzolan strength from information on their crystallinity, chemical compositions and alkali solubility. Two types of Iranian natural pozzolans, namely Taftan which can be activated without calcination and Shahindej which was calcined were selected for further activation to study the effect of the alkaline medium on the strength of the alkali-activated natural pozzolan. The effect of the type, form, and concentration (molarities =2.5, 5.0, 7.5, 10.0 M) of the alkaline hydroxide, the modulus of sodium silicate (Si02INa20 ratio =2.1, 2.4, 3.1) and different curing conditions on the geopolymerisation of the above two natural pozzolans were studied. The optimum range and contributions for each factor is suggested based on their effect on compressive strength. An optimum paste formulation has been developed for concrete mixing together with the procedure of addition of the raw materials to the reaction mixture and suitable curing methods for producing the geopolymer concrete derived from them. The properties of this geopolymer concrete in both the fresh and hardened states have been investigated in terms of setting time, workability, air content, compressive strength, splitting tensile strength, static modulus of elasticity, ultrasonic pulse velocity, and drying shrinkage. Studies related to durability such as gas permeability, chloride ion penetration, and sulphate resistance have been undertaken and compared to these for typical OPC concretes. Some problems were encountered in applying the standard concrete durability tests. In this study attempts have been made to determine the relationships between the different properties of geopolymer concrete with its compressive strength and compared to results for ope concrete, to help to explain the differences between alkali-activated natural pozzolan concrete and ope concrete. In the countries which have large resources of natural pozzolan, geopolymer concrete based on alkali activation of these resources can help decrease the energy consumption and environmental impacts involved in using traditional cement pastes.
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Adesanya, E. D. (Elijah D. ). "A cementitious binder from high-alumina slag generated in the steelmaking process." Doctoral thesis, Oulun yliopisto, 2019. http://urn.fi/urn:isbn:9789526224527.
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Abstract About 4 Mt of ladle slag is generated in steelmaking processes in Europe per year, a large proportion of which (80%) is placed in landfills or stored. This pattern is expected to continue without further research for their valorisation due to increasing demand for quality steel products worldwide. Ladle slag (LS) produced in Finland possesses large amounts of calcium and aluminium and mineralogical phases which can exhibit cementitious capabilities and can be utilized in applications where expensive commercial cements are currently being used. The aim of this thesis is to investigate the properties of ladle slag in different activation pathways, including alkali activation and use as a hydraulic binder with gypsum. The results showed that ladle slag can be used alone as a precursor in alkali activation or as the sole binder or a co-binder with gypsum in hydraulic binding. Depending on the activation pathway, compressive strength between 35–92 MPa can be achieved after 28 days. The reaction properties of alkali activated ladle slag are characterized, and it is confirmed through X-ray diffraction (XRD) that the reaction product after alkali activation is mainly an x-ray amorphous (calcium aluminate silicate hydrate-like) phase. Characterization techniques (SEM, XRD, TGA and NMR) used to analyze the LS paste binder with just water showed the hydration products of ladle slag to be dicalcium aluminate octahydrate (C₂AH₈), tricalcium aluminate hexahydrate (C₃AH₆), gibbsite (AH₃) and stratlingite (C₂ASH₈) was also identified after a prolonged period of hydration. Furthermore, it was found that to minimize the conversion, the ideal water-to-binder ratio is 0.35. The conversion mechanism is reduced at this ratio and the strength is slightly affected. Another pathway that can be used to annul the conversion of calcium aluminate hydrates formed in LS paste is through the addition of gypsum to the LS paste system to produce an ettringite-rich binder (C₆A\(\bar{S}\)₃H₃₂). When ettringite is formed in place of calcium aluminate hydrates the strength increases, frost resistance is improved, and drying shrinkage is enhanced. Lastly, a potential application of ladle slag as a refractory material was also investigatedTiivistelmä Euroopassa syntyy vuosittain noin 4 Mt terästeollisuden sivutuotetta, JV-kuonaa, josta 80 % läjitetään tai kaatopaikoitetaan. Maailmanlaajuisesti syntyvän kuonan määrä tulee todennäköisesti kasvamaan laadukkaiden terästuotteiden ennustetun kysynnän kanssa. Tämän vuoksi kuonalle tulisi löytää hyötökäyttökohde, jota vältyttäisiin läjitykseltä. JV-kuona sisältääkin suuria määriä kalsiumia ja alumiinia sekä mineralogisia faaseja, joilla on sementtimäisiä ominaisuuksia. Näin kuonaa voitaisiin käyttää sovelluksissa, joissa tällä hetkellä käytetään kalliita kaupallisia sementtejä. Tämän väitöskirjan tarkoituksena oli tutkia JV-kuonan ominaisuuksia sementtimäisenä sideaineena alkali-aktivoinnissa sekä hydraulisena sideaineena yksinään että kipsin kanssa sekoitettuna. Väitöskirjan tulokset osoittivat, että JV-kuonaa voidaan käyttää prekursorina alkali-aktivoinnissa tai hydraulisena sideaineena pelkästään veden kanssa tai yhdessä kipsin ja veden kanssa. Saavutetut puristuslujuuset vaihtelivat 35 ja 92 MPa:n välillä, jotka vastaavat normaalin ja erityislujan betonin lujuuksia. JV-kuonan reaktiotuotteet alkali-aktivonnin jälkeen analysoitiin XRD- ja FTIR-analyyseillä. Tuloksista nähtiin, että alkali-aktivoinnin jälkeen reaktiotuote on sementin kaltainen kalsium-aluminatti-silikaati-hydraati (C-A-S-H) -tyyppinen faasi. XRD-, SEM-, TGA- ja NMR-analyysit osoittivat JV-kuonan hydrataatiotuotteiden olevan erilaisia kalsium-aluminaattihydraatteja (C₂AH₈, C₃AH₆, AH₃ ja C₂ASH₈). Tämän vuoksi työssä tutkittiin eri vesi–kuona-suhteita, ja havaittiin, että kun käytetään alhaista kuona-vesi –suhdetta (0,35), reaktiotuoteiden muutos vähenee ja lujuus paranee. Toinen tapa, jolla voidaan estää reaktiotuotteiden muuttuminen, on kipsin lisäys: lisäämällä kipsiä tuotetaan runsaasti ettringiittiä (C₆A\(\bar{S}\)₃H₃₂). Kun ettringiittiä muodostuu kalsium-aluminaattihydraattien sijaan, lujuus kasvaa, pakkaskestävyys paranee ja kuivumiskutistuma paranee. Väitöskirjan viimeisessä osiossa tutkittiin JV-kuonan mahdollista käyttöä tulenkestävänä materiaalina ja huomattiin, että sen tulenkestävyysominaisuudet vaihtelevat käytetyn aktivointityypin mukaan
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Cherki, El Idrissi Anass. "Géopolymérisation et activation alcaline des coulis d’injection : structuration, micromécanique et résistance aux sollicitations physico-chimiques." Thesis, Ecole centrale de Nantes, 2016. http://www.theses.fr/2016ECDN0015/document.
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La nécessité de construire de manière durable, rationnelle et écologique incite à l’innovation et la recherche d’alternatives, telles que la géopolymérisation et l’activation alcaline, qui suscitent un intérêt croissant. Dans ce sens, ces technologies permettent de valorise rdes matières premières à plus faible impact environnemental pour le développement d’une nouvelle famille de matériaux. Cependant, ces mécanismes réactionnels sont complexes et il est encore nécessaire de lever plusieurs verrous avant leur implémentation : la confusion entre les deux processus, l’absence d’approches de formulation rationnelles, la méconnaissance de certaines vulnérabilités, etc. La thèse s’intègre dans cette dynamique et a pour objectif une meilleure connaissance des géopolymères et des matériaux alcali-activés. Le cadre de travail est le développement de coulis d’injection. Un programme expérimental basé sur une sélection de compositions est établi afin de caractériser leurs principales propriétés. Les différences entre les deux processus de structuration sont relevées à travers une étude physico-chimique (DRX, RMN) et liées aux évolutions macroscopiques au jeune âge. Un travail d’optimisation de formulation est mené afin de répondre à des critères d’application et définir les paramètres influençant le comportement rhéologique et mécanique des coulis. Une méthodologie basée sur l’analyse micromécanique et l’homogénéisation multi-échelles a permis d’évaluer le module élastique des matériaux et peut servir de plateforme pour une analyse globale du comportement mécanique. Enfin, une étude de la durabilité est entamée en évaluant la sensibilité au séchage et à la lixiviation en milieu acideThe need for more durable, rational and ecological constructions encourages innovation and the search for alternatives, such as geopolymerization and alkali-activation, with a growing interest. These technologies allow the use of resources with a lower environmental impact in developing a new class of materials. However, both reaction mechanisms are complex and some issues need further investigation before a proper implementation: the confusion between these processes, the absence of a rational design approach, the lack of knowledge concerning some mechanisms of degradation, etc. The present thesis joins this dynamic and aims at a better understanding of geopolymers and alkali activated materials to design soil injection grouts. An experimental program has been established based on selected mix designs to study their main properties. The differences between both structuration processes were determined through a physicochemical study (XRD, NMR). They were correlated to the macroscopic phenomena observed at early age. An optimization of the mixtures was carried to satisfy the application criteria and define the parameters controlling the rheological and mechanical behavior of the grouts. Using a micromechanical characterization and multiscale homogenization, a methodology has been designed to determine the elastic modulus of the materials.This can be used as a first tool to analyze the global mechanical behavior. Finally, the sensitivity to drying and exposure to acid environments was assessed
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Jevická, Lucie. "Příprava geopolymerních pojiv pro inhibici toxických prvků." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2011. http://www.nusl.cz/ntk/nusl-216747.
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This thesis deals with preparation of geopolymeric binders for inhibition of toxic elements, especially arsenic. It studies influence of content progress of different phases in prepared binders on leachability of As during the setting. The aim of this study is to determine the type of inhibition or the cause of leachability of As in prepared binders respectively. Fly ash from high-temperature coal combustion, slag, cement kiln dust and sodium hydroxide solution were used for experimental works. FT-IR, TG-DTA, XRD analyses after different hydration times were used. The leachates were analyzed by ICP-MS. Calorimetric measurements of tested mixtures fresh pastes were implemented to learn about setting process. Hardened binder specimens were tested for bending and compressive strength.
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Komosná, Kateřina. "Studium mechanismu působení přísad redukující smrštění v alkalicky aktivovaných materiálech." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2017. http://www.nusl.cz/ntk/nusl-295703.
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This thesis is focused on the principles of behavior of shrinkage reducing agents (SRA) in alkali-activated materials based on blast furnace slag. The main focus of this work is selecting the most suitable admixture based on experiments, by which will be achieved through minimal shrinkage and will have negative effect on the properties of alkali-activated blast furnace slag at the same time. In experimental section of this work, the surface tension as individual additives as their mixtures with pore solution were measured primarily. Then the testing samples composed of blast furnace slag, water glass and addition of SRA were prepared. Of these samples was measured shrinkage and weight loss. Moreover, their mechanical properties such as flexural and compressive strength were monitored. Next, the beginning and the end of solidification was studied using the Vicat device and last but not least workability. The hydration process of alkali-activated materials with SRA was measured calorimetrically. Finally the microstructure in prepared samples was observed using scanning electron microscopy (SEM-EDS) and the total porosity was determined by mercury porosimeter.
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Citeroni, Chiara. "Alkali-activated expanded lightweight aggregates for the production of special asphalt concretes." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
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La presente tesi sperimentale si focalizza sulla produzione e successiva analisi, tramite test prescritti dalla normativa europea, di conglomerati bituminosi costituiti da aggregati leggeri che vadano a sostituire il 12% degli aggregati naturali, presenti in un tipico strato d’usura.
Questi aggregati leggeri sono stati originati partendo da due differenti polveri di scarto ad attivazione alcalina, quali polvere di basalto e bentonite esausta impiegati come principali precursori. Infatti, l’utilizzo di materiali di riciclo come prodotti sostenibili desta molto interesse nell’ambito ingegneristico, nello specifico in applicazioni su pavimentazioni stradali, in quanto essi possono rappresentare un modo per risparmiare energia e ridurre gli impatti ambientali.
Lo studio sperimentale si pone come ulteriore obiettivo la comparazione dei materiali leggeri sopracitati con l’argilla espansa, in modo da comprovare la loro efficacia e poterli considerare degli ottimi e più sostenibili sostituti.
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Vijayan, Vineesh. "Recycling alkali-activated powders for the production of lightweight aggregates for pavement applications." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
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The objective of this thesis is to create an innovative approach to the development of flexible pavements with the use of synthetic aggregates for the production of porous layers. The synthetic aggregates are produced by the alkali-activation process. The potential application of artificial aggregates in the pavement, paves a way to reduce the use of natural materials to certain extends. This also helps to utilize the increasing growth of waste by-products generated from different kinds of industries. Furthermore, in this research the conventional Bitumen for asphalt concrete was substituted with a transparent binder. Hence this will hope to decrease the impact of carbon dioxide and carbon monoxide which are emitted from the production of traditional mixtures with Bitumen in the road industry.
The first part of experimental phase includes the recipe of making the geopolymer aggregates. The precursors concerned with this production are basalt powder and metakaolin. These powders are activated by the mixture of reagents such as Sodium hydroxide and Sodium Silicate. After discovering the optimum percentage of each precursors and solid-liquid ratio, the productions of synthetic lightweight aggregates start.
The next experimental phase involves the Mix design and characterization of a porous mixture. In this part, it has been decided to replace the natural white aggregates by 21% with the synthetic lightweight aggregates to form a semi-porous pavement design as per the European Standards. This design also replaces the traditional bitumen with a transparent binder named ‘EVIzero-28’ which is a synthetic binder used to produce eco-friendly asphalt. After the selection of mix design, the samples are produced to find out the optimum percentage of transparent binder content. Once it gets, then the samples are prepared for the further experimental phases like testing as per European Standards.
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Ávila, Tainara Cristina. "Estudo da utilização da mistura de cinza da casca de arroz com hidróxido de sódio na produção de argamassas ativadas alcalinamente /." Ilha Solteira, 2018. http://hdl.handle.net/11449/180872.
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Orientador: José Luiz Pinheiro MelgesResumo: Atualmente, é vasta a quantidade de materiais estudados com potencial de substituir o cimento Portland em matrizes cimentícias, uma vez que a produção do mesmo é responsável pela emissão de grande quantidade de CO2, o que contribui drasticamente para o efeito estufa. Nesse contexto, os aglomerantes ativados alcalinamente são materiais que prometem qualidades similares ou superiores àqueles à base de cimento, porém produzidos com elementos menos agressivos ao meio ambiente. Neste trabalho, é realizado o estudo da aplicação de Cinza da Casca de Arroz (CCA) com Hidróxido de Sódio (NaOH) na produção de solução alcalina, para ativação do metacaulim, material este que já possui resultados positivos quando ativado com silicato de sódio, e outros ativadores obtidos comercialmente. A solução de CCA-NaOH é utilizada como substituta do silicato de sódio comercial, uma vez que, além de utilizar um resíduo em sua produção, dando a ele uma destinação adequada, observa-se uma significativa economia de energia, já que a produção de silicato de sódio demanda uma grande quantidade de energia para sua obtenção. Para que a solução de CCA-NaOH apresente potencial de ativar o metacaulim, é necessário manter tais materiais, por 24h em meio térmico, para que ocorra a dissolução da sílica do CCA. Utilizando-se a composição CCA-NaOH, foram elaborados 5 traços de argamassa com relações molares SiO2/NaOH iguais a 0.0; 0.4; 0.8; 1.2 e 1.6. Também foram elaborados outros 5 traços com as mesmas relações mo... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Nowadays, the amount of studied materials with the potential to replace Portland cement in cementitious matrices is extensive, since its production is responsible for the emission of a large amount of CO2, which contributes drastically to the greenhouse effect. In this context, alkali-activated binders are materials that promise qualities similar or superior to those based on cement, but produced with elements that are less aggressive to the environment. In this work, Rice Husk Ash (RHA) with sodium hydroxide (NaOH) are used to produce an alkaline solution for the activation of metakaolin, which has already positive results when activated with sodium silicate or others commercially available activators. The RHA-NaOH solution is used as a substitute for commercial sodium silicate, once in addition to use a residue in its production, giving it an adequate disposal, it works with the fact of saving energy, since the production of silicate of sodium consumes a large amount of energy for its obtainment. In order for the RHA-NaOH solution to have the potential to activate metakaolin, it is necessary to keep such materials for 24 hours in a thermal container in order to dissolve the silica from the CCA. Using the RHA-NaOH solution, 5 mixtures of mortar were prepared with SiO2 / NaOH molar ratios equal to 0.0; 0.4, 0.8, 1.2 and 1.6. Another 5 mixtures were prepared with the same molar ratios, but this time using commercial sodium silicate for comparison purposes. It was observed the ... (Complete abstract click electronic access below)
Mestre
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Russkykh, Kostyantyn. "Vliv typu aktivátoru na reologii a povrchovou chemii alkalicky aktivované strusky." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2021. http://www.nusl.cz/ntk/nusl-449703.
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V této závěrečné práci bylo popsáno časné reologické chování alkalicky aktivované strusky, anorganického materiálu, který vzniká aktivací mleté granulované vysokopecní strusky alkalickým roztokem. Vliv typu aktivačního roztoku (hydroxidů, křemičitanů a uhličitanů) a jeho koncentrace na časné reologické parametry byl zkoumán pomocí amplitudových oscilačních měření. Bylo pozorováno, že typ aktivátoru je hlavním faktorem ovlivňujícím reologické chování alkalicky aktivované strusky. Dále bylo pozorováno, že aktivátory na bázi draslíku vedou ke slabší struktuře (nižší mez kluzu, mez toku a nižší hodnoty viskoelastických modulů) oproti použití aktivátorů na bázi sodíku. To lze vysvětlit rozdíly ve velikosti alkalických iontů. Na rozdíl od ostatních aktivátorů křemičitany způsobovaly zvýšení ztrátového faktoru, přičemž vykazovaly spíše kapalné chování. Z výsledků vyplynulo, že většina aktivátorů má tzv. kritickou hodnotu koncentrace, po jejímž dosažení mají reologické vlastnosti vzorků tendenci se měnit s rostoucí koncentrací. Získané výsledky korelovaly s výstupy zeta potenciálu.
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OCCHIPINTI, ROBERTA. "Valorization of secondary raw materials through alkali activation: study of binders based on sulfate-bearing clay and Pietra Serena sewage sludge." Doctoral thesis, Università degli studi di Pavia, 2018. http://hdl.handle.net/11571/1214865.
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Alkali activation is the chemical process through which precursors sufficiently rich in reactive silica and alumina and with amorphous or vitreous structures interact with a strongly alkaline medium to give rise, under mild processing conditions, to materials with good binding and cementing properties. Nowadays, Alkali Activated Materials (AAMs) have emerged as alternative to traditional construction materials, such as mortars or Ordinary Portland Cement (OPC), with the aim to become primary components in the development of environmentally sustainable building products.
This Ph.D. study has assessed the possibility to valorize through the alkali activation process two different Italian raw materials: a sulfate-bearing kaolinitic clay and Pietra Serena sewage sludge for the synthesis of AAMs. The former is currently unused resource and the latter simply discarded in landfills. Considered the need to have a long-term, secure supply of the materials for the cement production, different raw materials need to be evaluated. The results are promising, as both resources demonstrated to be reactive in the alkali activation process giving an aluminosilicate gel binder as main product.
Beside the first more applicative objective, a second, fundamental objective of this thesis has underpinned the study of the effect of the sulfate deriving from L02-K clay in the alkali activation process.
In the system Na2O–Al2O3–SiO2–H2O(–SO4), achieved by activating sulfate-bearing kaolinitic clay with sodium silicate, the amorphous N-A-S-H gel is the main reaction product in presence or in absence of sulfate ions. In all samples containing sulfate, no new crystalline phases have been found apart from thenardite, which forms as by-product after setting time. It is leached in water, but part of sulfate remains in the samples. These findings indicate that sulfate may be trapped in amorphous insoluble phases, likely the aluminosilicate gel itself or nanozeolites. The amount of unsoluble sulfate is higher in samples with the highest SiO2/Al2O3 ratio.
The system Na2O–CaO–Al2O3–SiO2–H2O–SO4 has been achieved by blending sulfate-bearing kaolinitic clay and residual sludge of Pietra Serena cultivation. The use of heat-treated sludge, sPS_800, add reactive CaO to the investigated system. The behavior of sPS_800 is similar to pozzolanic cement, the interaction between the different precursors occurs and gives rise to a mixture of N,(C)-A-S-H / C-(A)-S-H gels, similar to those produced in so-called mixed alkali cements or hybrid cements. In this system, calcium sulfo-aluminate compounds such as U-phase or ettringite are formed depending on the alkalinity of the activation solution. Sulfate-bearing cancrinite has been found in all samples prepared at 8M and cured at 85°C. Formation of cancrinite and ettringite is considered desirable, as both structures can trap sulfate, in fact they can be used for nuclear waste encapsulation via cementation.
The crystalline products of the reaction of the two kaolinitic clays with alkali have been evaluated. Zeolitation of Sl-K was carried out under molten condition in the absence or presence of sulfate by adding thenardite to the mixture. In the former case, it gave A and Y zeolite, as expected. On the other hand, when sulfate is contained in the reacting mixtures sulfate bearing cancrinites are the main reaction products.
Therefore, it can be concluded that sulfate ion could drive the nucleation and precipitation of CAN-type zeolites, likely acting as a ‘structure director’ during crystallization. From these findings, one may speculate that sulfate may have the same effect also in alkali activation process and that the local structure of the N-A-S-H gel may resemble that of cancrinite. A possible continuation of this work could focus on the experimental verification of this hypothesis.
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Oberlink, Anne Elizabeth. "NON-PORTLAND CEMENT ACTIVATION OF BLAST FURNACE SLAG." UKnowledge, 2010. http://uknowledge.uky.edu/gradschool_theses/25.
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The purpose of this project was to produce a “greener” cement from granulated ground blast furnace slag (GGBS) using non-Portland cement activation. By eventually developing “greener” cement, the ultimate goal of this research project would be to reduce the amount of Portland cement used in concrete, therefore reducing the amount of carbon dioxide emitted into the atmosphere during cement production.
This research studies the behavior of mineral binders that do not contain Portland cement but instead comprise GGBS activated by calcium compounds or fluidized bed combustion (FBC) bottom ash. The information described in this paper was collected from experiments including calorimetry, which is a measure of the release of heat from a particular reaction, the determination of activation energy of cement hydration, mechanical strength determination, and pH measurement and identification of crystalline phases using X-ray diffraction (XRD).
The results indicated that it is possible to produce alkali-activated binders with incorporated slag, and bottom ash, which have mechanical properties similar to ordinary Portland cement (OPC). It was determined that the binder systems can incorporate up to 40% bottom ash without any major influence on binder quality. These are positive results in the search for “greener cement”.
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Tole, Ilda. "Mechanical activation of clay : a novel route to sustainable cementitious binders." Licentiate thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-76362.
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EU Sustainable Development Strategy planned to achieve improvement of life-quality by promoting sustainable production and consumption of raw materials. On November 2018, EU Commission presented a long-term strategy, aiming among others a climate-neutral economy by 2050. Cement production is contributing to 6-10% of the anthropogenic CO2 emissions. Thus, several strategies for total or partial replacement of Portland cement in concrete production have been developed. The use of supplementary cementitious materials (SCM) and alkali-activated materials (AAM) is considered the most efficient countermeasure to diminish CO2 emissions. The broadening of knowledge with particular attention to the sustainable goals is the primary requirement to be fulfilled when novel materials are investigated. This study aims to develop a novel clay-based binder that can be used as a sustainable alternative to produce SCM as well as AAM. Clay is a commonly occurring material, with large deposits worldwide. However, natural clay has a low reactivity and various compositions, depending, e.g. on the weathering conditions. The present research aims exactly at enhancing the reactivity of natural clays occurring in Sweden subjecting them to mechanical activation in a planetary ball mill. Ball milling (BM) is considered a clean technology able to enhance the reactivity of crystalline materials without resorting to high processing temperatures or additional chemicals. BM was able to induce amorphization in clay minerals and to transform the layered platy morphology to spherical shape particles. The efficiency of the process was strictly related to the used process parameters. Higher ball to processed powder (B/P) ratio, longer time of grinding and higher grinding speeds increased the degree of the obtained amorphization. However, an undesired extensive caking and agglomeration occurred in certain setups. The potential of activated clay as a SCM was investigated in specific case studies. The measured compressive strength results showed a direct correlation between the enhanced amorphization degree of the mechanically activated clay and the increased strength values. The pozzolanic activity was induced and enhanced after the mechanical activation of the clay. The reactivity was assessed by the strength activity index (SAI). Furthermore, preliminary tests have shown that the alkali activation of the processed clays produced solidified matrixes with considerable strength.
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Bartoňová, Pavla. "Příprava a vlastnosti ryzích geopolymerů." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2009. http://www.nusl.cz/ntk/nusl-216465.
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Brýdl, David. "Dřevokompozity s alkalicky aktivovanou popílkovou matricí." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2012. http://www.nusl.cz/ntk/nusl-225718.
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This thesis examines the possibility of creating composite mainly from waste materials. The matrix of this composite was prepared from fly ash type F, which was activated by sodium water glass. Wood chips were used as a filler. This thesis includes theoretical and experimental parts. The theoretical part deals with the most important issues of wood composites with an inorganic matrix as well as basic components of investigated composite, ie alkaline activated fly ash and wood. In the experimental part, the fly ash pastes were prepared, from which the most suitable mixture was chosen for the composite preparation. Properties of wood composite with alkali activated fly ash matrix were investigated depending on the dose of wood chips.
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Kejík, Pavel. "Low-Cost Filtration Barriers for Ultrafine Particles Separation." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-401605.
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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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Shearer, Christopher R. "The productive reuse of coal, biomass and co-fired fly ash." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/52298.
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Stricter greenhouse gas emission limits and renewable energy requirements are expected to further increase the worldwide practices of firing biomass and co-firing biomass with coal, which are both considered more sustainable energy sources than coal-only combustion. Reuse options for the by-products of these processes -biomass ash and co-fired fly ash -remain limited. Therefore, this research examines their use as supplementary cementitious materials (SCMs) in concrete and as precursors for alkali-activated geopolymers.
Toward their potential use as an SCM, after characterizing these ashes assessing their compliance with ASTM C618 requirements, their impact on early-age hydration kinetics, rheology, setting time and permeability was assessed. Furthermore, the pozzolanic reactivity and the microstructural and hydrated phase development of the cement-ash samples were analyzed. The results show that a wood biomass ash sample was not satisfactory for use as an SCM. On the other hand, the findings demonstrate that co-fired fly ashes can significantly improve the strength and durability properties of concrete compared to ordinary portland cement, in part due to their pozzolanicity. Thus, it is recommended that the ASTM C618 standard be modified to permit co-fired fly ash sources that meet existing requirements and any additional requirements deemed necessary to ensure their satisfactory performance when used in concrete.
Toward their potential use in geopolymers, this study characterized the early-age reaction kinetics and rheological behavior of these materials, showing that their exothermic reactivity, plastic viscosity and yield stress are significantly influenced by the activator solution chemistry and other characteristics of the ash. Two co-fired fly ashes were successfully polymerized, with compressive strengths generally highest for ashes activated with solutions with a molar ratio of SiO₂/(Na₂O + K₂O) = 1. The results show that geopolymerization is a viable beneficial reuse for these emerging by-products. Further characterization of these materials by scanning transmission X-ray microscopy analysis revealed the heterogeneity of the aluminosilicate phase composition of the co-fired fly ash geopolymer gel at the nano- to micro-scale.
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Kalina, Lukáš. "Syntéza aluminátosilikátových systémů na bázi geopolymerů orientovaná na využívání sekundárních surovin." Doctoral thesis, Vysoké učení technické v Brně. Fakulta chemická, 2011. http://www.nusl.cz/ntk/nusl-233335.
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Portland cement-based products are the most commonly used building materials. However, it is well known that the production of OPC not only consumes a significant amount of natural resources and energy but also releases high quantity of carbon dioxide (CO2) to the atmosphere. Purpose of this work is to develop new cementitious material similar to Portland cement-based concrete, which is convenient in terms of energy and is environmental-friendly at once. This work presents preparation, composition and properties of inorganic aluminosilicate polymer, called geopolymer, synthesized from blast furnace slag and fly ash, activated by sodium hydroxide and cement kiln dust. Study of the microstructure was based on SEM-EDX-WDX, TG-DTA-EGA and XRD analysis.
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Suchý, Rostislav. "Studium karbonatace alkalicky aktivovaných systémů." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2016. http://www.nusl.cz/ntk/nusl-240541.
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The carbonation of the building materials based on the ordinary Portland cement is relatively well-known and extensively studied phenomenon. Conversely mechanism, reaction products and factors affecting the carbonation of the alkali activated materials are still not sufficiently clarified. In this work, the progression of the carbonation of the alkali activated materials under different conditions was investigated. The reaction products and the microstructural changes were determined by XRD respectively SEM-EDX analysis. The corrosive conditions due to the decreasing of the pH of the binders by the carbonation were observed by XPS analysis of the steel fibers. The carbonation of the alkali activated samples was compared with the reference samples based on the Portland composite cement. Besides these analyzes, the mechanical properties of the binders were monitored.
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Kiventerä, J. (Jenni). "Stabilization of sulphidic mine tailings by different treatment methods:heavy metals and sulphate immobilization." Doctoral thesis, Oulun yliopisto, 2019. http://urn.fi/urn:isbn:9789526223964.
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Abstract Millions of tons of mine tailings are generated worldwide annually. Since many valuable metals such as Ag, Cu, Pb, Zn, Au and Ni are usually incorporated into sulphidic minerals, a large proportion of the tailings generated contain high amounts of sulphates and heavy metals. Some of these tailings are used as paste backfill material at mining sites, but large amounts are still being deposited into the tailings dams under water coverage. Sulphidic minerals are stable underground but after mining of the ore and several processing steps these minerals can be oxidized when they come into contact with water and air. This oxidation generates acid and thus reduces the pH of the surrounding environment. Furthermore, the heavy metals present in the mine tailings can be leached into the environment. This phenomenon, called Acid Mine Drainage (AMD), is one of the most critical environmental issues related to the management of sulphidic-rich tailings. Since AMD generation can still occur hundreds of years after closure of the mine, the mine tailings need stable, sustainable and economically viable management methods in order to prevent AMD production in the long term. The aim of this PhD thesis was to study various solidification/stabilization (S/S) methods for the immobilization of sulphidic mine tailings. The main focus was to develop a suitable chemical environment for achieving effective heavy metal (mainly arsenic) and sulphate immobilization while simultaneously ensuring good mechanical properties. Three treatment methods were tested: alkali activation, stabilization using hydrated lime (Ca(OH)2) and blast furnace slag (GBFS), and calcium sulphoaluminate-belite (CSAB) cement stabilization. The mine tailings used in this study contained large amounts of sulphates and heavy metals such as Cr, Cu, Ni, Mn, Zn, V and As. The leaching of arsenic and sulphates from powdered tailings exceeded the legal limits for regular and inert waste. All treatment methods were found to generate a hardened matrix that was suitable for use as a backfilling or construction material, but the calcium-based binding system was the most suitable for effective immobilization of all the heavy metals (including arsenic) and the sulphates. Precipitation in the form of calcium sulphates/calcium arsenate and the formation of ettringite are the main stabilization methods employed in calcium-based stabilization/solidification (S/S) systems. Some evidence of physical encapsulation occurring simultaneously with chemical stabilization was noted. These results can be exploited further to develop more sustainable mine tailing management systems for use in the future. The tailings could be stored in a dry landfill area instead of in tailing dams, and in this way a long-term decrease in AMD generation could be achieved, together with a high potential for recyclingTiivistelmä Monet arvometallit kuten kulta, kupari ja nikkeli ovat sitoutuneena sulfidipitoisiin mineraaleihin. Louhittaessa ja rikastettaessa näitä sulfidimineraaleja syntyy miljoonia tonneja sulfidipitoisia rikastushiekkoja vuosittain. Rikastushiekat voivat sisältää myös runsaasti erilaisia raskasmetalleja. Osa rikastushiekoista hyödynnetään kaivostäytössä, mutta suurin osa rikastushiekoista läjitetään edelleen ympäristöön rikastushiekka-altaisiin veden alle. Kun sulfidipitoinen malmi kaivetaan ja käsitellään, sulfidiset mineraalit hapettuvat ollessaan kosketuksissa veden ja hapen kanssa. Hapettuessaan ne muodostavat rikkihappoa, laskien ympäristön pH:ta jolloin useimmat raskasmetallit liukenevat ympäristöön. Muodostuvia happamia kaivosvesiä voi syntyä vielä pitkään kaivoksen sulkemisen jälkeen ja ovat näin ollen yksi suurimmista kaivosteollisuuteen liittyvistä ympäristöongelmista. Lisäksi suuret rikastushiekka-altaat voivat aiheuttaa vaaraa myös ihmisille, mikäli altaan rakenteet pettävät. Rikastushiekkojen kestäviä ja ympäristöystävällisiä varastointimenetelmiä täytyy kehittää, jotta näitä ongelmia voidaan tulevaisuudessa ehkäistä. Tässä työssä tutkittiin menetelmiä, joilla kultakaivoksella syntyvät sulfidipitoiset vaaralliseksi jätteeksi luokitellut rikastushiekat saataisiin stabiloitua tehokkaasti. Työssä keskityttiin kolmeen erilaiseen menetelmään: alkali-aktivointiin, stabilointiin kalsiumhydroksidin ja masuunikuonan avulla ja stabilointiin CSAB sementin avulla. Valmistettujen materiaalien mekaanisia ja kemiallisia ominaisuuksia arvioitiin. Tavoitteena oli ymmärtää, miten eri menetelmät soveltuvat raskasmetallien (erityisesti arseenin) ja sulfaattien sitoutumiseen ja mikä on eri komponenttien rooli reaktioissa. Alkali-aktivoimalla rikastushiekkaa sopivan sidosaineen kanssa saavutettiin hyvät mekaaniset ominaisuudet ja useimmat haitta-aineet sitoutuivat materiaaliin. Ongelmia aiheuttivat edelleen sulfaatit ja arseeni. Kalsiumpohjaiset menetelmät sitoivat raskasmetallit (myös arseenin) ja sulfaatit tehokkaimmin. Sulfaatit ja arseeni saostuivat muodostaen niukkaliukoisia komponentteja kalsiumin kanssa. Samanaikaisesti rakenteeseen muodostui ettringiittiä, jolla on tutkitusti hyvä kyky sitoa erilaisia raskasmetalleja rakenteeseensa. Raskasmetallit myös kapseloituivat rakenteen sisään. Työn tuloksia voidaan hyödyntää, kehitettäessä rikastushiekkojen turvallista varastointia. Kun materiaalille saavutetaan riittävän hyvä lujuus ja kemiallinen stabiilius, rikastushiekat voitaisiin läjittää tulevaisuudessa kuivalle maalle altaan sijaan. Näin vältyttäisiin rikastushiekka-altaiden rakentamiselta ja voitaisiin vähentää happamien kaivosvesien muodostumista pitkällä ajanjaksolla. Saavutettujen tulosten perusteella rikastushiekkoja voidaan mahdollisesti tulevaisuudessa hyödyntää myös erilaisissa betonin tapaisissa rakennusmateriaaleissa
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Belleggia, Marco Maria. "Synthesis and characterization of artificial aggregates and their potential applications in road construction." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016.
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L’obiettivo del progetto è stato quello di realizzare ed analizzare aggregati artificiali creati attraverso geopolimerizzazione e macro-incapsulazione di paraffina in aggregati leggeri espansi, discutendo i loro possibili impieghi nelle pavimentazioni stradali. Dopo un'accurata calibrazione delle miscele geopolimeriche, sono stati realizzati degli aggregati artificiali, in seguito caratterizzati in accordo con la norma UNI EN 10343, con l'intento di sostituire materiali stradali vergini. Contemporaneamente, sono stati prodotti aggregati leggeri impregnati di paraffina (PCM), in grado di cambiare fase una volta raggiunti all'incirca i 3 °C, e successivamente rivestiti da due strati di resina poliestere e
polvere di granito, denominati PLA: sfruttandone le proprietà termiche, si è valutato il loro possibile utilizzo come soluzione anti-icing. L’ultima fase della ricerca è stata incentrata nella realizzazione di aggregati geopolimerici espansi e molto porosi che potessero contenere una elevata quantità di PCM, sostituendo l'argilla espansa utilizzata nella produzione degli PLA.
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Georgakopoulos, Evangelos D. "Iron and steel slag valorization through carbonation and supplementary processes." Thesis, Cranfield University, 2016. http://dspace.lib.cranfield.ac.uk/handle/1826/12323.
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Alkaline industrial wastes are considered potential resources for the mitigation of CO2 emissions by simultaneously capturing and sequestering CO2 through mineralization. Mineralization safely and permanently stores CO2 through its reaction with alkaline earth metals. Apart from natural formations, these elements can also be found in a variety of abundantly available industrial wastes that have high reactivity with CO2, and that are generated close to the emission point-sources. Apparently, it is the applicability and marketability of the carbonated products that define to a great extent the efficiency and viability of the particular process as a point source CO2 mitigation measure. This project investigates the valorization of iron- and steel-making slags through methods incorporating the carbonation of the material, in order to achieve the sequestration of sufficient amounts of CO2 in parallel with the formation of valuable and marketable products. Iron- and steel-manufacturing slags were selected as the most suitable industrial byproducts for the purposes of this research, due to their high production amounts and notable carbonation capacities. The same criteria (production amount and carbonation capacity) were also used for the selection of the iron- and steel-making slag types that are more suitable to the scope of this work. Specifically for the determination of the slag types with the most promising carbonation capacities, the maximum carbonation conversions resulting from recent publications related to the influence of process parameters on the conversion extent of iron- and steel-manufacturing slags, were directly compared to each other using a new index, the Carbonation Weathering Rate, which normalizes the results based on particle size and reaction duration. Among the several iron- and steel-manufacturing slags, basic oxygen furnace (BOF) and blast furnace (BF) slags were found to combine both high production volumes and significant affinity to carbonation. In the context of this research, two different procedures aiming to the formation of value added materials with satisfactory CO2 uptakes were investigated as potential BF and BOF slags valorization methods. In them, carbonation was combined either with granulation and alkali activation (BOF slag), or with hydrothermal conversion (BF slag). Both treatments seemed to be effective and returned encouraging results by managing to store sufficient amounts of CO2 and generating materials with promising qualities. In particular, the performance of the granulation-carbonation of BOF slag as a method leading to the production of secondary aggregates and the sequestration of notable amounts of CO2 in a solid and stable form, was evaluated in this work. For comparison purposes, the material was also subjected to single granulation tests under ambient conditions. In an effort to improve the mechanical properties of the finally synthesized products, apart from water, a mixture of sodium hydroxide and sodium silicate was also tested as a binding agent in both of the employed processes. According to the results, the granules produced after the alkali activation of the material were characterized by remarkably greater particle sizes (from 1 to 5 mm) compared to that of the as received material (0.2 mm), and by enhanced mechanical properties, which in some cases appeared to be adequate for their use as aggregates in construction applications. The maximum CO2 uptake was 40 g CO2/kg of slag and it was achieved after 60 minutes of the combined treatment of alkali activated BOF slag. Regarding the environmental behavior of the synthesized granules, increased levels of Cr and V leaching were noticed from the granules generated by the combination of granulation-carbonation with alkali activation. Nevertheless, the combination of granulation with alkali activation or that of granulation with carbonation were found not to worsen, if not to improve, the leaching behaviour of the granules with regards to the untreated BOF slag. The formation of a zeolitic material with notable heavy metal adsorption capacity, through the hydrothermal conversion of the solid residues resulting from the calcium- extraction stage of the indirect carbonation of BF slag, was also investigated in this project. To this end, calcium was selectively extracted from the slag by leaching, using acetic acid of specific concentration (2 M) as the extraction agent. The residual solids resulting from the filtration of the generated slurry were subsequently subjected to hydrothermal conversion in caustic solution of two different compositions (NaOH of 0.5 M and 2 M). Due to the presence of calcium acetate in the composition of the solid residues, as a result of their inadequate washing, only the hydrothermal conversion attempted using the sodium hydroxide solution of higher concentration (2 M) managed to turn the amorphous slag into a crystalline material, mainly composed by a zeolitic mineral phase (detected by XRD), namely, analcime (NaAlSi2O6·H2O), and tobermorite (Ca5(OH)2Si6O16·4H2O). Finally, the heavy metal adsorption capacity of the particular material was assessed using Ni2+ as the metal for investigation. Three different adsorption models were used for the characterization of the adsorption process, namely Langmuir, Freundlich and Temkin models. Langmuir and Temkin isotherms were found to better describe the process, compared to Freundlich model. Based on the ability of the particular material to adsorb Ni2+ as reported from batch adsorption experiments and ICP-OES analysis, and the maximum monolayer adsorption capacity (Q0 = 11.51 mg/g) as determined by the Langmuir model, the finally synthesized product can potentially be used in wastewater treatment or environmental remediation applications.
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Fialová, Barbora. "Rehydratace alkalicky aktivované strusky po vysokoteplotním namáhání." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2016. http://www.nusl.cz/ntk/nusl-239940.
Full textAbstract:
Ground granulated blast furnace slag is a by-product of the steel industry and is often used in combination with ordinary Portland cement as a binder in concrete. When concrete is exposed to high temperatures, physical and chemical transformations lead to significant loss of mechanical properties. This study aims to investigate the effect of high temperatures and rehydration on the mechanical properties, microstructure and phase composition of alkali activated slag. The results of the research could make an important contribution to decisions made concerning the reconstruction of structures affected by fire. In suitable cases it would be possible to regenerate parts of a structure instead of totally rebuilding it.
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Indra, Ivo. "Kompozitní materiály na bázi alkalicky aktivované vysokopecní strusky s přídavkem elektrárenských popílků." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2010. http://www.nusl.cz/ntk/nusl-216595.
Full textAbstract:
This thesis concerns on substitution of blast furnace slag or its part with fly ash in alkali-activated systems based on aluminosilikates. Classic, fluid bottom and fluid filter fly ashes will be tested. The goal is to prepare geopolymer with required mechanical properties, but with maximal admixture of alternative raw materials. In composites with substitutioned slag or its part the thesis focuses mainly on workabilityof fresh mixture, pressure and bending strenght. Use of secondary raw materials has advantages in the economic point of view and it´s friendly to enviroment, too.
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Novák, Václav. "Vliv velikosti částic odpadního skla na vlastnosti alkalicky aktivovaných aluminosilikátových kompozitů." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2019. http://www.nusl.cz/ntk/nusl-392355.
Full textAbstract:
The diploma thesis is focused on the use of the waste glass with different fineness on alkali - activated composites, mainly based on slag and fly ash. The theoretical part is focused on materials that are most used for alkaline activation - slag, fly ash and their composites with waste glass. The theoretical part also deals with the alkaline activation of composites from these materials and the factors that influences the microstructure and properties of these composites. In the experimental part were prepared composites from slag and fly ash with a waste glass as substitute. These composites then have been examined on mechanical properties and microstructure, also how different fineness of glass influences these properties. Then it will be decided whether it is economically advantageous grinding waste glass to finer fractions
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Halasová, Kristýna. "Vliv přísad na vlastnosti metakaolinového geopolymeru." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2017. http://www.nusl.cz/ntk/nusl-265558.
Full textAbstract:
Geopolymers are amorphous to semi-crystalline aluminosilicate polymers which are formed from inorganic polycondensation reaction of a solid aluminosilicate precursor with an alkaline sodium hydroxide or silicate. The resulting materials exhibit high durability, resistance to aggressive environments, high temperature resistance and many other properties that make them have received much attention in recent years, not only in construction. This thesis describes the influence of additives commonly used in concrete and mortar (water reducing, superplasticizer, air-entraining, foamer and defoamer, anti-shrinkage, stabilization) on the behavior of metakaolin in geopolymer fresh and hardened state. It describes metakaolin geopolymer effect on rheological properties of fresh mixtures, compressive strength and flexural strength after 28 days and a density in the fresh and hardened state.
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SGARLATA, CATERINA. "Studio di formulazioni di geopolimeri a basso impatto ambientale." Doctoral thesis, Università degli studi di Modena e Reggio Emilia, 2022. http://hdl.handle.net/11380/1270082.
Full textAbstract:
Lo scopo di questo progetto di tesi è lo studio e lo sviluppo di nuovi materiali da costruzione ad alte prestazioni, denominati geopolimeri, più sostenibili di quelli già ampiamente presenti sul mercato (come il cemento Portland), ottenuti dal recupero di materiali di scarto industriale nel rispetto dell'ambiente e lo sviluppo sostenibile.
L'obiettivo principale è lo sfruttamento di varie tipologie di rifiuti argillosi (argille halloisitiche, caolinitiche e smectitiche) provenienti da operazioni minerarie, come potenziali precursori di materiali geopolimerici in un’ottica di economia circolare degli scarti da operazioni di estrazione mineraria.
Sono stati approfonditi gli effetti delle principali variabili sperimentali, come la tipologia di matrice allumino silicatica, le condizioni e la temperatura dei tempi di presa, la composizione della soluzione attivante e i rapporti molari dei cationi Si:Al sul processo di geopolimerizzazione con la finalità ultima di ottenere le migliori proprietà dei prodotti finali.
È stata studiata anche l'influenza della temperatura di calcinazione sulla reattività delle polveri allumino silicatiche e sulle proprietà dei materiali finali. Inizialmente il mix design delle formulazioni è stato focalizzato sull’utilizzo delle argille tal quali senza alcun pretrattamento di calcinazione. Successivamente sono state studiate le formulazioni con le argille calcinate, trattate a diverse temperature tra i 400-650°C.
In seguito, è stata valutata l'aggiunta nel mix design della matrice di argilla, di basse percentuali di fillers reattivi, in particolare una sabbia ottenuta da un processo di lavaggio dell'argilla, una polvere di scarto di vetro di campana e un metacaolino commerciale (MK), per migliorare le proprietà chimico-fisiche e il grado di consolidamento dei materiali. Infatti, queste argille spesso non sono sufficientemente reattive per ottenere da sole formulazioni chimicamente stabili con proprietà meccaniche accettabili ma richiedono l'aggiunta di cariche reattive.
Gli attivatori alcalini utilizzati nelle formulazioni sono NaOH 8M e Na2SiO3. I campioni sono stati realizzati a temperatura ambiente, ad eccezione di una serie di campioni realizzati con argilla non trattata e reticolati in condizioni di temperatura e umidità controllate.
I campioni ottenuti, sono stati caratterizzati in termini di microstruttura e resistenza chimica e meccanica. La stabilità chimica è stata determinata con misure di pH e di conducibilità ionica dell'acqua di lisciviazione e la perdita in peso. Le variazioni sulla microstruttura sono state osservate con analisi di densità, XRD e SEM e testate le prestazioni meccaniche con la resistenza alla compressione. I tempi di presa del mix geopolimerico è stato studiato con il test con ago Vicat.
Da questo studio sono state ottenute buone formulazioni di materiali ad alte prestazioni, consolidati a temperatura ambiente entro le 24-48h, con resistenza a compressione di circa 20-30 MPa. Sulla formulazione migliore sono state effettuate anche delle caratterizzazioni termiche e dilatometriche per valutarne la resistenza al riscaldamento.
In linea con l'approccio dell'Economia Circolare, questa attività di ricerca mostra un possibile percorso di valorizzazione per diverse tipologie di materiali di scarto minerario ampiamente disponibili per creare leganti alternativi con ridotto impatto ambientale. Il consolidamento proposto a temperatura ambiente tramite attivazione alcalina di soluzioni a basso costo contenenti Na mantentiene i costi in linea con materiali da costruzione economici. A parte la soluzione acquosa, la tecnologia proposta non prevede consumi idrici, non genera a sua volta rifiuti, chiudendo così il ciclo dell'economia verde con una proposta di produzione senza acqua e senza rifiuti.The aim of this research project is the study and development of new high-performance construction materials, namely geopolymers, more sustainable than those already widely on the market (such as Ordinary Portland Cement-OPC), obtained from the recovery of industrial waste materials, for an environmental protection and sustainable development. The exploitation of different kinds of clayey waste -halloysitic, kaolinitic and smectitic - from mining operations, as potential precursor of geopolymeric materials in the view of a circular economy of mines is the main goal of this study. The influence of the main experimental variables such as type of the aluminosilicate powder, curing condition and temperature, composition of activating solution and molar Si:Al cation ratios on the geopolymerization process were deepened to achieve the finest properties of the final products. The influence of the calcination temperature on the reactivity of the aluminosilicate powders and on the properties of the final products were investigated. The mix design of formulations started with the use of clays as received without any firing pre-treatment and it was continued with the use of calcined clays. The clays were thermally treated at the temperature of 400-650°C. Then, the addition of low percentages of reactive fillers, specifically a sand from a clay washing process, waste glass powder, and a commercial metakaolin (MK), into the mix design of waste clay-based materials was evaluated to improve the chemical-physical properties and the consolidation degree of the materials. In fact, these clays alone are often not sufficiently reactive to obtain chemically stable formulations with acceptable mechanical properties but require the addition of reactive fillers. The alkali activators used in the formulations are NaOH 8M and Na2SiO3. Samples were cured at room temperature, except for a particular set of samples made with untreated clay and cured in conditions of controlled temperatures and humidity. Samples obtained were characterized to evaluate the influence of synthesis parameters on the microstructure and chemical and mechanical resistance. The chemical stability was analysed with the pH and ionic conductivity of leachate water and weight loss. The comparison of setting times was evaluated with the Vicat needle test. The variations on the microstructure were observed with density, XRD and SEM analysis, and tested the mechanical performance with the compressive strength. From this study, good formulations of high-performance materials based on clayey waste, consolidated at room temperature during 24-48 h, with compressive strength of 20-30 MPa were obtained. Thermal and dilatometric characterizations were also carried out on the best formulations to assess their resistance to heating. In alignment with the Circular Economy approach, this research activity shows a possible route of valorisation for different typologies of mining waste materials widely available to create alternative binders with reduced environmental impact and good performances. Additionally, the room temperature consolidation via alkaline activation of low cost Na-bearing solutions is also proposed to keep costs in line with cheap building materials. Apart from the aqueous solution, the proposed technology has no-water consumption. It should also be noted that the proposed materials processing does not, in turn, generate waste, thus closing the loop of green economy circle with no-water and no-waste manufacturing proposal.
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Lisztwanová, Ewa. "Kompozitní materiály se silikátovou matricí do prostředí vysokých teplot." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2017. http://www.nusl.cz/ntk/nusl-265581.
Full textAbstract:
This thesis deals with the study and design of composite materials based on silica matrix suitable for extreme conditions, eg. for the repair of concrete structures with anticipated increased risk of fire. The theoretical part summarizes basic knowledge concerning the fire resistance of structures and the behavior of the composite system during extreme conditions. Theoretically oriented section also contains information on alkali-activated materials and their use in high temperature environments. Based on the evaluation of the theoretical part of the experiment were designed and tested different types of composite materials with increased content of raw materials from alternative sources. Laboratory research has been based on testing of basic physico-mechanical parameters including phase composition and microstructure of the proposed formulations before and after thermal exposure of 1200 ° C. Also considered was the effect of different cooling conditions.
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Řezník, Bohuslav. "Geopolymery na bázi elektrárenských popílků a cihelného střepu." Doctoral thesis, Vysoké učení technické v Brně. Fakulta stavební, 2014. http://www.nusl.cz/ntk/nusl-390250.
Full textAbstract:
In line with the current focus on utilizing side products of various production processes, this dissertation thesis analyzes the process of alkali activation of particular side products: fly ash and brick fragments. This activation produces geopolymeric materials widely used in civil engineering. The thesis aims to optimize the geopolymerization process so that the resulting geopolymer is both ecologically and economically viable. To that end, the thesis studies the course of geopolymeric reaction between the alkali activator and fly ash from: (i) the Chvaletice power plant, (ii) the Dětmarovice power plant, and (iii) biomass combustion, as well as (iv) fluid fly ash from the Hodonín power plant. All experiments of geopolymeric reaction have focused on the factors influencing the synthesis of geopolymers—that is: composition of the alkali activator, the ratio of alumino-silicate to the activator, and the impact of temperature on structure of the synthesized geopolymer. Further, the thesis analyzed the synthesized polymer’s microstructure, phase composition, resistance against corrosive conditions, and compressive strength, as well as mechanical-fracture properties of selected fly-ash geopolymers. The thesis finds that the most suitable for geopolymeric synthesis appears to be the fly ash from the Chvaletice power plant in which case the obtained geopolymers showed best properties in the studied areas. The fly ash from the Dětmarovice power plant, biomass fly ash, and fluid fly ash have failed to reach acceptable properties. Separately, the thesis studies the geopolymerization of brick body that could be suitable input for alkali activation. The geopolymers synthesized from brick fragments resulted in materials of supperior mechanical strength. A mixed use of fly ash and brick fragments failed to show a synergetic effect. Properties of the resulting geopolymers have been inferior to the properties of geopolymers produced using just fly ash or just brick body.
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Eckl, Ondřej. "Využití některých velkoobjemově produkovaných druhotných surovin k přípravě pojiv a kompozitů na bázi geopolymerů." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2009. http://www.nusl.cz/ntk/nusl-216460.
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Rincón, Acacio. "Development of low cost waste-derived sintered glass-ceramics for energy saving and recovery." Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3426371.
Full textAbstract:
A new technique for the production of cellular glass and glass-ceramics foams is the main goal of the hereby presented research activities. It is based on a combination of alkali-activation of silica-rich materials, with subsequent inorganic gel casting foaming by means of a surfactant and final heat treatment trough sinter-crystallisation process. This new process is less expensive and more environmentally sustainable than the current procedures based on mixtures of glass powders and foaming agents, which decompose and release gases at a temperature significantly above the softening glass point, and is conceived as an alternative route to valorise silica-rich waste materials
The alkali activation of glass waste allows to obtain well-dispersed concentrated suspensions, undergoing gelation by treatment at low temperature (40-80 °C), due to the formation of silicate hydrates. An extensive direct foaming was achieved by mechanical stirring of partially gelified suspensions, also comprising a surfactant. The final microstructure (total amount of porosity, cell size) can be directly correlated with the degree of gelation. A sintering treatment, at only 700 °C, was finally applied to stabilise the structures and limit the leaching of alkaline ions.
The approach proved to be extended to different glasses and industrial waste mixtures leading to different gels after alkali activation. Alkali activation of soda-lime waste glass was exploited through mixing with iron-rich inorganic waste from a copper slag and fly ash from coal combustion. The approach was also extended to different glass-based material coming from waste, such as an alumino-boro-silicate glass from the recycling of pharmaceutical vials, and vitrified bottom ashes from municipal solid waste incinerators. A considerable number of processing parameters combinations (such as surfactants, activating solution, curing times, conditions for heating treatments etc.) were explored and understood.
Apart from waste-derived materials and applications in the building industry, the technique was also applied to create highly porous bioactive glass-ceramics scaffolds; the successful production of highly homogeneous foams proves the versatility in the approach.
The progressive hardening associated with inorganic polymerisation configuring an ‘inorganic gel casting’ has also been used to produce advanced ceramics, such as mullite and cordierite foams and scaffolds. These materials were obtained through the thermal treatment of engineered alkali activated suspensions consisting of a Na-geopolymer enriched with reactive γ-Al2O3 powders in the case of mullite, and reactive γ-Al2O3 and talc in the synthesis of cordierite. The gelation was studied in order to have a proper viscosity for trapping air during vigorous mechanical stirring or maintaining the shape of the scaffold struts obtained by direct ink writing. After the hardened samples were obtained, sodium ions were extracted through ion exchange in ammonium nitrate solution. Finally, the ion-exchanged foams were successfully converted into pure mullite or cordierite foams and scaffolds with the application of a firing treatment.
Alkali activation was the basis for the manufacturing of lightweight granules according to a ‘spheroidisation technique’ consisting in the casting of fine glass powders on a rotary drum, before firing. The hardened suspensions of soda-lime glass obtained from alkaline activation, were reduced into fragments and cast on a rotary drum with dry glass. The firing of green granules was accompanied by a significant foaming, owing to the decomposition of hydrated compounds.L’obiettivo delle attività di ricerca presentate è l’individuazione di una nuova tecnica per la produzione di schiume di vetro e vetroceramiche, basata sulla combinazione di un processo di attivazione alcalina di materiali ricchi di silice e successiva schiumatura del gel inorganico mediante un tensioattivo e un trattamento termico finale mediante sinterizzazione e cristallizzazione (“sinter-crystallisation”). Si tratta di un processo più economico ed ecologicamente sostenibile rispetto alle attuali procedure, basate su miscele di polveri di vetro e agenti schiumogeni, che sono soggette a decomposizione e rilasciano gas a una temperatura significativamente superiore al punto di rammollimento (“softening point”) del vetro. Questa nuova tecnica offre una strategia alternativa per la valorizzazione di materiali di scarto ad alto contenuto di silice. L'attivazione alcalina degli scarti di vetro consente di ottenere sospensioni concentrate ben disperse, le quali subiscono una gelificazione mediante trattamento a bassa temperatura (40-80°C), ascrivibile alla formazione di idrati di silicato. Si è ottenuta una schiumatura diretta ed estesa mediante agitazione meccanica di sospensioni parzialmente gelificate, con l’ausilio di un tensioattivo. La microstruttura finale (livello totale di porosità, dimensione delle celle) può essere direttamente correlata al grado di gelificazione. È stato infine applicato un trattamento di sinterizzazione a soli 700°C, per stabilizzare le strutture e limitare la lisciviazione (“leaching”) di ioni alcalini. È stata dimostrata l’applicabilità di tale approccio a diverse tipologie di vetro e miscele di rifiuti industriali, ottenendo diversi gel in seguito all'attivazione alcalina. L'attivazione alcalina del vetro sodico-calcico di scarto è stata sfruttata attraverso la miscelazione con rifiuti inorganici ricchi di ferro da scorie di rame e ceneri volatili prodotte dalla combustione del carbone. L'approccio è stato esteso anche a diversi materiali a base di vetro provenienti da rifiuti, come il vetro borosilicato proveniente dal riciclaggio di fiale farmaceutiche e ceneri pesanti vetrificate provenienti dagli inceneritori di rifiuti solidi urbani. Sono state esplorate e comprese diverse combinazioni di parametri di processo (tensioattivi, soluzioni di attivazione, tempi di polimerizzazione, condizioni per il trattamento termico ecc.). Oltre che per la creazione di materiali derivati dai rifiuti e l’individuazione di possibili applicazioni nel settore dell'edilizia, la tecnica è stata utilizzata anche per creare scaffold vetroceramici bioattivi altamente porosi, a dimostrazione della versatilità dall'approccio. L'indurimento progressivo associato alla polimerizzazione inorganica che configura un "gel inorganico" è stato inoltre sfruttato per produrre ceramiche avanzate, come schiume e scaffold di mullite e cordierite. Questi materiali sono stati ottenuti mediante il trattamento termico di sospensioni ingegnerizzate attivate alcalinamente, costituite da un geopolimero a base di sodio arricchito con polveri reattive γ-Al2O3, nel caso della mullite, e γ-Al2O3 reattivo e talco, nella sintesi della cordierite. La gelificazione è stata studiata allo scopo di ottenere una viscosità appropriata per intrappolare l'aria in condizioni di vigorosa agitazione meccanica o per mantenere la forma dei filamenti negli scaffold ottenuti mediante stampa diretta. In seguito all’ottenimento dei campioni induriti, sono stati estratti gli ioni di sodio mediante scambio ionico in soluzione di nitrato di ammonio. Infine, le schiume sottoposte a scambio ionico sono state convertite in schiume e scaffold di mullite o cordierite pura con l'applicazione di un trattamento di cottura. L'attivazione alcalina è stata la base di partenza per la produzione di granuli leggeri tramite una "tecnica di sferoidizzazione" che consiste nella aggregazione di polveri di vetro sottili su un tamburo rotante, prima del tratamento termico. Una volta indurite, le sospensioni di vetro sodico-calcico ottenute dall’attivazione alcalina sono state ridotte in frammenti e collocate su un tamburo rotante con polvere di vetro secco. Il tratamento termico dei granuli verdi ha determinato una significativa formazione di schiuma, dovuta alla decomposizione dei composti idrati.
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Chang，Hung-Ming and 張宏銘. "Effect of Alkali Metals on the Activation of GGBFS." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/91421402719845717254.
Full textAbstract:
碩士國立臺灣海洋大學
河海工程學系
105
The study aims to investigate the influence on adding Alkali metal to mortar and its degree of effect on activating Ground Granulated Blast Furnace Slag(GGBFS). Through the control group and adding different portion of GGBFS as well as different portion of Alkali metal experiment data to compare its degree of effect both on its strength and its fluidity, this study tried to figure out the best proportion of replacement of Alkali metal and GGBFS in the mortar. GGBFS added to an alkali metal compressive strength for 28 days, with 120 BF ballast powder (with 60% quantity), which is higher than the average compressive strength of cement mortar strength test, adding 120 BF ballast powder (with 60% quantity) 0.1% alkali metal is the best. Blast furnace ballast powder 100 level (fineness of 4200 cm2/g) and 120 level (fitness of 5200 cm2/g) as well as after activating Alkali metal, in this study, the best result is known to be the 60% quantity of blast furnace ballast powder. When cement mortar is replaced by blast furnace ballast powder, the fluidity of cement mortar will decrease and Alkali metal is able to elevate the fluidity of cement mortar.. Also, the quantity of Alkali metal over 0.2 is considered to increase considerably. Conversely, after the hydration of blast furnace ballast powder and Alkali metal, the fluidity of cement mortar is lower than the general concrete. However, it also revealed that the quantity of Alkali metal has its effect on increasing the fluidity of cement mortar. This study, after the hydration of blast furnace ballast powder and Alkali metal, the result of fluidity is not considered to be satisfactory. As a result, it is recommended to add different kinds of Alkali metal for further research to investigate adding different kinds of Alkali metal and its best fluidity.
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Matos, Fábio André Cancelas. "Improvement of a lime-based mortar's thermal properties using alkaline activation." Master's thesis, 2018. http://hdl.handle.net/10773/25827.
Full textAbstract:
This dissertation was developed as proposed by company Domínio Do Ligante – Argamassas Tradicionais Pré-doseadas Lda. In cooperation with the Department of Geoscience of University of Aveiro, granting the author the conclusion of the second cycle of studies in Geomaterials and Geological Resources by the aforementioned institution.
The main goal of this study is to improve the thermal insulation properties, mainly thermal conductivity, of lime-based mortar ‘DDL.ECM Projeção’ through alkali activation instead of traditional hydration. As a secondary objective, the study intends to evaluate the technical viability of the product of the experiment in respect to its mechanical properties, capillary absorption and response to acid dissolution.
To fulfill these goals, four laboratory trials took place. In each trial, a control group and two test groups were prepared by mixing the mortar with aqueous solutions of sodium hydroxide and potassium hydroxide, respectively, at a concentration of 3 molar, with the control group being hydrated with water only. The mixtures are then cast in molds and left to cure until demolding. After this, the specimens are to be teste according to the parameters of the study.
The four experimental procedure trials were incapable of producing a sufficient number of viable specimens for testing given their fragility and inconsistency. These results rend impossible de measuring of the properties at study in order to resolve the problem question, as such, the main goal of the dissertation is inconclusive.
The secondary goal, however, is achieved, affirming the technical unviability of alkali activation of DDL.ECM Projeção by the methods employed in this procedure. It is concluded that the CaO content in the mortar is inadequate for this type of process when compared to the inferior content of either SiO2 and Al2O3; not allowing the formation of a stable hybrid systemEsta dissertação foi desenvolvida como proposto pela empresa Domínio Do Ligante – Argamassas Tradicionais Pré-doseadas Lda. em cooperação com o Departamento de Geociências da Universidade de Aveiro, concedendo ao autor a conclusão do segundo ciclo de estudos em Geomateriais e Recursos Geológicos pela instituição supracitada. O objetivo principal deste estudo é melhorar as propriedades de isolamento térmico, nomeadamente a condutividade térmica, da argamassa de cal ‘DDL.ECM Projeção’ procedendo à ativação alcalina da mesma ao invés da hidratação tradicional. Como objetivo secundário pretende-se avaliar ainda a viabilidade técnica do produto desta experiência no que diz respeito a propriedades mecânicas, absorção por capilaridade e resposta à dissolução ácida. Para cumprir estes objetivos, quatro ensaios laboratoriais foram levados a cabo. Em cada ensaio, um grupo de controlo e dois grupos de teste foram preparados misturando a argamassa com soluções aquosas de hidróxido de sódio e hidróxido de potássio, respetivamente, a uma concentração de 3 molar, sendo que o grupo de controlo foi apenas hidratado com água. As misturas foram então aplicadas em moldes e deixadas a curar até ao desmolde. Após isto, os espécimes seriam testados de acordo com os parâmetros em causa. Os quatro ensaios do procedimento experimental não foram capazes de produzir um suficiente número de espécimes viáveis para testar dada a fragilidade ou inconsistência dos mesmos. Estes resultados tornam impossível a medição das propriedades em estudo para resolução da questão problema, sendo o objetivo principal da dissertação inconclusivo. Cumpre-se, no entanto, o objetivo secundário afirmando a inviabilidade técnica da ativação alcalina da argamassa DDL.ECM Projeção pelos métodos utilizados neste procedimento. Conclui-se que o conteúdo de CaO da argamassa é inadequado para a realização deste tipo de processo quando comparado com o muito inferior conteúdo quer de SiO2 quer de Al2O3; não permitindo a criação de um sistema híbrido estável
Mestrado em Geomateriais e Recursos Geológicos
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PAN, CHI-ZHEN, and 潘祈臻. "Application of Alkali-activation Foaming Technique on the Fire-proofing Core." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/yrf2d7.
Full textAbstract:
碩士輔英科技大學
環境工程與科學系碩士班
107
China's annual output of inorganic furnaces and inorganic sludge waste is quite large. To reduce the waste of resources caused by misplaced waste and the environmental hazards caused by improper treatment, this study aims to create a future circular economy. The furnace and inorganic sludge are combined by alkali activation technology into a fireproof core material that can compete with commercially available fireproof materials. In this study, coagulation time and foaming control are the main factors to be explored, and the proportioning design is carried out. The basic characteristics of the materials in the experiment are analyzed, and the engineering properties such as density, water absorption, heat transfer coefficient and compressive strength of the finished product are discussed. Microscopic analysis of XDR. The experimental results show that the density of the mixture of A and C is the best fireproof core material under CNS11227-1, and the density of 1.2 and 1.0 of the ratio A and ratio C of CNS12514-8 is the preferred partition wall material. The ratio of heat transfer coefficient of A is 0.39W/mK, the ratio of C is 0.67 W/mK, and the back temperature of 5 kinds of flames is lower than 100 °C for 1 hour at 800 °C. Under the general light compartment fireproof material, the fireproof material of this research is far better than the commercially available material. And the quantitative production of fireproof materials in this study can also achieve bond stability.
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CHIANG, CHIH-CHAO, and 姜智釗. "Effects on Properties of Alkali-activation Binder Materials by Addition of Gypsum Products." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/q84468.
Full textAbstract:
碩士國立臺北科技大學
資源工程研究所
107
In this study, Using ground granulated blast furnace slag (GGBFs) combined with calcium hydroxide and gypsum products to prepar a new type of alkali-activated binder. The reaction of aluminum ions with sulfate ions in the presence of calcium ions in aqueous solution to form ettringite supplemented by pozzolanic reaction leading to the formation of calcium silicate and calcium aluminosilicate hydrates. In the experiment, the physical properties, volume stability and microscopic characteristics of the binder were investigated with different gypsum product fineness, water-to-binder ratio, gypsum product type, gypsum product addition ratio and GGBFs percentage. When the water-to-binder ratio is 0.4, the ratio of calcium hydroxide to gypsum product is 4, the compressive strength of the binder can reach 44 MPa at 28 days. The compressive strength and setting time were compliance with the specifications of blast-furnace cement in Taiwan and Japan. Thermogravimetric mass loss showed that the hydrated product increased in the temperature range of 40~200℃ with the age, indicating that the amount of hydrated product increased as the increase of age. When the ratio of calcium hydroxide to gypsum product was changed to 0.43, result in gypsum product was added, and more ettringite was formed, but the results showed of XRD and SEM analysis still lot of gypsum were remained that make the strength of the binder was reduced. XRD analysis of different gypsum product binder for 28 days showed that the building gypsum has more significant reactivity than the other in the alkali-activated binder material. Despite the expansion and shrinkage rate of the binder was prepared by building gypsum is stable at normal temperature, but the appearance of the sample after drying at a temperature of 105℃ has more cracks obviously as the amount of building gypsum increases. The dry shrinkage indicates that the gypsum product still needs to consider the volume stability caused by the drying of the sample when added to the alkali-activated binder material. However, the binder after high temperature and high pressure curing in Autoclave still maintains a complete type, and the autoclave test expansion and shrinkage rate were compliance with the specifications of blast-furnace cement in Taiwan and Japan.
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Zheng, Yong Chu. "Shrinkage behaviour of geopolymer." 2009. http://repository.unimelb.edu.au/10187/7157.
Full textAbstract:
Geopolymer cements offer an alternative to, and potential replacement for, ordinary Portland cement (OPC). Geopolymer technology also has the potential to reduce global greenhouse emissions caused by OPC production. There is already a considerable amount of work and research conducted on geopolymers in the past decades, and it is now possible to implement this technology commercially. However, to ensure that geopolymer becomes commercially available and able to be used in the world, further understanding of its ability to provide durable and long lasting materials is required. One main property which is still relatively unexplored compared to other properties is its shrinkage properties. The objective of this thesis is therefore to examine the shrinkage of geopolymers and factors which might influence it.The factors which influence geopolymer strength were investigated as being the factors which may influence shrinkage. The selection of the activating solution is an important factor in forming the final product of a geopolymer. Activating solution SiO2/Na2O ratio is determined to be an important influence on the shrinkage of geopolymer. SEM images of the samples enable observation of the sample topology and microstructure. An important observation was the existence of a ‘knee point’ which also occurs in OPC shrinkage. The ‘knee point’ is the point where the shrinkage goes from rapid shrinkage to slow shrinkage. From SEMs it is noted that the samples past the knee point are shown to have a smoother topology which means it is more reacted.
Autogenous shrinkage is an important issue for OPC containing a high amount of silica, and is also a key factor in geopolymer shrinkage. Autogenous shrinkage is tested by keeping samples in a sealed environment where water lost to drying is kept to a minimum. It is noted that sealing and bagging the samples reduces the shrinkage considerably. The water to cement ratio, which is an important factor in OPC shrinkage, is also explored for the case of geopolymers. Water content plays an important role in determining early stage shrinkage, and has little to no effect on the later stage shrinkage. The water loss from the samples during drying on exposure to environment is noted and compared. The addition of more water did not necessary means that more water was lost.
Addition of slag is known to be beneficial to geopolymers by giving early structural strength and faster setting time. Commercial geopolymer concrete will also include the use of slag. However, the addition of slag up to a certain extent gives a deleterious affect on shrinkage.
A different type of Class F fly ash source with different composition data was used to see its effect on shrinkage, with only a slight influence observed between the two ashes tested. Fly ash was also ground for different lengths of time before use in geopolymerization, with grinding for less than 12 hours giving higher shrinkage than an unground sample, but shrinkage the decreasing with grinding for 18 or 24 hours. This initial higher shrinkage has been attributed to the mechanism of grinding which resulted in unevenly shaped fly ash particles taking up a larger initial volume resulting in higher shrinkage. The sample grinded for 24 hours showed higher shrinkage due to the particle size to be so fine that agglomerates may have form during mixing which would result in a lower reaction rate which increases the shrinkage. Elevated curing temperatures also reduce geopolymer shrinkage.
Thus, it is clear that the shrinkage of geopolymers is influenced by a wide range of variables, and more notably by a few important variables: activating solution ratio, addition of water, grinding and bagging. The shrinkage of geopolymers can be correlated to the strength to a certain extent. However, the understanding of the shrinkage of geopolymers is still at a very initial phase, and further research is required.
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Chia, Chia-Jung, and 賈佳蓉. "A Study on Application of Alkali-activation and CO2 Mineralization for Integrated Utilization of Electric Arc Furnace Slags." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/7bjpcn.
Full textAbstract:
碩士國立臺北科技大學
資源工程研究所
107
The aim of this study was to evaluate the feasibility of EAF reduction slag powder, calcium hydroxide, and ground granulated blast furnace slag used as binder materials and used to produce mortar and block with EAF oxidation slag and effectiveness of different curing methods on the volume stability of mortar and block. Firstly, the basic physicochemical properties of ground granulated blast furnace slag and EAF slag powder are analyzed. The EAF reduction slag powder is used to excitation alkaline activator combined with ground granulated blast furnace slag, and then the binder material is combined with EAF oxidation slag to produce mortar and block that the effect of mortar on the properties was discussed by saturated lime water curing and CO2 mineralization curing. This study was used in the fineness of EAF reduction slag about 7160 cm2/g to be used as a binder, and used to produce mortar with EAF oxidation slag, the 28-day compressive strength of the mortar is 29.96 MPa. The result of ASTM C1260 test shows the mortar bar has the potentially expansibility of volume and the expansion rate is 0.059%, and was found the surface of the mortar bar has white powders. The white powders are sampled and analyzed by XRD. The main components of white powders are Mg(OH)2, respectively. Furthermore, this study was used the CO2 mineralization technology to improve the volume stability of mortar and block. The mortar was cured by saturated lime water for 7 days, and then cured by 25% CO2 gas/liquid-phase CO2 mineralization, the gas-phase CO2 mineralization curing mortar compressive strength is able to achieve 26 MPa about 14th day, after then the compressive strength hasn’t increased. Another, the compressive strength of CO2 mineralization mortar is unpredictable, due to the precipitation of calcium ions in the mortar to the surface and react with carbonate ions to form carbonate precipitates. The results of thermos-gravimetric analysis showed that the thermal weight loss of the mortar increased from 0.45% to 1.55% as the curing time of gas-phase CO2 mineralization increased to 42 days, indicating that the gas-phase CO2 mineralization mortar is the best method. The result of volume stability shows that the mortar was cured by the 25% CO2 gas-phase CO2 mineralization, and the volume expansion was tested by ASTM C1260 for 16 days. The mortar was cured for 0 days to 42 days that the surface pop-outs decreased from 20 points to 2 points, and the volume expansion was also reduced from 5.01% to 2.016%. The block was cured by saturated lime water for 7 days, and then cured by 25% CO2 gas-phase CO2 mineralization for 28 days, the compressive strength is able to achieve 35.57 MPa, after then the compressive strength hasn’t increased. The result of volume stability shows that the pop-outs were greatly reduced, and the volume expansion was also reduced with the increase of gas-phase CO2 mineralization curing time. The block was cured by 7 days of saturated lime water and then cured by 25% CO2 gas-phase CO2 mineralization for 28 days, which has better volume stability.
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"Alkali Activated Systems: Understanding the Influence of Curing Conditions and Activator Type/Chemistry on the Mechanical Strength and Chemical Structure of Fly Ash/Slag Systems." Master's thesis, 2013. http://hdl.handle.net/2286/R.I.18755.
Full textAbstract:
abstract: The alkali activation of aluminosilicate materials as binder systems derived from industrial byproducts have been extensively studied due to the advantages they offer in terms enhanced material properties, while increasing sustainability by the reuse of industrial waste and byproducts and reducing the adverse impacts of OPC production. Fly ash and ground granulated blast furnace slag are commonly used for their content of soluble silica and aluminate species that can undergo dissolution, polymerization with the alkali, condensation on particle surfaces and solidification. The following topics are the focus of this thesis: (i) the use of microwave assisted thermal processing, in addition to heat-curing as a means of alkali activation and (ii) the relative effects of alkali cations (K or Na) in the activator (powder activators) on the mechanical properties and chemical structure of these systems. Unsuitable curing conditions instigate carbonation, which in turn lowers the pH of the system causing significant reductions in the rate of fly ash activation and mechanical strength development. This study explores the effects of sealing the samples during the curing process, which effectively traps the free water in the system, and allows for increased aluminosilicate activation. The use of microwave-curing in lieu of thermal-curing is also studied in order to reduce energy consumption and for its ability to provide fast volumetric heating. Potassium-based powder activators dry blended into the slag binder system is shown to be effective in obtaining very high compressive strengths under moist curing conditions (greater than 70 MPa), whereas sodium-based powder activation is much weaker (around 25 MPa). Compressive strength decreases when fly ash is introduced into the system. Isothermal calorimetry is used to evaluate the early hydration process, and to understand the reaction kinetics of the alkali powder activated systems. A qualitative evidence of the alkali-hydroxide concentration of the paste pore solution through the use of electrical conductivity measurements is also presented, with the results indicating the ion concentration of alkali is more prevalent in the pore solution of potassium-based systems. The use of advanced spectroscopic and thermal analysis techniques to distinguish the influence of studied parameters is also discussed.Dissertation/Thesis
M.S. Engineering 2013
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"Novel Materials and Processing Routes Using Alkali-activated Systems." Doctoral diss., 2019. http://hdl.handle.net/2286/R.I.54957.
Full textAbstract:
abstract: This dissertation aims at developing novel materials and processing routes using alkali activated aluminosilicate binders for porous (lightweight) geopolymer matrices and 3D-printing concrete applications. The major research objectives are executed in different stages. Stage 1 includes developing synthesis routes, microstructural characterization, and performance characterization of a family of economical, multifunctional porous ceramics developed through geopolymerization of an abundant volcanic tuff (aluminosilicate mineral) as the primary source material. Metakaolin, silica fume, alumina powder, and pure silicon powder are also used as additional ingredients when necessary and activated by potassium-based alkaline agents. In Stage 2, a processing route was developed to synthesize lightweight geopolymer matrices from fly ash through carbonate-based activation. Sodium carbonate (Na2CO3) was used in this study to produce controlled pores through the release of CO2 during the low-temperature decomposition of Na2CO3. Stage 3 focuses on 3D printing of binders using geopolymeric binders along with several OPC-based 3D printable binders. In Stage 4, synthesis and characterization of 3D-printable foamed fly ash-based geopolymer matrices for thermal insulation is the focus. A surfactant-based foaming process, multi-step mixing that ensures foam jamming transition and thus a dry foam, and microstructural packing to ensure adequate skeletal density are implemented to develop foamed suspensions amenable to 3D-printing. The last stage of this research develops 3D-printable alkali-activated ground granulated blast furnace slag mixture. Slag is used as the source of aluminosilicate and shows excellent mechanical properties when activated by highly alkaline activator (NaOH + sodium silicate solution). However, alkali activated slag sets and hardens rapidly which is undesirable for 3D printing. Thus, a novel mixing procedure is developed to significantly extend the setting time of slag activated with an alkaline activator to suit 3D printing applications without the use of any retarding admixtures. This dissertation, thus advances the field of sustainable and 3D-printable matrices and opens up a new avenue for faster and economical construction using specialized materials.Dissertation/Thesis
Doctoral Dissertation Civil, Environmental and Sustainable Engineering 2019
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"Kinetics of Alkaline Activation of Slag and Fly ash-Slag Systems." Master's thesis, 2012. http://hdl.handle.net/2286/R.I.15972.
Full textAbstract:
abstract: Alkali-activated aluminosilicates, commonly known as "geopolymers", are being increasingly studied as a potential replacement for Portland cement. These binders use an alkaline activator, typically alkali silicates, alkali hydroxides or a combination of both along with a silica-and-alumina rich material, such as fly ash or slag, to form a final product with properties comparable to or better than those of ordinary Portland cement. The kinetics of alkali activation is highly dependent on the chemical composition of the binder material and the activator concentration. The influence of binder composition (slag, fly ash or both), different levels of alkalinity, expressed using the ratios of Na2O-to-binders (n) and activator SiO2-to-Na2O ratios (Ms), on the early age behavior in sodium silicate solution (waterglass) activated fly ash-slag blended systems is discussed in this thesis. Optimal binder composition and the n values are selected based on the setting times. Higher activator alkalinity (n value) is required when the amount of slag in the fly ash-slag blended mixtures is reduced. Isothermal calorimetry is performed to evaluate the early age hydration process and to understand the reaction kinetics of the alkali activated systems. The differences in the calorimetric signatures between waterglass activated slag and fly ash-slag blends facilitate an understanding of the impact of the binder composition on the reaction rates. Kinetic modeling is used to quantify the differences in reaction kinetics using the Exponential as well as the Knudsen method. The influence of temperature on the reaction kinetics of activated slag and fly ash-slag blends based on the hydration parameters are discussed. Very high compressive strengths can be obtained both at early ages as well as later ages (more than 70 MPa) with waterglass activated slag mortars. Compressive strength decreases with the increase in the fly ash content. A qualitative evidence of leaching is presented through the electrical conductivity changes in the saturating solution. The impact of leaching and the strength loss is found to be generally higher for the mixtures made using a higher activator Ms and a higher n value. Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR) is used to obtain information about the reaction products.Dissertation/Thesis
M.S. Civil Engineering 2012
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Dias, Nuno Amadeu Antunes. "Geopolímeros: contributos para a redução das eflorescências." Master's thesis, 2012. http://hdl.handle.net/1822/30326.
Full textAbstract:
Dissertação de mestrado integrado em Engenharia CivilO cimento Portland constitui, desde há várias décadas, um dos principais materiais utilizados em estruturas de betão (sector da construção). Embora produzindo resultados interessantes, nomeadamente ao nível da resistência mecânica, possui grandes desvantagens a nível ambiental. A principal desvantagem é a libertação de dióxido de carbono por via da calcinação dos materiais calcários utilizados no seu fabrico. Tal deve-se aos custos associados à extração da matéria-prima necessária mas também ao grande consumo energético que se verifica no seu fabrico. Tornou-se portanto imperioso arranjar materiais alternativos a este tipo de material. Surgem então os ligantes geopoliméricos, também designados por ligantes obtidos por ativação alcalina, que constituem a solução da comunidade científica na busca por materiais ligantes alternativos ao cimento Portland, os quais sejam mais duráveis e que possuam um melhor desempenho ambiental. No entanto, estes ligantes não estão totalmente isentos de desvantagens, estando por vezes associados à formação de eflorescências. Com o objetivo de reduzir ou até mesmo extinguir eflorescências nos geopolímeros, procedeu-se à cura das diversas argamassas a várias temperaturas durante 24 horas após a desmoldagem e, por outro lado, aumentou-se a percentagem de alumina na argamassa através da adição de cimento aluminoso. Os resultados mostram que o uso de cura com elevação de temperatura reduz as eflorescências. Além disso aumenta a resistência à compressão. Tendo-se registado o valor da resistência mais elevado para uma temperatura de 60ºC durante 24 horas. E, ao contrário do que se esperava, a adição de teores de cimento aluminoso não contribuem para a redução de eflorescências, mas sim o contrário.
In the last decades Portland cement was and still is the most used binder for the execution of concrete structures. Being associated with a high mechanical resistance it is however responsible for a significant environmental impact which includes extraction of nonrenewable resources and high energy consumption. Its main environmental disadvantage relates to the emission of carbon dioxide when limestone is subject to calcination. Therefore, investigation on alternative greener binders is needed. Geopolymers also known as alkali-activated binders represent alternative binders for Portland cement replacement having a high durability and a low environmental impact. However, they are not without some drawbacks one being efflorescences. The present Dissertation try to investigate two different ways to reduce efflorescences in geopolymeric binders based on fly ash. For one hand the use of thermal treatment and for another the use of a mixture of fly ash and cement with high aluminum content. The results show that the use of a thermal treatment can reduce the efflorescences. The thermal treatment also increases the compressive strength. The best mechanical results occurred at a curing temperature of 60 ºC during 24h. However, the geopolymers based on a mixture of fly ash and cement with high aluminum content didn´t show a reduction on efflorescences.