Dissertations / Theses on the topic 'Geopolymer mortars'

Orientador: José Luiz Pinheiro Melges
Resumo: 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)
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In the process of water treatment for public supply, which is made in the water treatment plants (WTPs), a waste conventionally called sludge is formed. As in the soil, the main components of WTP sludge are silicon (Si), aluminum (Al) and iron (Fe). This composition allowed to suggest that this waste could be used in the production of inorganic polymers - the geopolymers. While conventional polymers are formed by carbon structures, geopolymers are composed of Si and Al structures. They are obtained by dissolving aluminosilicates materials in highly alkaline solution. Among the possible applications, they can be used as pastes, mortars and concretes, in replacement of Portland cement, which is the most used binder in civil construction worldwide. To verify the suitability of the sludge as a geopolymer precursor, this waste was properly benefited by means of mechanical grinding and calcination at 750 °C for 6 hours, being characterized before and after its processing. The results of chemical and mineralogical analyzes proved the adequacy of calcined WTP sludge as a geopolymeric raw material. To check the influence of the sources of raw water abstraction intake on the WTP sludge characteristics and consequently in the properties of materials produced from sludge-based, samples of this waste were collected under the influence of two different water sources. With these samples it produced of two geopolymeric mortars. The final products were properly characterized and the results proved that regardless of the peculiarities of water sources, WTP sludge can be used as a geopolymeric raw material. In the thermal tests the two mortars produced showed indications of refractory bahavior and have been free of calcium hydroxide, therefore, it can be inferred that they are free matrices of deleterious actions of this compound. In the mechanical tests, at 28 days of cure, they reached mechanical strengths of 57 and 79 MPa, on average. Some results evidenced the need for improvements in the formulation of mortars, but in general, it was verified that the use of WTP sludge as a geopolymer precursor material is a very promising alternative for the destination of this waste, making it valuable and useful product for society.
No processo de tratamento de água para abastecimento público, realizado em estações de tratamento de água – ETAs, gera-se um resíduo convencionalmente chamado de lodo. Da mesma forma que acontece no solo, os principais constituintes do lodo de ETA são o silício (Si), o alumínio (Al) e o ferro (Fe). Tal composição permitiu sugerir que este resíduo poderia ser usado na produção de polímeros inorgânicos – os geopolímeros. Enquanto os polímeros convencionais são formados por estruturas de carbono, geopolímeros são constituídos de estruturas de Si e Al. São obtidos através da dissolução de materiais aluminossilicatos em solução altamente alcalina. Dentre as possíveis aplicações, podem ser empregados como pastas, argamassas e concretos, em substituição ao cimento Portland, o material ligante mais utilizado mundialmente na construção civil. Para verificar a adequação do lodo de ETA como material precursor geopolimérico, este resíduo foi devidamente beneficiado por meio de moagem mecânica e calcinação a 750 ° C por 6 horas, sendo caracterizado antes e após seu beneficiamento. Os resultados de análises químicas e mineralógicas comprovarem a adequação do lodo de ETA calcinado como matéria-prima geopolimérica. A fim de avaliar a influência dos mananciais de captação de água bruta nas características do lodo de ETA e, consequentemente, nas propriedades de materiais produzidos à base deste resíduo, foram coletadas amostras de lodo sob influência de dois diferentes mananciais. Com estas amostras produziu-se duas argamassas geopoliméricas. Os produtos finais foram devidamente caracterizados e os resultados comprovaram que, independentemente das peculiaridades dos mananciais, o lodo de ETA pode ser utilizado como material precursor geopolimérico. Nos ensaios térmicos, as duas argamassas produzidas exibiram indícios de comportamento refratário e se mostraram isentas de hidróxido de cálcio, portanto, pode-se inferir que são matrizes livres das ações deletérias ocasionadas por este composto. Nos ensaios de resistência mecânica, aos 28 dias de cura, atingiram 57 e 79 MPa, em média. Alguns resultados evidenciaram a necessidade de melhorias na formulação das argamassas, mas de uma forma geral, constatou-se que o aproveitamento do lodo de ETA como matéria-prima geopolimérica é uma alternativa bastante promissora para a destinação deste resíduo, podendo torná-lo um produto com valor agregado e útil para a sociedade.

This research studies the green geopolymer incorporated with phase change material (PCM) for energy saving in buildings. First class F fly ash (FA) based-geopolymer binder was studied. In order to improve the mechanical properties, low calcium slag (SG) was added to the FA to produce geopolymer. The effect of different factors including SG content (at different relative amounts FA/SG = 0/100, 25/75, 50/50, 75/25 and 100/0), NaOH solution at different concentrations (7.5, 10 and 15 M), various curing times (1, 2, 4, 7, 14 and 28 days) and curing temperatures (25 (ambient), 45, 60, 75 and 90°C) was investigated. The unit weight and uniaxial compressive strength (UCS) of the geopolymer specimens were measured. Scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX) and X-ray diffraction (XRD) were also performed to characterize the microstructure and phase composition of the geopolymer specimens. The results show that the incorporation of SG not only improves the strength of the geopolymer specimens but also decreases the initial water content and thus the NaOH consumption at the same NaOH concentration required for geopolymer production. In addition, the inclusion of SG increases the unit weight of the geopolymer specimens, simply because SG has a much greater specific gravity than FA. The results also show that the strength of the FA/SG-based geopolymer develops rapidly within only 2 days and no obvious gain of the strength after 7 days. The optimum curing temperature (the curing temperature at which the maximum UCS is obtained) at a FA/SG ratio of 50/50 is around 75°C. Second, FA-based geopolymer concrete was synthesized and the effect of different factors including sodium silicate to sodium hydroxide (SS/SH) ratio, aggregate shape, water to fly ash (W/FA) ratio, curing time, water exposure and PCM inclusion on the compressive strength of the geopolymer concrete specimens cured at different ambient temperatures was studied. The results show that the UCS of the specimens increases with higher SS/SH and W/FA ratios up to a certain level and then starts to decrease at higher ratios. The results also indicate that a major portion of the strength of the specimens cured at ambient temperatures develops within the first four weeks. In addition the strength of the FA-based geopolymer concrete is slightly decreased with water exposure and PCM incorporation. Third, the mechanical and thermal properties of geopolymer mortar synthesized with FA and different amount of PCM were studied and the effect of incorporated PCM on the unit weight and UCS of geopolymer mortar was evaluated. SEM imaging was performed to identify the change of micro structure of the geopolymer mortar after incorporation of PCM. The thermal properties of the geopolymer mortar containing different amount of PCM were also characterized using differential scanning calorimetry (DSC) analysis. In addition model tests were performed using small cubicles built with geopolymer mortar slabs containing different amount of PCM to evaluate the effectiveness of geopolymer mortar wall with incorporated PCM in controlling the heat flow and internal temperature. The results indicate that both the unit weight and UCS of the geopolymer mortar decrease slightly after PCM is incorporated, mainly due to the small unit weight and low strength and stiffness of the PCM, respectively. However, the compressive strength of geopolymer mortar containing up to 20% PCM is still sufficiently high for applications in buildings. The results also show that the incorporation of PCM leads to substantial increase of heat capacity and decrease of thermal conductivity of the geopolymer mortar and is very effective in decreasing the temperature inside the cubicles. Finally, a numerical study on the thermal performance of geopolymer with incorporated PCM was carried out. In order to simulate the heat transfer through geopolymer containing PCM, a simplified method was first presented. The influence of phase transition was linked to the energy balance equation through variable specific heat capacity of the PCM-geopolymer. The thermal properties of the geopolymer containing PCM for the numerical analysis were determined using DSC and guarded heat flow (GHF) tests. The simplified method was validated based on the good agreement between the numerical and experimental results. With the validated model, the effect of various factors including the specific heat capacity, thermal conductivity and wall thickness on the thermal performance of PCM-geopolymer walls was studied. Then a modified numerical method was proposed for simulating the whole thermal transfer processes and the simulation results were used to conduct the economic evaluation of PCM-geopolymer walls for energy savings in buildings.

Current geopolymer formulation prescribes mixture proportions through bulk methods, considering both the inert and reactive composition of the mixture constituents. This is believe to be attributed to inconstancies in strength outcomes and production processes. This research aimed to further develop the amorphous approach to geopolymer formulation, where by geopolymer mixture proportions are prescribed with reference to the reactive composition of the feeder stocks. This research focused on binary, ternary and blended geopolymer binders within mortars.

This paper reports the development of an Alkali Activated Binder (AAB) with an emphasis on the performance and the durability of the AAB-matrix. For the development of the matrix, the reactive components granulated slag and coal fly ash were used, which were alkali activated with a mixture of sodium hydroxide (2 - 10 mol/l) and aqueous sodium silicate solution (SiO2/Na2O molar ratio: 2.1) at ambient temperature. A sodium hydroxide concentration of 5.5 mol/l revealed the best compromise between setting time and mechanical strengths of the AAB. With this sodium hydroxide concentration, the compressive and the 3-point bending tensile strength of the hardened AAB were 53.4 and 5.5 MPa respectively after 14 days. As a result of the investigation of the acid resistance, the AAB-matrix showed a very high acid resistance in comparison to ordinary Portland cement concrete. In addition, the AAB had a high frost resistance, which had been validated by the capillary suction, internal damage and freeze thaw test with a relative dynamic E-Modulus of 93% and a total amount of scaled material of 30 g/m2 after 28 freeze-thaw cycles (exposure class: XF3).

[ES] El descubrimiento del cemento Portland ha cambiado nuestra forma de construir, pero también es el responsable de grandes emisiones de CO2 a la atmósfera durante su fabricación (~1450 ᴼC), agravando la crisis actual que está sufriendo nuestro planeta debido al cambio climático y sus consecuencias en todo el medio ambiente. Por lo tanto, una alternativa más sostenible en la construcción es la utilización de la cal que necesita menor temperatura para su fabricación (~900 ᴼC). Si bien la introducción de puzolanas naturales o artificiales en morteros de cal han mejorado sus propiedades mecánicas y de durabilidad, estas aún tienen el inconveniente de ganar resistencias a edades largas de curado. Es por esta razón que en la presente tesis se pretende eliminar este inconveniente técnico, buscando la asociación de la cal con nuevos conglomerantes más sostenibles a partir de residuos para obtener morteros mixtos denominados cal/puzolana-geopolímero. Los residuos estudiados fueron: el catalizador gastado de craqueo catalítico, la ceniza de cascara de arroz, la tierra diatomea de origen residual y la ceniza de lodo de depuradora. También se estudia una puzolana natural proveniente de la República de Guatemala. En los morteros cal/puzolana (cal/FCC, cal/CCA, cal/CLD) se ha realizado sustituciones en peso hasta un 50 % de la mezcla cal/puzolana por geopolímero. El geopolímero se obtiene por una combinación del FCC como precursor y diferentes activadores alcalinos siendo estos la mezcla de: NaOH/Na2SiO3, NaOH/CCA, NaOH/TDN y NaOH/TDR. Los últimos tres sustituyen al silicato comercial como fuente de sílice alternativa. Asimismo, se realizaron estudios a nivel mecánico y microestructural. Para los estudios microestructurales, tanto de muestras endurecidas como de materiales de partida, se emplearon como técnicas: FRX, ADL, TG, DRX y FESEM. Los resultados han demostrado con éxito que añadir pequeñas cantidades de geopolímero sobre el sistema cal/puzolana fue notable, debido a que este potenció la formación de los nuevos productos de reacción, lo que mejoró la resistencia mecánica de los morteros desde las primeras horas de curado, llegando a obtener 7 veces más de resistencia que un mortero control cal/puzolana en 1 día de curado. El reemplazo del silicato de sodio comercial por CCA, TDN, TDR, como fuente de sílice, condujo a mejores desempeños del mortero en términos de resistencia a la compresión. Además, redujo el coeficiente de absorción de agua por capilaridad y aumento el tiempo de exposición a los ciclos hielo-deshielo frente a los morteros activados con activadores comerciales. Finalmente, los conglomerantes desarrollados en este estudio podría beneficiar tanto a la gestión de residuos como al desarrollo de materiales de construcción más sostenibles, aportando a los objetivos propuestos en la agenda 2030.
[CA] El descobriment del ciment Portland ha canviat la nostra manera de construir, però també és el responsable de grans emissions de CO¿ a l'atmosfera durant la seva fabricació (~1450 ᴼC), agreujant la crisi actual que està patint el nostre planeta degut al canvi climàtic i les seves conseqüències en tot el medi ambient. Per tant, una alternativa més sostenible en la construcció és la utilització de la calç que necessita menor temperatura per a la seva fabricació (~900 ᴼC). Si bé la introducció de putzolanes naturals o artificials en morters de calç han millorat les seves propietats mecàniques i de durabilitat, aquestes encara tenen l'inconvenient de guanyar resistències a edats llargues de curat. És per aquesta raó que en la present tesi es pretén eliminar aquest inconvenient tècnic, buscant l'associació de la calç amb nous conglomerants més sostenibles a partir de residus per a obtenir morters mixtos denominats calç/putzolana-geopolímer. Els residus estudiats van ser: el catalitzador gastat del craqueig catalític, la cendra de closca d'arròs, la terra diatomea d'origen residual i la cendra de llot de depuradora. També es va estudiar una putzolana natural provinent de la República de Guatemala. En els morters calç/putzolana (calç/FCC, calç/CCA, calç/CLD) s'ha realitzat substitucions en pes fins a un 50 % de la barreja calç/putzolana per geopolímer. El geopolímer s'obté per una combinació del FCC com a precursor i diferents activadors alcalins, sent aquests la mescla de: NaOH/Na2SiO3, NaOH/CCA, NaOH/TDN i NaOH/TDR. Els últims tres substitueixen al silicat comercial com a font de sílice alternativa. Així mateix, es van realitzar estudis a nivell mecànic i microestructural. Per als estudis microestructurals, tant de mostres endurides com de materia primera, es van emprar tècniques com: FRX, ADL, TG, DRX i FESEM. Els resultats han demostrat amb èxit que afegir petites quantitats de geopolímer sobre el sistema calç/putzolana va ser notable, pel fet que aquest va potenciar la formació dels nous productes de reacció, la qual cosa va millorar la resistència mecànica dels morters des de les primeres hores de curat, arribant a obtenir 7 vegades més de resistència que un morter control calç/putzolana en 1 dia de curat. El reemplaçament del silicat de sodi comercial per CCA, TDN, TDR, com a font de sílice, va conduir a millors acompliments del morter en termes de resistència a la compressió. A més, va reduir el coeficient d'absorció d'aigua per capil·laritat i va augmentar el temps d'exposició als cicles gel-desgel enfront dels morters activats amb activadors comercials. Finalment, els conglomerants desenvolupats en aquest estudi podrien beneficiar tant a la gestió de residus com al desenvolupament de materials de construcció més sostenibles, aportant als objectius proposats en l'Agenda 2030.
[EN] The discovery of Portland cement has changed the way we build; however, it is also responsible for large CO2 emissions into the atmosphere during its manufacturing (~ 1450 ᴼC), thereby aggravating the current crisis that our planet is suffering due to climate change and its consequences in the environment. Thus, a more sustainable alternative in construction is the use of lime that requires a lower temperature for its manufacturing (~ 900 ᴼC). The introduction of natural or artificial pozzolans in lime mortars has improved their mechanical properties and durability. Nevertheless, they present some technical disadvantages, as the low compressive strength, especially at early curing time. This thesis aims to eliminate this technical disadvantage by mixing lime with new more sustainable binders derived from waste, obtaining mixed mortars called lime/pozzolan-geopolymer The waste materials studied included fluid catalytic cracking residue (FCC), rice husk ash (CCA), residual diatomite (TDR) and sewage sludge ash (CLD). A natural pozzolan from the Republic of Guatemala was also studied. In the experimental procedure, in lime/pozzolan mortar mixtures (lime/FCC, lime/CCA, lime/CLD), up to 50% of their weight was substituted by geopolymer. The geopolymer is obtained by combining FCC as a precursor, and different alkaline activator mixtures including NaOH/Na2SiO3 (commercial waterglass), NaOH/CCA, NaOH/TDN, and NaOH/TDR, with the last three being an alternative silica source to commercial waterglass. In the same way, both mechanical and microstructural studies were carried out. The following techniques were used: XRF, ADL, TG, XRD and FESEM to assess the microstructural properties of both the raw materials and the hardened samples. The results have demonstrated that adding small amounts of geopolymer to the lime/pozzolan system was remarkable; it enhanced the formation of new reaction products, which improved the mechanical strength of the mortar from the first hours of curing, obtaining 7 times more strength than the lime/pozzolan control mortar in 1 day of curing. The replacement of commercial waterglass by CCA, TDN, TDR, as a source of silica, led to better performance of the mortar in terms of compressive strength. In addition, the coefficient of water absorption by capillarity was reduced and the exposure time during freezing-thawing cycles was increased compared to mortars activated with commercial activators. Finally, the binders developed in this study could benefit both waste management and the development of more sustainable construction materials, contributing to the objectives proposed in the 2030 Agenda.
Gracias al programa ADSIDEO-COOPERACIÓN de la Universitat Politècnica de València, que me ha brindado financiación para la presente investigación.
Villca Pozo, AR. (2021). Utilización de geopolímero para la mejora de las propiedades en morteros cal-puzolana y su empleo en países en desarrollo [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/172663
TESIS

Com o intuito de valorizar resíduos localmente disponíveis foi selecionada como principal matéria prima desta pesquisa, uma cinza de fundo proveniente da queima de carvão mineral para geração de energia em uma usina termoelétrica do Estado. Uma vez que este resíduo ainda não possui destinação que lhe agregue valor, o mesmo é amplamente utilizado no preenchimento de cavas de extração de carvão ou então permanece em bacias de sedimentação, criando assim um panorama suscetível a problemas ambientais além de gerar elevados custos para seu transporte. Neste âmbito surgem com grande destaque o desenvolvimento de ligantes álcali-ativados, dentre estes os geopolímeros, que por utilizarem diversos materiais provenientes de resíduos industriais na sua produção apresentam grande redução na emissão de CO2 e no consumo energético quando são comparados ao cimento Portland. Estes materiais consistem na ativação alcalina de aluminossilicatos amorfos (precursor), sendo estes na maioria das vezes resíduos ou subprodutos industriais. Sendo assim, o presente trabalho teve por objetivo otimizar traços, com base em cinza de fundo, para a produção de ligantes e argamassas geopoliméricas. O método experimental proposto se encontra dividido em diferentes fases subsequentes à seleção e caracterização das matérias primas: (1) síntese de sistemas geopoliméricos em pasta, (2) otimização dos geopolímeros em pasta e (3) produção de argamassas geopoliméricas com verificação das propriedades mecânicas e de absorção de água. A partir da análise dos resultados observou-se que o teor de Na2O = 15% com uma concentração de silicatos solúveis no ativador (expresso como a relação molar SiO2/Na2O) igual a 1 (sistema CF-15-1,0), se mostrou ideal para as misturas com cinza de fundo. A adição de silicatos solúveis propiciou um incremento de resistência aos sistemas produzidos no geral, atingindo em alguns casos o acréscimo de até 40% na resistência aos 28 dias. Quando avaliados diferentes tamanhos de partículas a partir do beneficiamento mecânico das cinzas, observou-se que um diâmetro médio de 7 μm é o mais adequado. Com relação aos sistemas binários e híbridos testados quando comparados aos seus referenciais moldados apenas com cinza de fundo, nenhuma combinação foi capaz de superar as resistências dos referenciais. Quando produzidas argamassas geopoliméricas a partir das combinações com outros resíduos (lodo de anodização do alumínio e catalizador de equilíbrio - resíduo proveniente do processo de craqueamento catalítico em leito fluidizado de frações pesadas do petróleo) e cimento Portland, houveram quedas na resistência à compressão de maneira generalizada. A argamassa utilizada como referência (CF-15-1,0) se mostrou a matriz mais densa e consequentemente atingiu o maior desempenho mecânico com menor absorção de água por capilaridade.
In order to valorise locally available residues, bottom ash (BA) from a thermo-electrical plant was selected as the main material within the project presented here. BA does not have any commercial value and normally it is used to refill old coal mines or it is disposed in extended basins increasing the environmental impact as well as the cost related to its transport. Also there exist convincing interests in the development of non-conventional binders, i.e. alkali-activated cements (geopolimers), which can be a feasible pathway to the valorization of different industrial wastes. When alkali-activated concrete is produced under optimal conditions, it can exhibits similar or even higher mechanical performance and durability when compared to traditional Portland cement concrete. These materials are based on aluminosilicate mineral (precursor) chemically activated by an alkaline solution (activator). Thus, this project is focused in the optimization dosage of bottom ash based geopolymers in pastes and the subsequent mortars production and assessment. Mechanical performance and some permeability properties of the developed geopolyemrs were assessed. The results showed that 15% of Na2O in respect to the bottom ash with 1,0 SiO2/Na2O molar ratio as activator produced more suitable geopolymeric paste. This material was used as a reference system for the development of the proposed project. Also mechanical treatement applied to the BA reduced x% the mean particle size obteining 7 μm and this improved up to ~95% the mechanical performance of the produced geopolymers. The inclusion of Portland cement as a secondary precursor did not have significant effect under the compressive strength when compared to the BA-based systems. Furthermore, the use of other sorces of aluminosilicates, such as aluminium anodizing sludge and spent fluid cracking catalyst, also did not presented any improvement in the analysed geopolimeric systems. BA-based systems activated at 15% of Na2O using an alkali activator solution with a Ms of 1.0 showed the lowest permability and higher mechanical performance.

Les géopolymères sont des matériaux inorganiques fabriqués à partir de composés d’origine naturelle (kaolin, par exemple), ou issus de déchets industriels (cendres volantes, laitiers de hauts fourneaux…). Leurs excellentes propriétés physico-chimiques et mécaniques justifie l’intérêt grandissant qu’ils suscitent dans le domaine de la construction. Toutefois, leur potentiel d’utilisation reste limité en raison de l’emploi, lors de leur préparation, de solutions alcalines fortement concentrées présentant des risques sanitaires importants et d’une difficulté de stockage et transport ; d’où la nécessité d’implémenter des techniques de confection sans solvant. Cette thèse vise à proposer une nouvelle méthode d’élaboration de poudres pré-géopolymères (PGP) par « mécanosynthèse » faciles à transporter et à stocker. Plusieurs matières premières, de différentes natures et compositions chimiques, ont été testées comme précurseurs aluminosilicatés (cendres volantes, métakaolin, laitier de hauts fourneaux et argile) ; elles ont été activées par différents mélanges alcalins (NaOH, KOH, Na2SiO3 et CaO), à des ratios massiques fixés. L’effet de plusieurs paramètres de procédé a été considéré, notamment le temps et la vitesse de broyage. Les poudres pré-géopolymères produites ont été ensuite incorporées dans des formulations de pâtes, de mortiers et d’enrobés bitumineux. Les propriétés physico-chimiques et mécaniques des pâtes produites ont été étudiées. Les résultats obtenus ont été comparés à ceux des pâtes confectionnées par la méthode classique dans les mêmes conditions. La cinétique de la réaction de géopolymérisation des pâtes a été suivie par spectrométrie infrarouge in situ juste après l’hydratation des PGP. Par ailleurs, le procédé de mécanosynthèse indirecte a été utilisé pour améliorer la réactivité de l’argile.Les résultats ont mis en évidence l’efficacité du procédé de mécanosynthèse pour l’élaboration de poudres pré-géopolymères. Celles-ci donnent lieu après hydratation à des pâtes géopolymères avec une structure semblable à celle des géopolymères classiques. Ce procédé a également permis d’améliorer les performances mécaniques des produits géopolymères. Les poudres pré-géopolymères à base d’argile illitique produites par mécanosynthèse indirecte donnent lieu à des pâtes avec une résistance mécanique atteignant 72,5 MPa après 28 jours de cure à 20 °C et 50 % d’humidité relative, contre 12,5 MPa dans le cas classique. Les résultats obtenus sur les mortiers à base de PGP-laitier montrent des résistances mécaniques qui atteignent 38 MPa après 28 jours de cure.Enfin, les résultats préliminaires sur les enrobés bitumineux à base de PGP révèlent une meilleure tenue à l’eau et résistance à l’orniérage, même après 100.000 cycles, que celles des formules de référence sans PGP
Geopolymers are inorganic materials made from compounds of natural origin (kaolin, for example), or from industrial waste (fly ash, blast furnace slag, etc.). Their excellent physicochemical and mechanical properties justify the growing interest they arouse in the construction field. However, their potential of employment remains limited due to the use, during their preparation, of highly concentrated alkaline solutions causing significant health risks and transport storage difficulty; hence it is necessary to implement solvent-free manufacturing techniques.This thesis aims to propose a new producing pre-geopolymer powders (PGP) method by “mechanosynthesis” that are easy to transport and store. Several raw materials, of different types and chemical compositions, were tested as aluminosilicate precursors (fly ash, metakaolin, blast furnace slag and clay); they were activated by different alkaline mixtures (NaOH, KOH, Na2SiO3 and CaO), at fixed mass ratios. The effect of several process parameters was considered, including milling time and speed rotation. The produced pre-geopolymer powders were then incorporated into formulations of pastes, mortars and bituminous mixes. The pastes physicochemical and mechanical properties were studied. The obtained results were compared with those of pastes made by the conventional method under the same conditions. The kinetics of pastes geopolymerization reaction were followed by infrared spectrometry in situ just after the hydration of the PGP. In addition, the indirect mechanosynthesis process has been used to improve the reactivity of clay.The results demonstrated the mechanosynthesis process efficiency for producing the pre-geopolymer powders. These give rise after hydration to geopolymer pastes with a similar structure to that of conventional geopolymers. This process has also helped to improve the mechanical performances of geopolymer products. The pre-geopolymer powders based on illitic clay, produced by indirect mechanosynthesis, give rise to pastes with mechanical resistance reaching 72.5 MPa after 28 curing days at 20 ° C and 50% of relative humidity, against 12.5 MPa for the classic case. The results obtained on slag-based mortars show mechanical strengths reaching 38 MPa after 28 curing daysFinally, the preliminary results on slag PGP-based bituminous mixes reveal better water and rutting resistance, even after 100,000 cycles, than those of the reference formulas without PGP

Mestrado em Engenharia de Materiais
Desenvolveu-se uma parceria entre a Universidade de Aveiro, Ria Blades, S.A. e Saint-Gobain Weber Portugal, S.A. com objetivo de encontrar formas de aproveitamento dos resíduos de fibra de vidro produzidos na Ria Blades, S.A., que atualmente são depositados em aterro. O trabalho incidiu em três produtos-alvo: telas de impermeabilização, argamassas e geopolímeros. No que diz respeito às telas de impermeabilização, de base polimérica (poliuretano), os resíduos foram aplicados como agente de reforço. Estudou-se o efeito da incorporação das fibras na aderência, na resistência à tração e na durabilidade perante ciclos de gelo-degelo. Quando incorporadas fibras de vidro, registou-se um aumento na aderência ao suporte relativamente à amostra padrão e um crescimento (de cerca de 20 vezes) na resistência à tração. Na incorporação em argamassas bastardas, o objetivo foi perceber o efeito da substituição das fibras poliméricas atualmente usadas, pelas fibras de vidro residuais. Estudou-se o efeito na percentagem de ar incorporado e densidade do amassado, bem como a variação de massa e de dimensão, módulo de elasticidade, resistência à compressão e flexão do produto endurecido. A incorporação de fibra de vidro não aparenta prejudicar o desempenho das argamassas, sendo os resultados semelhantes nas amostras padrão. Apesar de as quantidades incorporadas serem apenas de 0,1%, é possível que a utilização destes resíduos tenha impactos economicamente positivos para as duas empresas. Nos geopolímeros, a incorporação das fibras de vidro pretendeu explorar dois efeitos distintos: (i) como ligante, em substituição parcial de metacaulino (até 40% em massa); (ii) como agente de reforço da mistura. Numa primeira fase, foi necessário caracterizar as matérias primas e os resíduos para respeitar as razões molares que asseguram uma maior extensão da reação. Foram avaliadas a densidade aparente, resistência à compressão, absorção de água ao longo do tempo de cura e ainda a resistência à flexão no caso de as fibras funcionarem como agente de reforço. Como substituto parcial do metacaulino verifica-se uma descida na resistência à compressão com o aumento de resíduo de fibra de vidro. No entanto com a otimização da formulação com 20% de fibras de vidro foi possível duplicar o valor da resistência à compressão (> 8MPa). Como agente de reforço, os resultados mostram ganhos de resistência à compressão de 4 vezes quando se incorporam fibras de 6mm de comprimento, relativamente a amostras sem reforço. O uso de fibras mais longas (20mm) é mais eficaz no aumento da resistência à flexão.
A partnership has been developed between the University of Aveiro, Ria Blades, S.A. and Saint-Gobain Weber Portugal, S.A. in order to find a way to recycle the glass-fibre residues produced from Ria Blades, S.A. that are currently being send to landfill. Three possible target-products were exploited: waterproofing membrane, mortars and geopolymers. On the waterproofing membrane, based on polyurethane, the residues were incorporated as reinforcing agents and effects on adhesion, tensile strength and resistance to freeze-thaw cycles were determined. An increase of 20 times on the tensile strength has been registered, relatively to the standard sample. On mortars, the aim was to understand the effect of the substitution of the currently used reinforcing-fibres for the wasted glass-fibres. Fresh-state properties such as the entrained air content and density were evaluated. The effect on relevant hardened-state properties was then studied, including the variation of mass and dimensions, the compressive and flexural strengths, and elastic modulus. The behaviour of the mortars doesn’t seem to be affected by the incorporation of glass-fibres because the results from both the mortars with and without glass-fibres are similar. Although the quantity of incorporated glass-fibres is only around 0,1%, its use may have positive economic benefits for both companies. In geopolymers, the incorporation of wasted glass-fibres aimed to explore two distinct effects: (i) use as binder, partially substituting the metakaolin (up to 40 wt.%); (ii) use as reinforcing agent of common matrixes. On the first stage it was necessary to characterize both the raw materials and the glass-fibres, in order to achieve the desirable molar ratios that assure an extended reaction. Hardened samples were characterized in terms of density, compressive strength and water absorption. In the attempted reinforced geopolymers the flexural strength was additionally tested. When the glass-fibres were used as partial substitute of metakaolin, a drop of the compressive strength was observed for higher contents of glass-fibres. Optimizing the mixture for 20 % of glass-fibres allowed to duplicate the compressive strength (> 8 MPa). When 6 mm glass-fibres were used as a reinforcing agent, the compressive strength increased 4 times when compared to samples without reinforcement. Using 20 mm fibres is the most effective way of improving flexural strength.

碩士
國立臺北科技大學
資源工程研究所
107
Concrete is a common engineering material, which has the advantages of large construction compatibility, low cost, good pressure resistance and good durability. Recently, many high-performance materials have flourished, with special emphasis on carbon reduction and energy saving advantages, such as geopolymer materials, which may be the alternative to new generations of concrete. The evaluation of the engineering characteristics of these materials is based on the test methods of traditional concrete. Many of the test processes are time-consuming and often have a divergent result that the results are very different and cannot be inferred. The evaluation of the engineering properties of high-performance materials requires the development of more appropriate test methods. In order to effectively test the durability of engineering materials, this study aims to accelerate the test of weathering environment and rapid penetration characteristics, develop a test method, select cement mortar and geopolymer mortar samples as samples, establish test operation procedures, and evaluate specimen weathering. The degree of correlation between process permeability characteristics and mechanical property parameters is applied to the durability of cement and inorganic polymerization mortar. The test results show that with the increase of weathering degree, the cement mortar and the different proportion of geopolymer mortar specimens have uniaxial compressive strength reduction, and the permeability coefficient increases. The uniaxial compressive strength and permeability coefficient change negatively. Relevant trends, consistent with previous studies, indicate that this research development test method can provide a rapid assessment of the durability of geopolymer materials and similar high-performance materials. The hydraulic mortar of the test mortar used in this test is subjected to hydraulic penetration after accelerated weathering test. The permeability coefficient is bounded by 10-9 m/s-10-12 m/s, which is about 10 to 100 times. The gas permeability coefficient is between 10-13-10-16 m2, which is about 1-4 times of weathering. The compressive strength is between 13-27 MPa. After the accelerated weathering test, the 4 Mohr marble geopolymer has a hydraulic permeability coefficient bound to 10-13 m/s-10-7 m/s, which is about 106 times, and the gas permeability coefficient is between 10-13 m2. The change is not obvious, and the compressive strength is between 6-20 MPa. After the accelerated weathering test, the 6 Mohr marble geopolymer has a hydraulic permeability coefficient bound to 10-13 m/s-10-7 m/s, which is about 105-106 times, and the gas permeability coefficient is 10-13 m2. During the period, the change is not obvious, and the compressive strength is between 10 and 39 MPa. After the accelerated weathering test, the fly ash geopolymer has a hydraulic permeability coefficient bound to 10-13 m/s-10-7 m/s, which is about 102-105 times, and the gas permeability coefficient is 10-13 m2. During the period, the change is not obvious, and the compressive strength is between 15 and 19 MPa. After the weathering test, the weathering effect of the gas and hydraulic permeability characteristics of the mortar material has a similar trend change. The mechanical properties may be cracked except for the cement mortar which undergoes the hydration reaction, and the strength is deteriorated rapidly. There is an inconspicuous recurve point, which may be caused by leaching, and when the 4 Mohr marble inorganic polymerization mortar is tested after weathering, the test body is easily destroyed, and it is speculated that it may reach the critical value of the test strength. The cement mortar is higher than the sand in the two weathering environments, and the water is higher than the sand. The weathering effect is not obvious. The weathering environment is the same as the water sand and the high, but the weathering frequency increases and rising slowly. In terms of wear effect, the contact area between the sand and the test piece has a certain influence, which indirectly represents the influence of the amount of abrasive sand on the weathering effect. In addition, attempts to add physical property test and chloride ion concentration test, because the cement mortar, inorganic polymerization mortar, the physical properties of the results are not far from the obvious trend change; water-soluble chloride ion concentration, cement mortar with the increase in the number of cycles has an upward trend, 4M marble inorganic polymerization mortar has a downward trend, but the trend of 6M marble inorganic polymerization mortar is not obvious. Therefore, it is necessary to discuss the physical property test and water-soluble chloride ion concentration as the durability evaluation standard.

碩士
國立臺灣科技大學
營建工程系
100
In this study, the slag and metakaolin which contain rich elements of silica and aluminium were used to manufacture three types of composite geopolymer: Type A (70% metakaolin and 30% slag), Type B (30% metakaolin and 70% slag) and Type C (100% slag). Both the sodium hydroxide and sodium silicate solution were used as the activators. Type A composite geopolymer uses three water glass moduli of 0.6, 0.8 and 1.0, three concentrations of alkali activator (11, 13 and 15%) and three water-to-solid ratios (0.55, 0.60 and 0.65), while Types B and C use the water glass moduli of 0.6 and 0.7, the e amount of alkali activator of 9% and 7%, and the water-to-solid ratios of 0.45 and 0.33, respectively. The engineering properties of flowability, initial and final setting times and polymerization temperature at the fresh state and the compressive strength, dynamic elastic and shear moduli, ultrasonic pulse speed, dry shrinkage and thermal properties at hardened for Type A composited geopolymer were studied. But only the engineering properties at hardened state for Types B and C were investigated. The results of study show that: 1. The flowablity of Type A composite geopolymer increases with the increase of the concentration of activator and water-to-solid ratio to reach a best flowability ratio of 125%. The increase of water glass modulus and activator concentration and decrease of water-to-solid ratio tend to reduce the setting times and increase the polymerization temperature with a shortest final setting time of 1.8 hours and a highest temperature of 81oC. 2. The dynamic elastic and shear moduli, ultrasonic pulse speed and thermal conductivity of Types A, B and C geopolymer increase with the increase of sand content with 15%, 96%, 74%, and 11%, 110%, 73%, and 21%, 16%, 9%, and 100%, 48%, 65%, respectively. But both the compressive strength and dry shrinkage decrease with the increase of sand content with 23%, 10%, 22%, and 74%, 35%, 62%, respective. 3. Type A composite geopolymer exhibits a state of uniform shrinkage, but Types B and C show a state of uneven shrinkage.

The developments of ordinary Portland cement (OPC) composites and alkali-activated binder composites have attracted significant attention in the past decade. Different technologies have been proposed to address current drawbacks of these construction materials (e.g. low tensile strength, flexural strength, and brittleness), reduce the amount of cement consumption or replace OPC products for minimizing the environmental impact of construction materials. Among many additives explored to address these problems, graphene-based materials have emerged in the last few years as one of the most promising additives with many exciting results. However, it is still lacking the depth of understanding the influence of key parameters of graphene materials, such as dosages and sizes, on mechanical and durability properties of the composites, and enhancing mechanism of pristine graphene (PRG) in the cement matrix. Moreover, no study has been reported on the influence of graphene oxide (GO) additives on mechanical and durability properties of fly ash (FA)/ ground granulated blast furnace slag (GGBS) alkali-activated binder (AAB) composites prepared with natural sand (NS) or lead smelter slag (LSS) sand cured at ambient temperature. This thesis consists of a series of studies with the focus on addressing current research gaps and making a contribution to the development of next-generation construction materials using graphene additives. The first experimental study on the effect of the dosage of an ultra-large size (56μm) of PRG industrially manufactured by an electrochemical process on compressive and tensile strengths of cement-based mortars reveals that the addition of PRG to mortars improves their mechanical properties, with characteristic concentration dependence. The mortar with 0.07% PRG is identified as the optimal concentration, which provides 34.3% and 26.9% improvement in compressive and tensile strength at 28 days, respectively. However, with the further increases in PRG contents, the enhancement of mechanical properties of mortars is limited due to the impact of the van der Waals force on the sedimentation of PRG suspension. The second study focuses on the size effect of PRG on mechanical strengths of cement-based mortars by considering a variety of PRG sizes, such as 5μm, 43μm, 56μm, and 73μm at the optimal dosage of 0.07% PRG. The study reveals that the mechanical strengths of mortars at 7 and 28 days significantly depend on the sizes of PRG. The mixes with size 56μm and 73μm show a significant influence on both the compressive and tensile strengths of mortars. In contrast, the mix containing size 43μm exhibits a significant increase in tensile strengths only. There are no significant effects on either compressive or tensile strengths for the mix with size 5μm. The third study presents the proposed reinforcing mechanism and optimized dosage of PRG for enhancing mechanical properties of cement-based mortars. The results confirmed that the strengths of the mortars depend on PRG dosages. The size of PRG has a significant effect on the enhancement rate of the mechanical strengths of the mortars, whereas it does not have a significant influence on the optimized PRG dosage for the mechanical strengths of the cement-based mortars. The dosage at 0.07% PRG is identified as the optimized concentration of PRG for enhancing mechanical strengths. The reinforcing mechanism of PRG in the cement matrix highly depends on the surface area of PRG sheets. The fourth and fifth studies show the effect of the dosages, sizes, and densities of PRG as well as design mixes on mechanical and durability properties of cement-based mortars cured at short-term and long-term periods. The study reveals that the addition of PRG to mortars can enhance compressive, flexural, and tensile strengths of mortars at different curing ages. The 0.07% PRG is identified as the optimum dosage for enhancing the mechanical strengths of the mortars. Incorporating a small amount of PRG additives into the mortar can improve its durability, such as water absorptions, voids, sulphate expansion, and water penetration depths. The results of the mix containing PRG size 73μm show the best improvement in the mechanical and durability properties of the mortars, followed by that of size 20μm and then size 40μm. The last experimental study on the influence of GO additive on mechanical and durability properties of AAB mortars containing NS and LSS sand cured at ambient temperature reveals that the increase of GGBS% in AAB results in a significant increase in compressive and tensile strengths, and a decrease in flowability, water absorption and dry shrinkage of the mortars. The results also show that the mortars with 0.05% and 0.1% GO additives provide better mechanical and durability properties compared to the control mixes. The results generated from this thesis show great potential for using PRG and GO as additives in OPC and AAB composites to develop next-generation construction materials. They not only address the current drawbacks of OPC and AAB composites but also reduce the environmental impact of using OPC and NS.
Thesis (Ph.D.) -- University of Adelaide, School of Civil, Environmental and Mining Engineering, 2020

碩士
國立臺北科技大學
資源工程研究所
106
Global warming is a controversial problem worldwide and the cement industry’s annual carbon dioxide emissions account for 5%–7% of the world’s emissions. Therefore, to solve this problem, discovering an alternative material to replace cement is vital. Numerous studies have considered geopolymer as a material that can replace cement in the future because it has excellent mechanical properties. Many resources exist that are rich in silicon and aluminum and can therefore be used as raw material. However, the same type of raw materials from different sources may cause the mechanical properties of geopolymer to differ. Thus, the present study investigated the performance of a geopolymer that was manufactured using coal fly ash from different sources. First, geopolymer paste was produced from different sources of coal fly ash (Linkou, Xingda, and Dalin Power Plants), and the difference between workability and mechanical strength in each series was discussed. Second, we used different sources of coal fly ash and added an aggregate to manufacture a geopolymer mortar that could reduce the effects of IV environmental factors, and then we changed the parameter of the alkali solution (SiO2/Na2O molar ratio and SiO2/Al2O3 molar ratio) to explore the mortar’s influence on workability and its mechanical properties. Finally, we comprehensively discussed workability, mechanical strength, durability, and structural differences in different sources of geopolymer, and investigated the effect of different factors on the main properties through variance analysis. The results indicated that the smaller the particle size of coal fly ash with a short hardening time, the faster the dehydration speed and greater the strength compared with time. The higher the amorphous value of the different sources of fly ash, the greater the reactivity and higher the mechanical strength. In addition, the change in the SiO2/Na2O molar ratio had little effect on the mechanical properties of the alkali solution. Regarding the change of SiO2/Na2O molar ratio, adding the A1 source yielded a longer hardening time of the geopolymer mortar, but the strength and durability of the mortar were greater than those that the Al source were not added to. In terms of structure, it can be observed from FT-IR that the geopolymer produced by different coal fly ash samples had a characteristic shift of Si-O to the position of Si-OT compared with the peak of the raw material. The characteristics that were more obvious denoted that the structure of the geopolymer was produced. According to the variation analysis, the SiO2/Al2O3 molar ratio of the alkali solution was the main influencing factor of hardening time and durability, and the different sources of fly ash were due to the different amorphous values, which affected the compressive strength of the geopolymer mortar.

Because of global environmental concerns for concrete and waste materials and increased awareness of non-renewable natural resources, there is an urgent need to find ways to develop eco-friendly concretes. This is reflected in the large number of recent studies undertaken toward this end. However, the existing studies lack some of main parameters and points, such as the influence of the quality of recycled aggregates, influence of the full replacement of dry constituents with waste-based alternatives, influence of high performance graphene nanomaterials, and influence of the lateral confinement at the material level on the properties of concretes. This thesis contains a series of journal papers focused on the development of eco-friendly and high performance construction materials. In this research the behaviour of different types of concretes and mortars, including recycled aggregate concrete (RAC), geopolymer mortar, waste-based concrete and mortar, and graphene-based cement mortar, is studied. In addition, this thesis presents the behaviour of geopolymer concrete and steel fibre-reinforced concrete (SFRC) under active confinement and high-strength concrete (HSC) under shape memory alloy (SMA) confinement. The experimental study on time-dependent and long-term mechanical properties of RACs shows that high-strength RACs, prepared with full replacement of natural aggregates with recycled concrete aggregates having a high parent concrete strength (110 MPa), exhibit the properties similar to or better than those of companion natural aggregate concretes. Using gene expression programming (GEP) technique, new empirical models are developed to accurately predict mechanical properties of RACs. In addition, analytical studies on RACs reveal that multivariate adaptive regression splines (MARS), M5 model tree (M5Tree), and least squares support vector regression (LSSVR) models provide close predictions of mechanical properties of RACs by accurately capturing influences of key parameters. The experimental study on waste-based concrete reveals that concretes containing ground granulated blast furnace slag (GGBS) at up to 90% cement replacement exhibit nearly similar mechanical properties to the conventional concrete after 28 days of curing age. The experimental studies on geopolymer and waste-based mortars show that mortars with full replacement of sand with lead smelter slag (LSS) and glass sand (GS) and up to 80% replacement of cement with GGBS exhibit nearly similar mechanical properties to the conventional mortar. The study on the influence of graphene oxide (GO) dosage on physiochemical and mechanical properties of cement mortars shows considerable dosage dependence with the optimum dosage of 0.1% GO (by weight of cement) that increases 28-day tensile and compressive strength of the composite by 37.5% and 77.7%, respectively. The study on the influence of oxygen functional groups of graphene on the properties of cement mortars reveals that an addition of 0.1% reduced GO (rGO) prepared by 15 min reduction and 0.2% (wt%) hydrazine results in a maximum enhancement of 45.0% and 83.7% in the 28-day tensile and compressive strengths compared to the plain cement mortar, respectively. The experimental study on the behaviour of ambient- and oven-cured geopolymer concretes under active confinement reveals that oven-cured geopolymers exhibit a less ductile behaviour and lateral dilation than their ambient-cured counterparts. The experimental study on the compressive behaviour of SMA-confined HSCs shows that confinement of HSC by 9.5% prestrained SMA spirals leads to 23.6% higher peak axial stress and 346% higher corresponding axial strain than that of unconfined HSC. The experimental study on the compressive behaviour of actively confined SFRC reveals that an increase in the steel fibre volume fraction leads to an increase in ductility of SFRCs. A finite element (FE) model is also developed to accurately predict the compressive behaviour of fibre-reinforced polymer (FRP)-confined SFRCs. The promising findings of this research point to the possibility of the development of eco-friendly and high performance composite members for structural applications in the construction industry.
Thesis (Ph.D.) -- University of Adelaide, School of Civil, Environmental and Mining Engineering, 2019

Dissertação de mestrado integrado em Engenharia Civil (área de especialização em Perfil de Construções)
Tendo em conta que o consumo de cimento Portland aumenta ano após ano, levando ao aumento das emissões de CO2 na produção do mesmo, torna-se necessário encontrar novos materiais ligantes alternativos mais eco-eficientes. Segundo estudos realizados com materiais de ativação alcalina (também designados por geopolímeros), estes possuem maiores resistências do ponto de vista mecânico, têm maior durabilidade e estabilidade, e atingem estes comportamentos com maior rapidez do que os materiais à base de cimento Portland. Geopolímeros monofásicos é a designação dada para um novo e recente tipo de geopolímeros objeto de estudo nesta dissertação, diferendo dos geopolímeros clássicos por não conterem silicatos de sódio, constituinte responsável por uma elevada pegada carbónica. O presente trabalho de investigação tem como principal objetivo determinar a durabilidade de novas argamassas geopoliméricas, de forma a verificar se são mais ou menos vantajosas relativamente ao cimento Portland e relativamente a outras argamassas geopoliméricas, mas também para servir como termo de comparação para novas misturas que possam surgir nesta área. Nesta dissertação apresentam-se resultados sobre a trabalhabilidade, ensaios de resistência à compressão e à flexão, e sobre alguns parâmetros de durabilidade avaliados com recurso ao ensaio de absorção de água por capilaridade, de absorção de água por imersão, e de resistência ao ataque químico, em argamassas de cimento Portland, argamassas de cimento Portland com cinzas volantes e argamassas de geopolímeros monofásicos. Os resultados obtidos mostram que as argamassas de geopolímeros monofásicos possuem resistências mecânicas inferiores às argamassas de cimento Portland. No entanto as argamassas geopoliméricas com 4% de metacaulino e hidróxido de sódio apresentam desempenhos muito próximos dos resultados obtidos para cimentos Portland, sendo até mesmos superiores no ensaio de absorção de água por imersão.
Given that the consumption of Portland cement increases year after year, leading to an increase in CO2 emissions in the production of the same, it is necessary to find new and eco-efficient alternative binder materials. According to studies performed with materials, alkaline activation (also know as geopolymers), they have greater mechanical resistance, have increased durability and achieve these behaviors faster than Portland cement based materials. One-part geopolymers is the name given to a new and recent type of geopolymers studied in the present dissertation. They differ from classic geopolymers because they do not contain sodium silicate, which is responsible for a high carbon footprint. The current research work had as main objective to assess the durability of the new one-part geopolymeric mortars in order to verify whether they are more or less advantageous than Portland cement mortars or other classic geopolymeric mortars. And also to serve as reference work for future mixtures in this field. This dissertation presents results on workability, compressive and flexural strength and also on some durability parameters assessed with capillary water absorption test, water absorption by immersion test, and resistance to chemical attack in Portland cement mortars, Portland cement mortars with fly ash and one-part geopolymers mortars. The results show that the one-part geopolymeric mortars show mechanical resistances lower than Portland cement mortars, however one-part geopolymeric mortars with 4% metakaolin and sodium hydroxide exhibit performances very similar to the ones obtained with Portland cement mortars, even superior in terms of water absorption by immersion.

Dissertação de mestrado integrado em Engenharia Civil
Os geopolìmeros surgem como materiais com potencial, capazes de responder a alguns dos problemas ambientais criados por materiais como o cimento Portland. A necessidade de reparação de infraestruturas construídas com betão de cimento Portland, que devido às funções que desempenham, apresentam problemas de deterioração precoce, está na origem de impactos tanto económicos como ambientais. Abrindo desta forma, uma porta à criação de revestimentos mais duráveis. Os geopolímeros devido às suas características, tornaramse nesse âmbito um material preferencial. Neste estudo tenta-se perceber então a aplicabilidade dos geopolímeros enquanto material de revestimento capaz de reabilitar infraestruturas industriais, e tendo como alvo principal a proteção dos ácidos. Procedeu-se numa primeira fase a uma escolha das melhores misturas das argamassas geopoliméricas com cinzas volantes e metacaulino, utilizando para isso ensaios de compressão/flexão, absorção de água por imersão e por capilaridade. E numa segunda fase, procedeu-se ao ensaio químico utilizando para isso três ácidos com diferentes concentrações (10%, 20% e 30%) sobre os revestimentos de argamassas e de tintas, bem como de provetes de betão sem qualquer revestimento. Verificou-se que os geopolímeros com cinzas volantes apresentaram resultados muito positivos para concentrações em meio ácido menores que 30%, observando-se em média perdas de massa de 1.2%. O material com melhores resultados foi a resina epoxídica com perdas de 0.8%. Em contraposição apresentou-se o betão convencional com perdas de 11.1% e as argamassas geopoliméricas com metacaulino com 41.3% de perda de massa. Tendo em conta o seu desempenho e principalmente os seus custos, as argamassas geopoliméricas à base de cinzas volantes, revelaram ser uma opção com potencial para reparações de infraestruturas em indústrias que envolvem a produção ou a utilização de ácidos. Apesar da resina epoxídica ter apresentado bons resultados na resistência ao ataque em meio ácido, o seu rácio custo/eficiência é quase 70% superior à solução com revestimento de argamassas geopoliméricas à base de cinzas volantes.
Geopolymers come out as a material fully capable of attending most of the environmental needs arisen by the Portland cement. The need to repair infrastructure constructed using Portland concrete, due to the functions that they perform, lead to problems of premature deterioration witch creates both economic and environmental impacts. This leads to a necessity of coating the support, the geopolymer due to the known properties is a preferred material. This study attempt to test the viability of geopolymer coating as being able to rehabilitate the industrial infrastructure primarily targeting acid attacks protection. Compression / flexion tests and absorption of water by immersion and capillary action were used to select the best mixes of geopolymer based mortars with fly ash and metakaolin. The second fase was carried out using the chemical test for the three more common acids with diferent concentrations (10%, 20% and 30%) on coatings with mortars and paints and on concrete specimens without any cladding. It was verified that the geopolymer with fly ash showed very positive results, for acid concentrations lower than 30%, yielding an average mass loss of 1.2%. The material with the best results was the one with the epoxy resin having a 0.8% loss, in contrast to conventional concrete which had losses of 11.1% and geopolymeric mortar with metakaolin that presented a 41.3% of mass loss. Overall cases sulfuric acid caused the greatest losses, on the other hand hydrochloric acid was where the losses were minor. Attending to the performance and mainly to its costs, the geopolymer mortar with fly ash appear to be an option with potencial to industrial infrastructures repair which concern the production or the usage of acids. In spite of showing good results concerning the resistance to acid attack, the epoxi resin based solution ratio (cost/efficiency) is around 70% superior to the concrete pavement coated with fly ash based geopolymer mortar.

Dissertação de mestrado integrado em Engenharia Civil
O cimento Portland é um elemento fundamental para o fabrico de estruturas de betão. Embora apresente valores de resistência mecânica muito satisfatórios, entre outras características muito positivas, tem uma desvantagem clara de ser um produto muito pouco sustentável. O sector da construção civil é dos sectores mais poluentes a nível mundial, fazendo com que a sustentabilidade do mesmo se torne um fator chave e de interesse para toda a comunidade científica. Como alternativa viável para um produto já muito enraizado na sociedade, surge a obrigação de procurar novos caminhos sustentáveis e apelativos economicamente. Como tal, no âmbito desta dissertação pretende-se colmatar algumas das deficiências do betão, tanto a nível das suas características como a nível ecológico, os materiais obtidos por ativação alcalina surgem como uma alternativa apetecível, incidindo o estudo na sua elevada resistência a altas temperaturas. Foram analisadas seis argamassas geopoliméricas tendo em vista encontrar dois geopolímeros com características idênticas ou superiores às do cimento Portland. Na constituição das argamassas geopoliméricas a molaridade do hidróxido de sódio variou entre 10M, 14M e 18M assim como o ligante, três argamassas compostas por cinzas volantes e nas restantes três com metacaulino, todas elas sujeitas a uma variação de quatro temperaturas (20 ºC, 200 ºC, 500 ºC e 800 ºC). As argamassas geopoliméricas cujo ligante foi o metacaulino apresentam resultados muito interessantes a nível de resistências à flexão sujeitas a temperatura de 20 ºC e 200 ºC, superiores às compostas por cinzas volantes, contudo à medida que a temperatura sobe (500 ºC e 800 ºC), as argamassas com o ligante cinzas volantes apresentam resistências mais elevadas e surpreendentes aos 800 ºC. Em relação à resistência à flexão, os resultados para ambos os ligantes aos 20 ºC e 200 ºC são bastante semelhantes, com a mesma tendência à medida que a temperatura aumenta os geopolímeros constituídos por cinzas volantes têm resistências muito mais consistentes. A análise da microestrutura confirma que as argamassas geopoliméricas à base de cinzas volantes apresentam um maior número de microporos os quais explicam a menor perda de resistência destas quando sujeitas a temperaturas elevadas.
The Portland cement is fundamental for the manufacture of concrete constructions element. Although having values very satisfactory of mechanical strength and other characteristics very positive, has a clear disadvantage of being a little sustainable product. The construction sector is the most polluting industries worldwide, making the sustainability of it becomes a key factor of interest to the entire scientific community. As a viable alternative to a product already deeply rooted in the society, the obligation to look for new sustainable and economically desirable paths arises. As such within this dissertation seek to address some of the deficiencies of the concrete, both in terms of its characteristics as the ecological level, the materials obtained by alkaline activation emerge as a desirable alternative, focusing the study on their high resistance to high temperatures. In the constitution of the geopolymeric mortars molarity of the sodium hydroxide ranged from 10M, 14M and 18M and the binder composed of three fly ash and the remaining three with metakaolin mortars, all subject to a variation of four different temperatures (20 ºC, 200 ºC, 500 ºC and 800 ºC). The geopolymeric mortars whose binder is metakaolin presented very interesting results in terms of flexural subjected to a temperature of 20 °C and 200 °C, higher than those composed of fly ash, however, with the temperature rises (500 °C and 800 °C) the mortar with fly ash binder have higher resistances and surprising for 800 ºC. Regarding the flexural strength, the results for both binders at 20 ºC and 200 °C are quite similar, with the same tendency as the temperature increases geopolymers consisting of fly ash are much more consistent resistance. The microestruture analysis shows that the geopolymeric mortars based on fly ash have a higher number of micropores. This helps to explain why those mortars have a lower strength loss when submitted to high temperatures.

Dissertação de mestrado integrado em Engenharia Civil
Os geopolìmeros surgem como materiais com potencial, capazes de responder a alguns dos problemas ambientais criados por materiais como o cimento Portland. A necessidade de reparação de infraestruturas construídas com betão de cimento Portland, que devido às funções que desempenham, apresentam problemas de deterioração precoce, está na origem de impactos tanto económicos como ambientais. Abrindo desta forma, uma porta à criação de revestimentos mais duráveis. Os geopolímeros devido às suas características, tornaramse nesse âmbito um material preferencial. Neste estudo tenta-se perceber então a aplicabilidade dos geopolímeros enquanto material de revestimento capaz de reabilitar infraestruturas industriais, e tendo como alvo principal a proteção dos ácidos. Procedeu-se numa primeira fase a uma escolha das melhores misturas das argamassas geopoliméricas com cinzas volantes e metacaulino, utilizando para isso ensaios de compressão/flexão, absorção de água por imersão e por capilaridade. E numa segunda fase, procedeu-se ao ensaio químico utilizando para isso três ácidos com diferentes concentrações (10%, 20% e 30%) sobre os revestimentos de argamassas e de tintas, bem como de provetes de betão sem qualquer revestimento. Verificou-se que os geopolímeros com cinzas volantes apresentaram resultados muito positivos para concentrações em meio ácido menores que 30%, observando-se em média perdas de massa de 1.2%. O material com melhores resultados foi a resina epoxídica com perdas de 0.8%. Em contraposição apresentou-se o betão convencional com perdas de 11.1% e as argamassas geopoliméricas com metacaulino com 41.3% de perda de massa. Tendo em conta o seu desempenho e principalmente os seus custos, as argamassas geopoliméricas à base de cinzas volantes, revelaram ser uma opção com potencial para reparações de infraestruturas em indústrias que envolvem a produção ou a utilização de ácidos. Apesar da resina epoxídica ter apresentado bons resultados na resistência ao ataque em meio ácido, o seu rácio custo/eficiência é quase 70% superior à solução com revestimento de argamassas geopoliméricas à base de cinzas volantes.
Geopolymers come out as a material fully capable of attending most of the environmental needs arisen by the Portland cement. The need to repair infrastructure constructed using Portland concrete, due to the functions that they perform, lead to problems of premature deterioration witch creates both economic and environmental impacts. This leads to a necessity of coating the support, the geopolymer due to the known properties is a preferred material. This study attempt to test the viability of geopolymer coating as being able to rehabilitate the industrial infrastructure primarily targeting acid attacks protection. Compression / flexion tests and absorption of water by immersion and capillary action were used to select the best mixes of geopolymer based mortars with fly ash and metakaolin. The second fase was carried out using the chemical test for the three more common acids with diferent concentrations (10%, 20% and 30%) on coatings with mortars and paints and on concrete specimens without any cladding. It was verified that the geopolymer with fly ash showed very positive results, for acid concentrations lower than 30%, yielding an average mass loss of 1.2%. The material with the best results was the one with the epoxy resin having a 0.8% loss, in contrast to conventional concrete which had losses of 11.1% and geopolymeric mortar with metakaolin that presented a 41.3% of mass loss. Overall cases sulfuric acid caused the greatest losses, on the other hand hydrochloric acid was where the losses were minor. Attending to the performance and mainly to its costs, the geopolymer mortar with fly ash appear to be an option with potencial to industrial infrastructures repair which concern the production or the usage of acids. In spite of showing good results concerning the resistance to acid attack, the epoxi resin based solution ratio (cost/efficiency) is around 70% superior to the concrete pavement coated with fly ash based geopolymer mortar.

Dissertação de mestrado integrado em Engenharia Civil
As construções de alvenaria antiga são hoje em dia um foco importante na área da construção dado o seu valor histórico, social e cultural. Assim sendo, este sector tem demonstrado uma maior preocupação na sua preservação com recurso a materiais compósitos para reforço das mesmas. No entanto a informação relativa a estes materiais, é escassa, nomeadamente no que diz respeito à sua aderência ao substrato. Os materiais compósitos, de entre os quais os já conhecidos FRPs, são compostos por uma matriz e fibras. Sendo que nesta dissertação os materiais utilizados são, como substrato, o tijolo, as fibras são metálicas, de vidro e naturais (linho), e a matriz é à base de uma argamassa de cal e uma outra geopolimérica. Com esta tese pretende-se substituir a tradicional matriz de resina, para começar a utilizar matrizes inorgânicas com base em ligantes não cimentícios, de modo a garantir uma boa aderência desta ao substrato, e também de modo a preservar as propriedades das fibras. Ao longo desta dissertação são apresentados ensaios experimentais, com vista a caracterizar o comportamento mecânico dos materiais pertencentes ao compósito, quer individualmente, quer no seu conjunto.
The Ancient Masonry buildings are nowadays an important focus in the construction field, because of their historical, social and cultural importance. Therefore this industry has shown a great concern in its preservation using Composite Materials as reinforcement. However the information about this material is poor, particularly regarding to its bond to the substrate. The Composite Materials, like the well known FRPs, are composed of a matrix and fibers. The used materials in this thesis are, as substrate, the brick, as fibers, metallic, glass and natural (flax) fiber, and the matrix is based in a lime mortar and in a geopolymeric mortar. In this thesis is intended to leave the traditional resin, to start using inorganic matrices based on binders, in order to provide a good bond to the substrate, and also preserving the fibers properties. In the course of this dissertation experimental tests are presented, which aim to characterize the mechanical behavior of the materials that belong to the composite, individually and all together.