Dissertations / Theses on the topic 'Degree of silica hydration'

L’utilisation de ciment à haute teneur en laitier est envisagée dans le cadre du conditionnement des déchets nucléaires. Dans ce contexte, il est nécessaire de connaître les propriétés structurales et de transport des gaz formés par la radiolyse de l’eau contenue dans cette matrice. Selon la littérature, ces propriétés sont impactées par l’ajout de laitier de haut-fourneau. L’objectif de cette thèse est de relier les processus d’hydratation des ciments au laitier aux propriétés de transport des gaz. La première partie de cette étude est consacrée à l’étude de l’hydratation des ciments au laitier. La Résonance Magnétique Nucléaire (RMN) du silicium et de l’aluminium a été utilisée pour suivre l’évolution de la quantité des différentes phases anhydres du clinker (C3S, C2S, C3A et C4AF) et des principaux oxydes de la phase vitreuse du laitier (SiO2, Al2O3, MgO et SO3). La quantité de calcium dissoute provenant du laitier a, quant à elle, été déduite en comparant la quantité de portlandite [Ca(OH)2] mesurée par ATG avec celle calculée par un logiciel de spéciation chimique (Phreeqc). Cette approche a permis de déterminer l’évolution du degré d’hydratation des principaux oxydes de la phase vitreuse du laitier dont une dissolution progressive (comparé au clinker) et incongruente (la vitesse de dissolution des différents oxydes et différente) a ainsi pu être mise en évidence. Cette plus faible réactivité du laitier a pu être mise en relation, pour un temps donné, avec la diminution de la quantité d’eau liée au ciment, de la contraction chimique et de la chaleur dégagée. La prise en compte quantitative de la dissolution des phases du clinker et des oxydes du laitier permet une description plus précise de la minéralogie. La deuxième partie de ce travail porte sur l’évolution de la microstructure et de son influence sur les propriétés de transport en phase gazeuse (diffusion et perméabilité). L’évolution du coefficient de diffusion effectif à l’hélium et à l’azote et de la perméabilité intrinsèque a été suivie au cours du temps et comparée à l’évolution de certaines grandeurs, telles que la porosité globale, le diamètre d’entrée critique, la surface spécifique et le degré de connectivité des pores. Les résultats montrent une diminution du coefficient de diffusion effectif et de la perméabilité au cours du temps, ce qui a pu être relié, pour un même matériau, à la diminution de la porosité totale. Une réduction de ces propriétés avec la teneur croissante de laitier a également été observée. Cette baisse est liée à une diminution de la porosité capillaire et à une augmentation de la nanoporosité, due à une modification de la microstructure des C-S-H. La dernière partie de ce projet concerne la relation entre les processus d’hydratation, la microstructure et les propriétés de transport. Dans ce but, des bilans volumiques des réactions d’hydratation ont été réalisés en considérant de façon indifférenciée ou séparée chaque phase du ciment. La prise en compte séparée des différentes phases du ciment permet d’évaluer avec une précision de 10 % la porosité totale, la teneur en eau liée et le volume de contraction chimique. Cette description permet d’expliquer les variations des propriétés de transport d’un même matériau dans la durée. Pour établir ce lien au cours du temps et pour tous les ciments, le volume apparent des C-S-H a été recalculé pour rendre compte de la microstructure de ces hydrates
Cements with high slag content are currently studied as possible candidate for nuclear waste containment materials. In this context it is important to know their microstructure and the transport properties (permeability and diffusion) of the gases that are formed by the radiolysis of the water present in this material. According to literature, these properties are strongly impacted by the addition of blast furnace slag. The aim of this work is to correlate the hydration processes of slag blended cements with their transport properties. In the first part of this work, the hydration of the slag blended cements, for which only few results have been reported to date, has been studied. Silicon-29 and aluminium-27 Magic-Angle Spinning Nuclear Magnetic Resonance (MAS NMR) were used to follow the variations of anhydrous phases of clinker (C3S, C2S, C3A and C4AF) and of the main oxides of the slag (SiO2, Al2O3, CaO, MgO and SO3). The quantity of calcium dissolved from slag was deduced by fitting the quantity of portlandite [Ca(OH)2] calculated by a geochemical software (PHREEQC - coupled to a thermodynamic database) with TGA measurements. Our approach enabled the evolution of the hydration degree (percentage of reacted material) of various oxides of slag to be determined. A progressive and an incongruent dissolution (the rate of dissolution of the oxides is different) of the slag is observed. The low reactivity of slag could be linked, at a hydration time, to a lower content of bound water, chemical shrinkage and heat of hydration. Quantitatively accounting for the dissolution of clinker and oxide of slag yields a more accurate description of the hydration process. The second part of this work is focused on the microstructure evolution and its influence on the transport properties (diffusion and permeability). Time-evolution of the diffusion coefficients and the intrinsic permeability could be monitored and were then compared to that of the microstructure (global porosity, pore entry size distribution, specific surface area and the degree of connectivity). The results showed a decrease in the diffusion coefficient and permeability over time which is due to the progressive filling of the porosity. A decrease of these parameters with the slag content increasing was also observed. This is a consequence of the diminution of the capillary porosity and augmentation of the nanoporosity resulting from changes in the microstructure of C-S-H. The last part concerns the relation between the hydration processes, the microstructure and the transport properties. To this aim, volumetric balances of reactions involved in the hydration processes were made by considering globally or specifically the hydration of the different phases. Accounting for the hydration of each phase of the cement allowed us to determine the global porosity, the bound water content and the chemical shrinkage with accuracy of the order of 10 %. This description allows the understanding of the transport properties variations in time for a same material To establish this time evolutions for all the cements, the apparent volume of C-S-H was recalculated to account for the microstructure of these hydrates

The response of the surface of the Soda Lime Silica float glass to contact was studied by means of instrumented indentation. The research was focused on two specific conditions to which the glass can be exposed during manufacturing and use, first, the change in the hardness and elastic modulus of the near surface of glass exposed to different periods of accelerated weathering at 40°C and 95% relative humidity, and second, changes in the mechanical properties at 520, 540 and 560°C, the latter being the glass transition temperature of this type of glass. There is an extensive literature about the effects that weathering has on the chemical composition of the air and tin sides surfaces of float glass. Nevertheless, research into the mechanical properties of weathered glass is rather limited. In this study it was found that the air side of the float glass showed an evolution of the nanoindentation hardness and elastic modulus with the exposure time, while in the tin side, the change was almost negligible under the same experimental conditions. Regarding the contact at elevated temperature on glass, it is possible to find several studies in which hardness is reported over a wide range of temperatures from below 0 up to 700°C. There are discrepancies in the reported results at high temperatures due to the different experimental conditions used by the researchers. This study investigated the effect of the testing parameters such as loading and unloading rate, dwell time, and temperature. The creep behaviour was also studied using mechanical models with Maxwell and Kelvin elements. Such models were fitted to the creep curves and explained well the viscoelastic behaviour near the glass transition temperature. The experiments were carried out on a specially developed apparatus, which has the ability to perform micro and macro-indentations with Vickers and Hertzian indenters from room temperature up to 560°C.

It is increasingly important to identify the nature of the interfacial water in biology in order to explain how biological functions and systems work. It is not simply a matter of which biomolecules are present in a cell, but also of how these biomolecules interact with one another. This body of work uses neutron scattering techniques to explain the nature of the vibrational dynamics of water interacting with biomolecules and systems that mimic the biological molecular crowding environment of a cell. Recent work in science has seen the synthesis of periodic mesoporous organosilicas with organic groups attached. In the first paper in this thesis, the use of one of these materials is highlighted to look at confined water, equivalent to the water found in a crowded cellular environment. Here it is shown that the properties of the water within the pores and water molecules around the surface were shown to be different and then identified as interfacial and bulk water respectively. In order to develop the investigation of interfacial water with biological matter, it seemed appropriate to start with the most basic molecules, amino acids. The second paper presents a complete survey of the 20 biologically important amino acids using one of the world's highest resolution neutron scattering spectrometer (TOSCA at ISIS, Rutherford Appleton Laboratory). Computer simulation of the experimental work through molecular dynamics, allows many vibrational modes to be assigned for the first time and correlated with the broader vibrational peaks previously observed for proteins. Comparison of the dry states with the hydrated states of amino acids, gives some insight into the sites within the amino acid side chains where water molecules are likely to bind. For serine this is the hydroxyl group in the side chain. The third paper focuses on IINS data of serine in more detail and discusses several low energy vibrational modes that have been assigned and for the first time, shows how the presence of water molecules changes the dynamic behaviour of librational and torsional modes differently. The combination of these studies allows a clearer picture of how water in biology interacts with biomolecules and of the importance of water to our existence.

Doctor of Philosophy
Department of Civil Engineering
Kyle A. Riding
Finely ground glass has the potential for pozzolanic reactivity and can serve as a supplementary cementitious material (SCM). Glass reaction kinetics depends on both temperature and glass composition. Uniform composition, amorphous nature, and high silica content of glass make ground glass an ideal material for studying the effects of glass type and particle size on reactivity at different temperature. This study focuses on how three narrow size ranges of clear and green glass cullet, 63–75 [mu]m, 25–38 [mu]m, and smaller than 25 [mu]m, as well as combination of glass types and particle sizes affects the microstructure and performance properties of cementitious systems containing glass cullet as a SCM. Isothermal calorimetry, chemical shrinkage, thermogravimetric analysis (TGA), quantitative analysis of X-ray diffraction (XRD), and analysis of scanning electron microscope (SEM) images in backscattered (BS) mode were used to quantify the cement reaction kinetics and microstructure. Additionally, compressive strength and water sorptivity experiments were performed on mortar samples to correlate reactivity of cementitious materials containing glass to the performance of cementitious mixtures. A recently-developed modeling platform called “[mu]ic the model” was used to simulated pozzolanic reactivity of single type and fraction size and combined types and particle sizes of finely ground glass. Results showed that ground glass exhibits pozzolanic properties, especially when particles of clear and green glass below 25 [mu]m and their combination were used at elevated temperatures, reflecting that glass cullet is a temperature-sensitive SCM. Moreover, glass composition was seen to have a large impact on reactivity. In this study, green glass showed higher reactivity than clear glass. Results also revealed that the simultaneous effect of sizes and types of glass cullet (surface area) on the degree of hydration of glass particles can be accounted for through a linear addition, reflecting that the surface area would significantly affect glass cullet reactivity and that the effects of SCM material interaction on reaction kinetics were minimal. However, mechanical properties of cementitious systems containing combined glass types and sizes behaved differently, as they followed the weaker portion of the two particles. This behavior was attributed to the pores sizes, distruibution, and connectiity. Simulations of combined glass types and sizes showed that more work on microstructural models is needed to properly model the reactivity of mixed glass particle systems.

In this thesis we present the synthesis and characterization of different types of ruthenium complexes containing N-donor ligands together with dmso, Cl and H2O ligands, along with their complete characterization through spectroscopic and electrochemical techniques. The complexes have been evaluated as catalysts for olefin epoxidation and nitrile hydration in homogeneous phase. On the other hand, taking into account the importance and advantages of the heterogeneous catalysis, we have carried out the immobilization of some of these complexes on silica-type supports and we have evaluated their catalytic activity, comparing them with the analogous homogeneous systems. It is outstanding the activity of complexes with dmso and pyrazolyl ligands in nitrile hydration to the amide products using water as solvent. The heterogeneous Ru-OH2 systems have been tested in olefin epoxidation and have been reused for several runs maintaining high values of selectivity for the epoxide.
En aquesta tesi es presenta la síntesi de diferents tipus de complexos de ruteni que contenen lligands N-donadors en combinació amb lligands dmso, Cl i H2O, i la seva completa caracterització mitjançant tècniques espectroscòpiques i electroquímiques. Els complexos han estat avaluats com a catalitzadors en epoxidació d'olefines i hidròlisi de nitrils en fase homogènia. Per altra banda, tenint en compte la importància i els avantatges de la catàlisi heterogènia, s’ha dut a terme la immobilització d’alguns d’aquests complexos sobre suports tipus sílice i se n'ha avaluat l'activitat catalítica, comparant-los amb els anàlegs en fase homogènia. És destacable l'activitat dels complexos amb lligands dmso i pirazole en la hidròlisi de nitrils a amides en aigua com a dissolvent. Els sistemes Ru-OH2 heterogenis s'han avaluat en l'epoxidació d'olefines i s'han pogut reutilitzar durant diversos cicles mantenint alts valors de selectivitat per l'epòxid.

Les ciments sulfoalumineux sont des liants hydrauliques qui, jusqu’aujourd’hui ne sont pas normalisés et ne possèdent donc pas une composition fixe. La teneur en ye’elimite – la phase principale de ce ciment- peut varier de 5 à 70 %. Or la composition du ciment sulfoalumineux (la composition du clinker ainsi que le pourcentage de gypse ajouté) est un paramètre critique qui contrôle sa réactivité, ses performances mécaniques, ainsi que sa durabilité. L’objectif principal de cette thèse est donc l’étude de l’influence de la composition des ciments sulfoalumineux sur leurs propriétés techniques, telles que les performances mécaniques et durabilité. Trois axes principaux ont été abordés. Tout d’abord une étude de l’influence de la composition du ciment sulfoalumineux (25-75 % en masse de ye’elimite) sur ses propriétés hydrauliques et mécaniques ainsi que sur la valeur limite en élément trace (Zn) a été menée. Dans ce but trois ciment sulfoalumineux (25, 50 et 75 % en masse de ye’elimite) ont été synthétisés. Ensuite l’effet de la variabilité de ce ciment sur sa durabilité dans l’eau pure et sulfatée a été investigué par rapport à un ciment sulfoalumineux commercial. Enfin, une étude des potentialités du ciment sulfoalumineux commercial à inhiber la réaction alcali silice dans les mortiers, lors de l’utilisation d’un granulat réactif (Silex), a été conduite. Il en résulte de cette étude qu’une augmentation de taux de ye’elimite dans le ciment sulfoalumineux engendre une augmentation des performances mécaniques. La valeur limite en Zn est de 0,3 % indépendamment de la composition du ciment sulfoalumineux. Par contre cette dernière influence la durabilité de ces ciments. Les résultats révèlent que même si la formulation contenant 75 % en ye’elimite confère les meilleures performances mécaniques, sa durabilité était la plus faible due à l’absence de stratlingite dans sa matrice cimentaire. Enfin, l’utilisation du ciment sulfoalumineux présente des bonnes potentialités à inhiber la réaction alcali silice
Sulfoaluminate cements are hydraulic binders that, until today, are not standardized and therefore do not have a fixed composition. The content of ye'elimite - the main compound of this cement - can vary from 5 to 70 %. However, the composition of sulfoaluminate cement (clinker composition as well as the percentage of added gypsum) is a critical parameter that controls its reactivity, mechanical performance, as well as its durability. The main objective of this thesis is to study the influence of sulfoaluminate cements composition on their technical properties, such as mechanical performances and durability. Three main axes were discussed in this work. First, the influence of the sulfoaluminate cement composition (25-75 wt. % of ye'elimite) on its hydraulic and mechanical properties, as well as on the threshold limit of Zn, was studied. For this purpose three sulfoaluminate cements (25, 50 and 75 wt. % of ye'elimite) were synthesized. Then the effect of the variability of this cement on its durability in pure and sulphated water was investigated compared to a commercial sulfoaluminate cement. Finally, a study of the potentialities of commercial sulfoaluminate cement to inhibit the alkali silica reaction in mortars, when using a reactive aggregate (flint), was conducted. This study reveals that an increase in ye'elimite content in the sulfoaluminate cement increases the mechanical performance. The threshold limit of Zn is 0.3 % independently of the sulfoaluminate cement composition. Contrariwise, the sulfoaluminate cement composition influences the durability of these cements. Although the formulation containing 75 % of ye’elimite gives the best mechanical performances, its durability was lowest due to the absence of stratlingite in its cement matrix. Finally, the use of sulfoaluminate cement has good potential towards the inhibition of the alkali silica reaction

Analyse des modifications de la structure interne du mortier induites par l'introduction des fibres et determination de leur influence sur les proprietes mecaniques du mortier en flexion. Des fiches en paquets introduites dans le mortier se dispersent lors du malaxage en fibres individuelles espacees de quelques microns. Ces espaces, tres peu accessibles aux particules anhydres du ciment sont partiellement remplis par des hydrates. Ils rendent le mortier tres permeable aux fluides et influent directement sur son module d'elasticite en flexion qui diminue avec le pourcentage de fibres. L'effet d'armature des fibres se traduit par une augmentation de la resistance et de l'allongement a la rupture du mortier. De la fumee de silice dispersee a l'aide d'un fluidifiant reduit la porosite entre les fibres et augmente ainsi le module d'elasticite et sa resistance a la rupture

This work is devoted to study the influence of the composition on mechanical properties of high performance concret based on portland cement. 29 samples of high performance concrete (HPC) warying in composition were prepared. The constituents used for HPC preparation were: cement Aalborg White, silica fume, finelly ground blast furnace slag, finelly ground silica, calcinated bauxite and polycarboxylate based superplasticizer. The mechanical parameters (flexural and compressive strength) of the samples were observed after 7 and 28 days of moist curing. Compressive strength values after 28 days were in the range of 92 to 194 MPa and the flexural strength values were in the range of 7 to 23 MPa (without using of fiber reinforcement). The graphs showing mechanical parameters depending on the mixture composition were constructed and consequently evaluated.

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Biogenic silica is abundantly preserved in sediment and is found in diatoms and many higher plants. The isotopic composition (δ18Osilica) of biogenic silica is used widely in paleoclimate research to infer conditions in which the organism grew. However, previous studies show that secondary alterations within the matrix of biogenic silica complicate the structural and geochemical analysis of silica. This study investigates how the hydrated structure of silica changes at different temperature with time. A statistical model is constructed that quantifies the degree of silica hydration (Q4/Q3) by calibrating Fourier transform infrared (FTIR) measurements against nuclear magnetic resonance. This study also conducts an investigation of various oxidation techniques to find an optimal method to be used to remove organics within biogenic silica, although residual contamination proved challenging to remove in most cases. These contaminants hinder the quantification of silica hydration using FTIR which is also used in the statistical modelling of Q4/Q3 measurements. The experimental results showed a relationship between time and the relative increase of the relative hydroxylation/dehydroxylation of biogenic silica. However, silica condensation is not a linear reaction, but reversible, potentially implying that the structure of silica readily undergoes temporary absorption/desorption at its surface in the presence of water.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 2016

Silica fume is a widely used pozzolan in the concrete industry that has been shown to have numerous benefits for concrete including improved mechanical properties, refined pore structure, and densification of the interfacial transition zone between paste and aggregates. Traditionally, silica fume is used as a 5% to 10% replacement of cement; however, newer classes of higher strength concretes use silica fume contents of 30% or greater. At these high silica fume contents, many detrimental effects, such as poor workability and inconsistent strength development, become much more prominent.

In order to understand the fundamental reasons why high silica fume contents can have these detrimental effects on concrete mixtures, eight commercially available silica fumes were characterized for their physical and chemical properties. These included traditional properties such as density, particle size, and surface area. A non-traditional property, absorption capacity, was also determined. These properties or raw material characteristics were then related to the hydration and rheological behavior of pastes and concrete mixtures. Other tests were performed including isothermal calorimetry, which showed that each silica fume reacted differently than other silica fumes when exposed to the same reactive environment. Traditional hydration models for ordinary portland cement were expanded to include the effects that silica fumes have on water consumption, volumes of hydration products, and final degree of hydration.

As a result of this research, it was determined necessary to account for the volume and surface area of unhydrated cement and unreacted silica fume particles in water-starved mixture proportions. An adjustment factor was developed to more accurately apply the results from hydration modeling. By combining the results from hydration modeling with the surface area adjustments, an analytical model was developed to determine the thickness of paste (hydration products and capillary water) that surrounds all of the inert and unreacted particles in the system. This model, denoted as the “Paste Thickness Model,” was shown to be a strong predictor of compressive strength results. The results of this research suggest that increasing the paste thickness decreases the expected compressive strength of concretes at ages or states of hydration.

The rheological behavior of cement pastes containing silica fume was studied using a rotational rheometer. The Herschel-Bulkley model was fit to the rheological data to characterize the rheological behavior. A multilinear model was developed to relate the specific surface area of the silica fume, water content, and silica fume content to the Herschel-Bulkley rate index. The Herschel-Bulkley rate index is practically related to the ease at which the paste mixes. This multilinear model was shown to have strong predictive capability when used on randomly generated paste compositions.

Additionally, an analytical model was developed that defines a single parameter, idealized as the thickness of water surrounding each particle in the cementitious system. This model, denoted as the “Water Thickness Model,” incorporated the absorption capacity of silica fumes discovered during the characterization phase of this study and was shown to correlate strongly with the Herschel-Bulkley rate index. The Water Thickness Model demonstrates how small changes in water content can have a drastic effect on the rheology of low w/c or high silica fume content pastes due to the combined effects of surface area and absorption. The effect of additional water on higher w/c mixtures is significantly less.

Raman spectroscopic observations of the characteristics and dissociation of methane hydrate were carried out on hydrates synthesized in silica sands with particle sizes of 53-75 μm, 90-106 μm, 106-150 μm, and 150-180 μm. The results obtained indicate that methane hydrates formed in silica sands had similar characteristics regarding cage occupancy and hydration number (5.99) to bulk hydrate, indicative of no influence of particle size on hydrate composition. During hydrate dissociation, the change in average intensity ratio of large to small cages were generally consistent with that of bulk hydrate but dropped dramatically after a certain time, and this turning point seems to be related to the particle size of silica sands.

Dissertação de Mestrado Integrado em Engenharia Química apresentada à Faculdade de Ciências e Tecnologia
The present work aims to optimize a simple and economical method of synthesis of silica nanoparticles and to study the influence of their addition on cement formulations in terms of physical, chemical, thermal and mechanical properties, in order to improve them .Regarding the synthesis of nanoparticles, a sol-gel method was used, using sodium silicate (recognized as an economically accessible precursor) and hydrochloric acid, with parameters such as temperature and time of synthesis, as well as the volume of acid used being studied. and the concentration of the precursor. All the synthesized particles were characterized in terms of their size and zeta potential. In all tests performed, their nanometric size was confirmed, obtaining average sizes between 30 and 100 nm. Regarding the stability of the dispersions, all of them were characterized as being stable, obtaining values of zeta potential between -30 and -60 mV. The test where the best results were found in these two properties (test 3) had the following synthesis parameters: synthesis temperature of 27ºC, synthesis time of 5 minutes, precursor concentration of 6% by weight, and acid volume of 15 mL .The nanoparticles were further characterized using FTIR and SEM. Through infrared spectroscopy it was possible to identify the main functional groups present and prove the effectiveness of the washing step. With the microscopic analysis of the nanoparticles it was possible to confirm their nanometric size, as well as to obtain information about the geometry of the particles. Regarding the effects of applying nanoparticles in cement mortars, physical, chemical, thermal and mechanical properties were studied. A thermogravimetric analysis was carried out on one of the specimens, which allowed the improvement in the hydration of the test piece with nanoparticles. The thermal conductivity of the specimens showed a tendency to decrease with the addition of the nanoparticles as intended, reaching a decrease of about 11% for one of the specimens produced. Regarding the microstructure and the mechanical properties of the specimens, the addition of nanoparticles resulted in an improvement of these properties, with the best result being obtained for the test where the nanoparticles with smaller sizes were produced, reaching 11% and 70%, in relation to Young's modulus and maximum compressive strength, respectively.
O presente trabalho tem como objetivos a otimização de um método de síntese simples e económico de nanopartículas de sílica e o estudo da influência da sua adição em formulações de cimento ao nível das propriedades físicas, químicas, térmicas e mecânicas, com o intuito de as melhorar. Em relação à síntese das nanopartículas, foi utilizado um método sol-gel, com recurso a silicato de sódio (reconhecido como precursor economicamente acessível) e ácido clorídrico, sendo estudados parâmetros como a temperatura e tempo de síntese, bem como o volume de ácido usado e a concentração do precursor. Todas as partículas sintetizadas foram caracterizadas relativamente ao seu tamanho e ao potencial zeta. Em todos os ensaios realizados confirmou-se o seu tamanho nanométrico, obtendo-se tamanhos médios entre 30 e 100 nm. Em relação à estabilidade das dispersões, todas elas se caracterizaram como sendo estáveis, obtendo-se valores de potencial zeta entre -30 e -60 mV. O ensaio onde se verificaram melhores resultados nestas duas propriedades (ensaio 3) teve os seguintes parâmetros de síntese: temperatura de síntese de 27ºC, tempo de síntese de 5 minutos, concentração de precursor de 6% em massa, e volume de ácido de 15 mL.As nanopartículas foram ainda caracterizadas com recurso a espetroscopia de infravermelho por transformada de Fourier e microscopia eletrónica de varrimento. Através da espetroscopia de infravermelho foi possível identificar os principais grupos funcionais presentes e comprovar a eficácia da etapa de lavagem. Com a análise microscópica das nanopartículas foi possível confirmar o seu tamanho nanométrico, bem como obter informações acerca da geometria das partículas.Em relação aos efeitos da aplicação das nanopartículas em argamassas, foram estudadas propriedades físicas, químicas, térmicas e mecânicas. A um dos provetes foi realizada uma análise termogravimétrica, sendo que esta permitiu comprovar a melhoria ao nível da hidratação do provete com nanopartículas. A condutividade térmica dos provetes revelou uma tendência para diminuir com a adição das nanopartículas como era pretendido, atingindo uma diminuição de cerca de 11% para um dos provetes produzidos. Em relação à microestrutura e às propriedades mecânicas dos provetes, a adição de nanopartículas traduziu-se numa melhoria destas propriedades, sendo o melhor resultado obtido para o ensaio onde se produziram as nanopartículas com tamanhos inferiores, atingindo os 11% e 70%, em relação ao módulo de Young e à resistência máxima à compressão, respetivamente.