abstract: Alkali-activated aluminosilicates, commonly known as "geopolymers", are being increasingly studied as a potential replacement for Portland cement. These binders use an alkaline activator, typically alkali silicates, alkali hydroxides or a combination of both along with a silica-and-alumina rich material, such as fly ash or slag, to form a final product with properties comparable to or better than those of ordinary Portland cement. The kinetics of alkali activation is highly dependent on the chemical composition of the binder material and the activator concentration. The influence of binder composition (slag, fly ash or both), different levels of alkalinity, expressed using the ratios of Na2O-to-binders (n) and activator SiO2-to-Na2O ratios (Ms), on the early age behavior in sodium silicate solution (waterglass) activated fly ash-slag blended systems is discussed in this thesis. Optimal binder composition and the n values are selected based on the setting times. Higher activator alkalinity (n value) is required when the amount of slag in the fly ash-slag blended mixtures is reduced. Isothermal calorimetry is performed to evaluate the early age hydration process and to understand the reaction kinetics of the alkali activated systems. The differences in the calorimetric signatures between waterglass activated slag and fly ash-slag blends facilitate an understanding of the impact of the binder composition on the reaction rates. Kinetic modeling is used to quantify the differences in reaction kinetics using the Exponential as well as the Knudsen method. The influence of temperature on the reaction kinetics of activated slag and fly ash-slag blends based on the hydration parameters are discussed. Very high compressive strengths can be obtained both at early ages as well as later ages (more than 70 MPa) with waterglass activated slag mortars. Compressive strength decreases with the increase in the fly ash content. A qualitative evidence of leaching is presented through the electrical conductivity changes in the saturating solution. The impact of leaching and the strength loss is found to be generally higher for the mixtures made using a higher activator Ms and a higher n value. Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR) is used to obtain information about the reaction products. / Dissertation/Thesis / M.S. Civil Engineering 2012

Buildings construction and realization of public infrastructures have always been a primary need in the human society, developing low cost and user-friendly materials which also encounter safety and durability requirements. Portland cement is the most used material in construction industry from the industrial revolution up to date, but the raising concerns related to the climate change are pushing the governments worldwide to replace it with more eco-friendly and greener materials. Geopolymers are considered to be best alternatives to Portland cement in construction industry, but issues related to cost and mechanical properties are still hindering the commercialization of this material. Geopolymer incorporating wastes is one of the solutions. Fly ash, a thermal power plant by-product, and borosilicate glass, a recycled glass from pharmaceutical vials, are suitable candidates in geopolymers activation. NMR and FTIR spectroscopies demonstrated that borates from borosilicate glass are active compounds in geopolymerization, substituting the alumina is its role, composing a B-Al-Si network never observed before. Various fly ash and borosilicate glass weight contents were studied in terms of mechanical properties (compression test, 3-point bending test). It was found that fly ash 55 wt.% and borosilicate 45 wt.% composition activated in 13 M NaOH solution holds the best compressive and flexural strength (45 and 4 MPa respectively), 25% stronger than similar counterparts found in literature. Cellulose fibres in different weight contents were dispersed into the geopolymeric paste to produce geopolymer composites, with the aim to render the material more suitable for structural applications. 3-point bending test showed an improvement of the flexural strength of about 165% (12 MPa), while the chevron notch method displayed a fracture toughness of 0.7 MPam1/2, in line with the results of geopolymer composites found in literature. In this thesis work, fly ash was also successfully densified in 3 M NaOH solution and distilled water through a new method based on hydraulic pressure, called hydro-pressure sintering. This innovative technology involves a drastic reduction of NaOH utilization in geopolymerization, rendering the material more eco-friendly. XRD spectroscopy conducted on produced samples revealed a higher formation of crystals, most likely induced by the application of hydraulic pressure (450 MPa).

Evaluation of physical and chemical properties of geopolymer composites based on alkali aktivated metakaoline and silicate oxide.

worse than degradation at the crown of the sewer pipe. Furthermore, results from this study show that high resistance under the static acid corrosion exposure condition cannot be extended to mean high resistance under the erosion-corrosion exposure condition for some concrete mixes. In this study, the static HCl test and the dynamic HCl test were used to measure the resistance of concrete mixes under the static corrosion exposure condition and erosion-corrosion exposure condition respectively. However, concretes that exhibited high resistance to the erosion-corrosion exposure condition were consistent in exhibiting high resistance to the static corrosion exposure condition. This finding is consistent with the sequence of corrosion processes in MIC, wherein dissolution of the concrete components occurs before the precipitation of corrosion products. Therefore, it expected that high resistance in the dynamic acid test (i.e. resistance to dissolution) implies high resistance in the static test, which measures the combined resistance of dissolution and resistance emanating from corrosion products. Both static and dynamic acid corrosion tests revealed that the geopolymer concretes tested in this study outperformed PC and CAC concretes. Results from the static HCl test showed that GP-ferro-quartz concrete, the most durable concrete specimen, provided a 69-fold improvement in resistance when compared to PC-dolomite mixes (control #1) and a 4.72-fold improvement in resistance when compared to CAC-dolomite mixes (control #2). Results from the dynamic HCl test show that the GP-ferro-quartz mix provided a 180-fold increase in resistance when compared to the PC-dolomite mix and a 275-fold increase when compared to CAC-dolomite mix. The CACdolomite mix was found to have the lowest resistance to the erosive-corrosive exposure conditions of the dynamic HCl test. Thus, in terms of the concrete MIC resistance properties identified in this study, it is suggested that the CAC-dolomite mix had poor kinetic resistance to dissolution. However, under the static acid test (static corrosion exposure condition), the CAC-dolomite mix performed better than the PC-dolomite mix and GP-dolomite mix. CAC-dolomite concrete performed inferiorly only to the set of GP-siliceous-aggregate mixes in the static HCl test. The difference in the performance of CAC-dolomite concrete performance between the static and dynamic test is largely attributed to the formation of alumina gel, an acid corrosion product of CAC hardened paste, which envelopes the concrete specimen and reduces the rate of surface corrosion in the static HCl test. However, under v the dynamic HCl test, the gel layer is brushed off the surface of the concrete specimen rendering it ineffective in protecting the concrete specimen from corrosion. Previous research on the acid attack of concrete posits that the chemical make-up of concrete materials has a strong bearing on corrosion behaviour. To this end, various measures have been suggested such as the ratio of calcium to silicon (Ca/Si) in concrete. The approach utilised in this study was to calculate the “basicity value” which provides the ratio of major basic to acidic oxides found in the concrete. XRF analysis of the hardened cement pastes and the 5 aggregate types used in the experiments enabled the calculation of basicity values. The combined basicity value for concrete specimens was determined by proportionally summing (according to mass) the basicity values of the aggregate and hardened cement paste parts. A strongly correlated linear relationship between the basicity value of concrete and the corrosion rate from the dynamic HCl test was established. This empirical relationship warrants further investigation and verification, as it would, in principle provide a means to estimate the dissolution rate of concrete by calculating its basicity instead of undertaking laboratory acid tests. Basicity was also found to be useful in determining the corrosion compatibility of binder type and aggregate types. It was found that the difference between the basicity value of hardened cement paste and the basicity value of the aggregate was useful in determining the type and extent of preferential corrosion of a concrete specimen tested under the dynamic HCl test. For ease of reading, this difference was called the “basicity differential”. By visually assessing corroded concrete specimens from the dynamic HCl test, it is was possible to determine whether the hardened cement paste or aggregate component was preferentially corroded, and to gauge the extent of preferential corrosion visually. GP-ferro-quartz and GP-granite concretes had the lowest levels of preferential corrosion which corresponded to their low basicity differential values. In contrast, CAC-dolomite concrete had the highest basicity discrepancy which corresponded visually to a high preferential corrosion of the hardened cement paste. Mineralogical analysis via XRD, found that the hardened cement pastes of the three binder types consisted mainly of amorphous phases (>70%). The crystalline phase of the geopolymer hardened cement paste was mostly constituted by insoluble minerals such as mullite. This partially explains the higher corrosion resistance of geopolymer concretes. However, a more comprehensive explanation needs to include analysis of the amorphous phases, which fell outside the scope of this study. SEM analysis of HCl corroded geopolymer hardened cement paste found that fly ash spheres embedded within the geopolymer matrix were preferentially corroded. This indicates that fly ash content negatively affected the rate of corrosion of the geopolymer hardened cement paste. Furthermore, SEM analysis showed that the geopolymer matrix surrounding the fly ash spheres was relatively intact.

Concrete is by far the most widely used construction material worldwide in terms of volume, and so has a huge impact on the environment, with consequences for sustainable development. Portland cement is one of the most energy-intensive materials of construction, and is responsible for some emissions of carbon dioxide — the main greenhouse gas causing global warming. Efforts are being made in the construction industry to address these by utilising supplementary materials and developing alternative binders in concrete; the application of geopolymer technology is one such alternative. Indeed, geopolymers have emerged as novel engineering materials with considerable promise as binders in the manufacture of concrete. Apart from their known technical attributes, such as superior chemical and mechanical properties, geopolymers also have a smaller greenhouse footprint than Portland cement binders. / Research on the development, manufacture, behaviour and applications of low calcium fly ash-based geopolymer concrete has been carried out at Curtin University of Technology since 2001. Past studies of the structural behaviour of reinforced fly ash-based geopolymer concrete members have covered the flexural behaviour of members. Further studies are needed to investigate other aspects of the structural behaviour of geopolymer concrete. Design for both shear and bond are important in reinforced concrete structures. Adequate shear resistance in reinforced concrete members is essential to prevent shear failures which are brittle in nature. The performance of reinforced concrete structures depends on sufficient bond between concrete and reinforcing steel. The present research therefore focuses on the shear and bond behaviour of reinforced low calcium fly ash-based geopolymer concrete beams. / For the study of shear behaviour of geopolymer concrete beams, a total of nine beam specimens were cast. The beams were 200 mm x 300 mm in cross section with an effective length of 1680 mm. The longitudinal tensile reinforcement ratios were 1.74%, 2.32% and 3.14%. The behaviour of reinforced geopolymer concrete beams failing in shear, including the failure modes and crack patterns, were found to be similar to those observed in reinforced Portland cement concrete beams. Good correlation of test-to-prediction value was obtained using VecTor2 Program incorporating the Disturbed Stress Field Model proposed by Vecchio (2000). An average test-to-prediction ratio of 1.08 and a coefficient of variation of 8.3% were obtained using this model. It was also found that the methods of calculations, including code provisions, used in the case of reinforced Portland cement concrete beams are applicable for predicting the shear strength of reinforced geopolymer concrete beams. / For the study of bond behaviour of geopolymer concrete beams, the experimental program included manufacturing and testing twelve tensile lap-spliced beam specimens. No transverse reinforcement was provided in the splice region. The beams were 200 mm wide, 300 mm deep and 2500 mm long. The effect of concrete cover, bar diameter, splice length and concrete compressive strength on bond strength were studied. The failure mode and crack patterns observed for reinforced geopolymer concrete beams were similar to those reported in the literature for reinforced Portland cement beams. The bond strength of geopolymer concrete was observed to be closely related to the tensile strength of geopolymer concrete. Good correlation of test bond strength with predictions from the analytical model proposed by Canbay and Frosch (2005) were obtained when using the actual tensile strength of geopolymer concrete. The average ratio of test bond strength to predicted bond strength was 1.0 with a coefficient of variation of 15.21%. It was found that the design provision and analytical models used for predicting bond strength of lapsplices in reinforced Portland cement concrete are applicable to reinforced geopolymer concrete beams.

Made available in DSpace on 2014-12-17T14:57:40Z (GMT). No. of bitstreams: 1 SaniaMBAF.pdf: 3070934 bytes, checksum: 722dda15cd04d9eb4986b09211186f20 (MD5) Previous issue date: 2008-06-05 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Geopolymers are cementing materials that depict a number of advantages compared to Portland cement. Contrary to the latter, geopolymers are synthesized at room temperature, thus significantly reducing the emission of CO2 to the atmosphere. Moreover, the composition and synthesis reactions can be tailored to adjust the setting time of the material as well as its compressive mechanical strength. It is then possible to produce geopolymeric cements with short setting times and high compressive strength, although relatively brittle. The objective of the present study was to produce and characterize composite materials by reinforcing fastsetting geopolymeric matrixes with polypropylene geosynthetics (geomats and geotextiles) in an attempt to improve the toughness and tensile strength of the cementing material. Geosynthetics have been increasingly used to reinforce engineering structures, providing higher strength and better toughness. In particular, polypropylene nonwoven and geomats depict other attractive properties such as low density, durability, impact absorption and resistance to abrasion. Fast-setting geopolymers were then synthesized and reinforced with polypropylene nonwoven and geomats. The mechanical strength of the materials, reinforced or not, was characterized. The results showed that relatively short setting times and adequate flowing behavior were achieved by adjusting the composition of the geopolymer. In addition, it is possible to improve the fracture resistance of geopolymeric cements by adding polypropylene geosynthetics. The best results were achieved by reinforcing geopolymer with polypropylene TNT / Geopol?meros s?o materiais cimentantes que apresentam uma s?rie de vantagens quando comparados ao cimento Portland. Ao contr?rio deste, a s?ntese de geopol?meros ? feita em temperaturas pr?ximas da ambiente, reduzindo significativamente a emiss?o de CO2 para a atmosfera. Al?m disso, tanto a composi??o quanto ?s condi??es das rea??es de s?ntese podem ser ajustadas para que os materiais resultantes tenham o tempo de pega e as propriedades mec?nicas desejadas. Desta forma, ? poss?vel produzir geopol?meros de pega r?pida e com resist?ncias mec?nicas relativamente altas, embora seu comportamento seja intrinsecamente fr?gil. Nesse contexto, o objetivo do presente trabalho foi estudar a produ??o e as propriedades de comp?sitos produzidos a partir do refor?o de matrizes geopolim?ricas com polipropileno, a fim de reduzir o car?ter fr?gil dos materiais. Para esta finalidade foram empregados geosint?ticos (geot?xteis e geomanta) de polipropileno. Esses materiais t?m sido amplamente utilizados com refor?o estrutural, proporcionando maiores resist?ncias ? tra??o e tenacidade. Em particular, tecidos n?o tecidos e geomantas de polipropileno apresentam outras propriedades atraentes como baixa densidade, durabilidade, absor??o ao impacto e resist?ncia ? abras?o. Geopol?meros de pega r?pida foram sintetizados e refor?ados com tecido n?o tecido e geomanta de polipropileno. A resist?ncia mec?nica dos geopol?meros, com e sem refor?o, foi avaliada. Os resultados mostraram que o ajuste na formula??o do geopol?mero permitiu produzir pastas com tempos de pega relativamente curtos e ao mesmo tempo, mant?-las com a fluidez necess?ria para o recebimento do refor?o. Comprovou-se que a presen?a de geosint?ticos aumentou a energia de fratura do geopol?mero, sendo que os melhores resultados foram alcan?ados com refor?o de TNT

Abstract Biomass, such as wood, binds CO2 as it grows, and is thus considered an environmentally friendly alternative fuel to replace coal. In Finland, biomass is typically co-combusted with peat, and also municipal waste is becoming more common as a fuel for power plants. Wood, peat and waste-based fuels are typically burned in fluidized bed combustion (FBC) boilers. Ash is the inorganic, incombustible residue resulting from combustion. The annual production of biomass and peat ash in Finland is 600 000 tonnes, and this amount is likely to increase in the future, since the use of coal for energy production will be discontinued during the 2020s. Unfortunately, FBC ash is still largely unutilized at the moment and is mainly dumped in landfills. The general aim of this thesis was to generate information which could potentially improve the utilization of FBC ash by alkali activation. The specific objective was to produce geopolymer aggregates by means of a simultaneous alkali activation-granulation process. It was shown that geopolymer aggregates with physical properties comparable to commercial lightweight expanded clay aggregates (LECAs) can be produced from FBC fly ash containing heavy metals. Although the ashes were largely unreactive and no new crystalline phases were formed by alkali activation, a new amorphous phase was observed in the XRD patterns, possibly representing micron-sized calcium aluminate silicate hydrate-type gels. The heavy metal immobilization efficiency of alkali activation varied with the type of fly ash. Good stabilization was generally obtained for cationic metals such as Ba, Pb and Zn, but in common with the results obtained with alkali activation of coal fly ash, anionic metals became leachable after alkali activation. The efficiency of immobilization depended on the physical and chemical properties of the fly ash and was not related to the total content of the element. All the geopolymer aggregates met the criteria for a lightweight aggregate (LWA) as defined by EN standard 13055-1. Their strength depended on the reactivity and particle size distribution of the fly ash. Mortars and concretes prepared with such geopolymer aggregates had higher mechanical strength, higher dynamic modulus of elasticity and higher density than concrete produced with commercial LECA, while exhibiting similar rheology and workability. / Tiivistelmä Biopolttoaineet, esimerkiksi puu, ovat ympäristöystävällinen vaihtoehto kivihiilelle, koska ne sitovat hiilidioksidia kasvaessaan. Suomessa biopolttoaineita poltetaan tyypillisesti turpeen kanssa, ja nykyään myös jätteen hyödyntäminen polttoaineena on yleistynyt. Puu, turve ja jätepolttoaineet poltetaan tyypillisesti leijupetipoltto-tekniikalla. Tuhka on polton epäorgaaninen, palamaton jäännös. Puun ja turpeen tuhkaa tuotetaan Suomessa 600 000 tonnia vuodessa ja määrän odotetaan kasvavan, sillä kivihiilen poltto lopetetaan 2020-luvulla. Leijupetipolton tuhkaa ei tällä hetkellä juurikaan hyödynnetä ja tuhka päätyykin pääasiassa kaatopaikoille. Tämän tutkielman päämääränä oli tuottaa tietoa, joka parantaisi leijupetipolton tuhkien hyödyntämistä alkali-aktivaatiolla. Erityisesti tavoitteena oli valmistaa geopolymeeriaggregaatteja yhtäaikaisella alkali-aktivaatiolla ja rakeistuksella. Tutkielmassa osoitettiin, että raskasmetalleja sisältävistä tuhkista valmistettujen geopolymeeriaggregaattien fysikaaliset ominaisuudet ovat vertailukelpoiset kaupallisten kevytsora-aggregaattien (LECA) kanssa. Vaikka tuhkien reaktiivisuus oli matala, ja uusia kidefaaseja ei muodostunut alkaliaktivaatiolla, uusi amorfinen faasi havaittiin XRD-mittauksissa. Uusi amorfinen faasi oli mahdollisesti mikrometrikokoluokan kalsium-aluminaatti-silikaatti-hydraatti-tyyppinen rakenne. Raskasmetallien stabiloinnin tehokkuus vaihteli tuhkien välillä. Kationiset metallit, kuten barium, lyijy ja sinkki, stabiloituivat pääasiassa hyvin, mutta anionisten metallin liukoisuus kasvoi alkali-aktivoinnin myötä. Stabiloinnin tehokkuus riippui tuhkien fysikaalisista ja kemiallisista ominaisuuksista, mutta raskasmetallin kokonaispitoisuudella ei ollu vaikutusta. Kaikki geopolymeeriaggregaatit olivat kevytsora-aggregaatteja standardin EN 13055-1 mukaisesti. Aggregaattien lujuus riippui tuhkan reaktiivisuudesta ja partikkelikokojakaumasta. Geopolymeeriaggregaateilla valmistettujen laastien ja betonien mekaaninen lujuus, Youngin moduuli ja tiheys olivat korkeampia kuin kaupallisella kevytsora-aggregaateilla valmistetut, vaikka niiden reologia ja työstettävyys olivat samanlaisia.

Il est communément admis que les géopolymères sont des solutions potentielles comme alternative aux liants hydrauliques classiques. Les géopolymères sont produits à partir de réactifs non carbonés contrairement au ciment portland et nécessitent relativement peu d'énergie pour être élaborés. Ce sont des liants inorganiques issus de l'activation alcaline d'aluminosilicates. Afin de faire des géopolymères une alternative viable et industriellement intéressante, plusieurs verrous technologiques doivent être levés en particulier sur leur mise en œuvre et les mécanismes chimiques impliqués au très jeune âge. Les études précédentes sur les mécanismes de cette réaction de géopolymérisation montrent l'existence d'un mécanisme en trois phases (dissolution – réorganisation – polymérisation). Notre étude s'est portée sur les mécanismes impliqués dans le comportement à l'état frais et en prise de géopolymère modèle à base de métakaolin. Pour cela, nous avons développé une approche combinée entre les mesures rhéologiques et chimiques (RMN liquide) afin de répondre à la complexité de l'hétérogénéité chimique locale pendant la géopolymérisation. Dans les deux premières parties de la thèse, nous nous sommes intéressés à comprendre le développement des propriétés mécaniques du gâchage à la prise du géopolymère. Lors de mesures de suivi de module élastique au cours du temps, nous observons également trois phases, une première augmentation de module dès les premières centaines de secondes, un plateau caractéristique d'une période de latence puis une seconde augmentation de module après plusieurs heures. Dans un premier temps, nous sommes intéressés à la première augmentation de module. Il a été établi que l'origine de ce module était la formation d'un premier gel de rapport Si/Al < à 4.5 localisé au niveau des joints de grains de métakaolin. Dans un second temps, nous sommes focalisé sur la dernière augmentation de module dont l'origine est la formation d'un second gel dont la composition chimique est celle du produit final c'est-à-dire le géopolymère de rapport Si/Al ~2.Finalement, dans une troisième partie, nous avons mis évidence les principales différences qui existent entre les géopolymères et de ciment Portland d'un point de vue rhéologique. Ces matériaux se comportent comme des fluides newtoniens. Les interactions entre les particules sont dominées par les effets hydrodynamiques, qui sont principalement contrôlés par la viscosité élevée de la solution alcaline de silicate et non par la contribution des contacts directs entre les grains de métakaolin / It is commonly accepted that the geopolymers are potential solutions as an alternative to conventional hydraulic binders. Geopolymers are produced from no-carbon reactants unlike Portland cement and require relatively little energy to be developed. These are inorganic binders from the alkali activation of aluminosilicates. To make a geopolymer as viable alternative and industrially interesting, several technological hurdles must be overcome in particular, their casting and the chemical mechanisms involved at very early age. Previous studies on the mechanisms of this reaction of geopolymerisation show the existence of a three phase's mechanism (dissolution - reorganization - polymerization). Our study focused on the mechanisms involved in fresh behavior and during setting of model metakaolin based geopolymers. For this, we have developed a combined approach between the rheological measurements and chemical measurements (liquid NMR) to respond to the complexity of the local chemical heterogeneity during geopolymerisation. In the first two parts of the thesis, we are interested in understanding the development of mechanical properties from mixing to setting of geopolymers. During the measurement of the elastic modulus' evolution, we also observe three phases, the first increase of elastic modulus during the first few hundred seconds, a plateau characteristic of a latency period followed by a second increase of elastic modulus after several hours. As a first step, we are interested in the first increase of modulus. It was established that the origin of this modulus was the formation of a first gel with a Si / Al ratio <4.5 localized at the grain boundaries of metakaolin. In a second step, we focused on the last increase of the elastic modulus. The origin is the formation of a second gel; the chemical composition is that of the final product that is to say the geopolymer with a Si / Al ratio ~ 2.Finally, in the third part, we have identified the major differences between geopolymer and Portland cement from a rheological point of view. These materials behave as Newtonian fluids. The interactions between the particles are dominated by hydrodynamic effects, which are mainly controlled by the high viscosity of the alkaline silicate solution and not the contribution of direct contacts between the grains of metakaolin

Ce travail s’inscrit dans le cadre de l’étude de liants aluminosilicatés que sont les géopolymères. La première partie de ce travail a consisté à caractériser la texture poreuse des géopolymères, par des techniques intrusives (porosimétrie à eau, adsorption-désorption d’azote, intrusion mercure) et non-intrusives (diffusion des rayons X et des neutrons aux petits angles). Le terme « texture poreuse » regroupe la forme et la taille des pores, le volume poreux, la surface spécifique et la connectivité des pores. En parallèle, l’évolution de la texture poreuse et des propriétés mécaniques a été suivie sur une période de deux ans, en évitant les échanges avec le milieu extérieur afin d’étudier l’évolution intrinsèque des géopolymères. La seconde étape a consisté à étudier les propriétés thermodynamiques, la structure et la dynamique de l’eau confinée dans la porosité, par calorimétrie différentielle à balayage basse température, par diffusion des neutrons et par des essais de migration. La structure poreuse des géopolymères est complexe, puisqu’il s’agit d’une porosité multi échelle, méso- et macroporeuse, essentiellement ouverte et connectée. Elle consiste en un réseau vermiculaire de mésopores et un réseau de macropores connecté via les mésopores. La taille caractéristique (comprise entre 4 et 10 nm environ) et le volume des mésopores dépendent de la formulation de la pâte de géopolymère, à savoir de la teneur en eau, du rapport molaire Si/Al et de la nature du cation compensateur de charge. Il a été montré que les géopolymères étudiés sont très poreux, la porosité représentant entre 40 et 50 % du volume total du matériau. Le volume mésoporeux représente entre 7 et 15 % du volume total, le reste étant attribué à un volume macroporeux. Au cours du temps, la porosité des géopolymères se ferme légèrement, ceci étant attribué à un mécanisme de dissolution-reprécipitation au niveau des murs de pores. Les propriétés mécaniques atteignent un maximum entre 7 et 10 jours, puis sont stables dans le temps lorsque les échantillons sont conservés à 20°C et à l’abri du séchage ou de la carbonatation de la solution porale. Par ailleurs, trois types d’eau ont été mises en évidence au sein des pores : (i) l’eau liée chimiquement et/physiquement à la surface des parois, (ii) l’eau libre confinée dans les mésopores, et (iii) l’eau libre dans les macropores. A l’échelle locale, les molécules d’eau possède une mobilité proche de celle de l’eau libre, tandis qu’à l’échelle macroscopique, une diminution d’un ordre de grandeur du coefficient de diffusion a été observé, avec un effet probable de la taille des mésopores. / In this study, we have investigated the porous network of geopolymers. The first step consisted in characterizing the structure of the porous network by the means of both intrusive experimental techniques (water porosimetry, gas sorption and mercury intrusion) and non-intrusive techniques (small-angle X-ray and neutron scattering). By the same time, the evolutions of the porous structure as well as the mechanical properties were followed over time. The second step was to determine the structure, the thermodynamics and the dynamics of water confined in the porosity by differential scanning calorimetry, quasi-elastic neutron scattering and migration tests.Geopolymer pore structure is a complex multi-scale porosity, a meso- and macroporous network, essentially open and connected. It consists in a vermicular mesoporous network which connects the macropores. The mesopore characteristic size depends on the formulation of the geopolymer paste and is ranged between about 4 and 10 nm. Geopolymer have a total pore volume comprised between 40 and 50 %, the mesoporous volume represents between 7 and 15 % of the material global volume. The majority of the pore volume is then attributed to macropores. A slight closure of porosity was observed with time and was attributed to a dissolution-precipitation mechanism occurring at pore wall interfaces. The mechanical properties reach a maximum within 10 days, and then are stable over time when the samples were kept from drying and carbonation and at the temperature of 20°C. Besides, three kinds of water were highlighted inside the porosity: (i) an interfacial water linked at the pore surfaces, (ii) free water inside the mésopores and (iii) free water inside macropores. At local time scale, the mobility of water was found close to the one of free water, and at the macroscopic scale, a decrease in diffusion coefficient of one order of magnitude was observed, together with an effect of mesopore size.

This master´s thesis deals with the suppression of the growing of algae in cooling towers. Subject of the work is suggestion and testing surface modification of the existing mature concrete in order to suppress the growth of algae. In the frame surface modification, several commercially available and newly developed systems were tested. Testing systems are based on the basis of portland cement, geopolymers or formation of insoluble complex compounds containing metal elements (Zn, Cu). Experimental methods were applied in the real environment of cooling towers of Dukovany Nuclear power plant.