O silicato de cálcio hidratado (C-S-H) é o componente responsável pela resistência mecânica dos cimentos usados na construção civil. Neste trabalho foi caracterizada a evolução da reação de hidratação e as propriedades estruturais das fases resultantes da hidratação da escória de alto forno granulada (EAF). Este tipo de cimento é um potencial candidato para substituir os materiais convencionais, apresentando vantagens relativas ao menor custo energético de produção e a redução do impacto ambiental. Devido à menor reatividade da EAF com água, é necessário a adição de substâncias ativadoras alcalinas de modo geral em baixa concentração. Neste trabalho foi caracterizado o efeito sobre a sua reatividade e as propriedades estruturais dos produtos da reação (C-S-H e aluminatos de cálcio hidratados) de quatro tipos de misturas ativadoras contendo hidróxido de sódio, silicato de sódio e/ou hidróxido de cálcio (CH). As quantidades alcalinas resultantes das misturas usadas nas pastas foram: 5%Na2O, 5% Na2O-2,5%CH, 5% Na2O -7,5%SiO2 e 5% Na2O -2,5%CH- 7,5% SiO2. A técnica experimental utilizada foi a Ressonância Magnética Nuclear (RMN) de alta resolução no estado sólido de 29Si, 27Al e 23Na. Os resultados indicaram diferenças na cinética da reação no estágio tardio (tempos na faixa de 3 dias até 120 dias), na quantidade e nas características estruturais das fases aluminatos de cálcio e do C-S-H, dependentes da presença de SiO2 na mistura ativadora. A inclusão de Ca(OH)2 tem efeitos de magnitude consideravelmente menor sobre estes parâmetros. Foi observada uma correspondência excelente entre as diferenças estruturais observadas por RMN e o comportamento da resistência mecânica do material. / Calcium Silicate Hydrate (C-S-H) is the component responsible for mechanical resistance of cementitious materials. In this work, a characterization of the evolution of the hydration reaction in granulated blast-furnace slag (bfs) is presented. Also, the structural properties of the reaction products is studied as a function of time, during the late period of the process. This kind of cement is a potential material to replace the conventional Portland in several applications, having several relative advantages regarding to energetic cost and impact on the environment. To overcome the less hydraulic reactivity of gbs respect to Portland, it is generally necessary the addition of small amount of alkaline compounds, called activators, to improve the speed and extension of the reaction. The behavior of four different activator mixtures containing sodium hydroxide, sodium silicate and/or calcium hydroxide (CH) were considered, at fixed amount alkali 5% Na2O, 5% Na2O -2,5% Ca(OH)2, 5% Na2O -7,5% SiO2 and Na2O -2,5% Ca(OH)2- 7,5% SiO2. The hydration kinetics and structural properties of the hydration products, C-S-H and calcium aluminate hydrates, were probed by means of solid-state high resolution Nuclear Magnetic Resonance (NMR) of 29Si, 27Al and 23Na nuclei. Results showed differences in hydration evolution and structural properties depending strongly on the presence of SiO2 in the mixture. On the other hand, Ca(OH)2 produced only marginal effects on the reaction. An excellent correlation was observed between the structural differences and the mechanical response of the material as a function of the hydration time.

Une solution pour réduire l’impact environnemental du béton est de substituer une partie du ciment par des additions minérales, comme le laitier de hauts fourneaux. Néanmoins, cette substitution ne doit pas réduire les performances du matériau vis-à-vis de la carbonatation, l’un des principaux phénomènes de vieillissement des structures en béton armé. La carbonatation est une réaction chimique entre la matrice cimentaire et le dioxyde de carbone présent dans l’air. Cette réaction, en plus de former du carbonate de calcium, diminue le pH de la solution interstitielle rendant ainsi les armatures vulnérables à la corrosion. Les essais accélérés de carbonatation montrent, en laboratoire, une grande disparité de comportements entre matériaux cimentaires très faiblement poreux à hautes performances mécaniques et matériaux plus poreux en usage dans les ouvrages courants. L’objectif de cette thèse est de mieux comprendre le phénomène de carbonatation des matériaux cimentaires, notamment ceux contenant du laitier de hauts-fourneaux. Nous avons procédé en découplant les phénomènes impliqués dans la carbonatation que sont la diffusion gazeuse, les réactions chimiques et les transferts hydriques (séchage). La première partie de ces travaux de thèse a nécessité le développement et la validation d’un dispositif de mesure expérimental du coefficient de diffusion du CO2. Ce dernier a permis une étude paramétrique sur pâtes mettant en évidence l’influence de la composition et de la carbonatation sur la diffusion. La seconde partie a porté sur l’étude des cinétiques de carbonatation de pâtes en fonction du degré de saturation, après une mise à l’équilibre hydrique sur une longue période. Ces cinétiques ont été étudiées, sur échantillons de faibles dimensions, au moyen d’un suivi des évolutions pondérales et d’analyses thermogravimétriques, pour l’identification des hydrates résiduels et des carbonates formés. Nous avons ainsi mis en évidence des différences de comportement des hydrates et des liants vis-à-vis de la carbonatation impliquant la microstructure du matériau. / One solution for reducing the environmental impact of concrete is to substitute a part of cement by mineral additions, such as granulated blast furnace slag. However, this substitution should not reduce the performances of concrete with respect to carbonation, one of the main ageing phenomena of reinforced concrete structures. Carbonation is a chemical reaction between the cement matrix and the carbon dioxide from the atmosphere. In addition to the formation of calcium carbonate, this reaction results in a pH reduction of the pore solution and a risk of corrosion. Laboratory accelerated tests show a wide disparity between the carbonation resistance of high mechanical performances concretes with low porosity and the resistance of more porous and more usual ones. The objective of this thesis is to better understand the phenomenon of carbonation of cementitious materials, including those containing blast furnace slags. This work was carried out by decoupling the phenomena involved in carbonation that are gaseous diffusion, chemical reactions and water transfers. First, an experimental device for measuring the CO2 diffusion coefficient was developed. After validation, the latter was used in a parametric study carried out on cement pastes showing the influence of composition and carbonation on the diffusion coefficient. The second part of the thesis work focused on studying the kinetics of carbonation of pastes with respect to the degree of water saturation. Prior to carbonation, the studied pastes were conserved during a long period at various RH to achieve hydric equilibrium. The carbonation kinetics of small size samples of pastes was studied by means of monitoring of weight changes and thermogravimetric analyzes for identification of residual hydrates and formed carbonates. We have thus shown differences in behavior of hydrates and binders during carbonation involving the material microstructure.

O uso de escória de alto forno como aglomerante alternativo ao cimento portland tem sido objeto de vários estudos no Brasil e no exterior. Além de representar vantagens ao meio ambiente por ser um resíduo, a escória apresenta boas possibilidades de emprego, principalmente pelo baixo custo e por suas vantagens técnicas das quais se destacam a elevada resistência mecânica, a boa durabilidade em meios agressivos, o baixo calor de hidratação. No entanto, o emprego deste material carece de estudos detalhados da retração, muito superior à do cimento portland. Este trabalho teve como objetivo estudar a cinética das retrações autógena e por secagem não restringidas do cimento de escória ativada em função, principalmente, do tipo e teor de ativadores empregados. Para a retração autógena, o corpo-de-prova foi selado com papel alumínio protegido internamente com plástico. As medidas estenderam-se de 6 horas até 112 dias. O fenômeno da retração também foi analisado com base nos resultados dos ensaios de porosimetria, calorimetria, termogravimetria e difração de raios X. Foram empregados como ativadores: silicato de sódio, cal hidratada + gipsita, cal hidratada e hidróxido de sódio. Como referência foi adotado o cimento portland da alta resistência inicial CPV-ARI. De acordo com os resultados obtidos, a ativação da escória com silicato de sódio apresentou retração por secagem e autógena superior à apresentada pelos demais ativadores e pelo cimento portland. A maior parte dessa retração medida ocorre até os 7 dias. A retração por secagem ocorre em dois estágios: o primeiro logo após a desmoldagem e o segundo a partir do início da formação dos produtos hidratados. O início da retração autógena coincide com o segundo estágio da retração por secagem. Com base nos ensaios de microestrutura, são determinantes para a elevada retração do cimento de escória ativada com silicato de sódio: a baixa porosidade, caracterizada pela predominância quase total de mesoporos; o elevado grau de hidratação e natureza dos produtos hidratados, com predominância quase total de silicato cálcio hidratado (C-S-H). Na ativação com cal e com cal mais gipsita, a composição diferente dos produtos hidratados (baixa formação de C-S-H e presença significativa de fases aluminato e sulfoluminato, respectivamente) altera a porosidade e a retração, principalmente a autógena que apresenta valores inferiores à do cimento portland. A ativação com hidróxido sódio é caracterizada pela elevada retração autógena e baixa formação de C-S-H, com presença significativa de fases aluminato. / The use of ground granulated blast furnace slag (BFS) as an alternative binder to portland cement has been the subject of numerous studies in Brazil and other countries. Because BFS is a residue, its use benefits the environment. Furthermore, BFS cement is less costly and shows technical advantages if compared with normal portland cement, namely the higher strength, good durability in aggressive environments, and low heat of hydration. On the other hand, the high shrinkage of BSF cement is often indicated as one of the major limiting aspects for its use. The objective of this research was to study the development of unrestrained autogenous and drying shrinkage of BSF cement as function, mainly, of the chemical activator types and dosages. Autogenous shrinkage was measured in fully aluminum foil and plastic sheet wrapped specimens. Measurements were taken from 6 hours up to 112 days. Shrinkage was also analyzed in conjunction with mercury posorimetry, conduction calorimetry, thermogravimetric analysis and X-ray diffraction tests. Activators used were sodium silicate, hydrated lime + gypsite, hydrated lime and sodium hydroxide. High early strength portland cement was used as reference. The results showed that autogenous and drying shrinkage were larger when BFS was activated with sodium silicate. Most of the shrinkage occurs before 7 days of hydration. Drying shrinkage occurs in two phases: the first phase immediately after demolding, and the second phase concurrently with the formation of the hydrated products. Autogenous shrinkage coincides with the second phase of the drying shrinkage. Based on microstructure analysis, determining factors could be identified that respond for the high shrinkage of sodium silicate activated BFS cement: low porosity, mostly mesopores; high degree of hydration and chemical nature of the hydrated products, essentially calcium silicate hydrate - C-S-H. Activation with hydrated lime and hydrated lime plus dehydrated calcium results low amounts of C-S-H and significant quantities of aluminate and sulphoaluminate phases, respectively. Porosity and shrinkage, mainly autogenous, are lower than that verified for portland cement mixtures. Activation with sodium hydroxide causes high autogenous shrinkage, small amounts of C-S-H and significant quantities of aluminate phases.

The influence of supplementary materials such as slag, metakaolin and limestone in steam-cured ternary and quaternary cement blends on physical and chemical hydration mechanisms was studied by analyzing the evolution of non-evaporable water content, hydration products and compressive strength. The role of limestone in hydration reactions of cement was also investigated. These properties were studied through the use of differential thermal and thermogravimetric analyses, as well as the loss-on-ignition, X-ray diffraction and compressive strength tests at 1, 3, 7, and 28 days. Research findings revealed that it is possible to replace up to 40% cement with other materials and still achieve compressive strengths similar to mixtures with a 25% cement replacement at 0.34 w/b ratio. Additionally, ternary limestone mixtures exhibited superior mechanical properties to ternary metakaolin mixtures. Lastly, limestone powder was determined to behave as inert filler, accelerating hydration at early ages through heterogeneous nucleation.

The influence of supplementary materials such as slag, metakaolin and limestone in steam-cured ternary and quaternary cement blends on physical and chemical hydration mechanisms was studied by analyzing the evolution of non-evaporable water content, hydration products and compressive strength. The role of limestone in hydration reactions of cement was also investigated. These properties were studied through the use of differential thermal and thermogravimetric analyses, as well as the loss-on-ignition, X-ray diffraction and compressive strength tests at 1, 3, 7, and 28 days. Research findings revealed that it is possible to replace up to 40% cement with other materials and still achieve compressive strengths similar to mixtures with a 25% cement replacement at 0.34 w/b ratio. Additionally, ternary limestone mixtures exhibited superior mechanical properties to ternary metakaolin mixtures. Lastly, limestone powder was determined to behave as inert filler, accelerating hydration at early ages through heterogeneous nucleation.

Four different kinds of filter-materials with reactive surfaces have been studied concerning their capacity to absorb heavy metals in leachate from a municipal waste deposit. The heavy metals studied were: lead, cadmium, copper, mercury, chromium, nickel and zinc. The leachate contains high levels of dissolved organic carbon (DOC) and has a high pH-value along with a high buffer capacity. These characteristics of the leachate make it difficult to remove pollutants and require efficient filters. The filters that were examined in the report are blast-furnace slag with CaO, sand covered with iron oxides, olivine and nepheline. The experiment was carried out in two sets, starting with batch experiments followed by a column study. The objective of the batch experiments was to find out how variations in pH affected the sorption capacity of the materials. The interval used during the test was from pH 5 to pH 10. The computer program VisualMinteq was used to evaluate the dominating sorption processes when the materials interacted with the solutions. Two different kinds of solutions were used in the batch experiment. One of them was the leachate, to which known concentrations of heavy metals were added (about 1 μM) and the other consisted of sodium nitrate, a solution without organic compounds, which was used as a reference. The sodium nitrate solution was also spiked with the same concentration of heavy metals as the leachate. The results from the batch experiment showed that the sorption of heavy metals was lowered if the DOC level was high. No relation between pH and sorption ability could be found for the leachate, but for some metals in the sodium solution a higher pH improved the removal of heavy metals. The two materials that showed best results in the batch experiment were the blast-furnace slag and the sand with iron oxides. These materials were used in the column study. The olivine material was somewhat better than the nepheline in the batch experiment. Four columns were used in the column study, two for each material. Leachate with heavy metals was pumped into the columns with a specific flow rate; at first a low flow rate was used and when half the experiment time had passed the flow rate was increased. The flow rates used were 0.12 m/24 h and 0.62 m/24 h. The outcome of the column experiment showed that the slag had the highest ability to adsorb metals. The metal sorption was over 60 percent for lead, cadmium and zinc, where the highest sorption was obtained for lead. No affects were noticed when the flow rate was increased. / I detta examensarbete har fyra olika reaktiva filtermaterials kapaciteter att ur deponilakvatten avskilja tungmetallerna bly, kadmium, koppar, kvicksilver, krom, nickel och zink testats. Deponilakvatten är ett avloppsvatten med höga halter organiskt material (DOC), högt pH och en hög buffertkapacitet. Dess sammansättning ställer stora krav på ett filter och närvaron av ligander påverkar sorptionprocesserna. Filtren som ingått i studien är kalciumoxiddopad masugnsslagg, järnoxidtäckt sand, olivin och nefelin. Försöken utfördes i två delar, med inledande skakförsök och därefter kolonnförsök. I båda försöken användes lakvatten med en extra tillsats av tungmetaller. I skakförsöken användes även natriumnitrat; ett referensvatten utan organiska ligander, även det spikat med tungmetaller. I skakförsöken studerades avskiljningens pH-beroende för de olika filtren, med ett pH-intervall på ca 5 – 10. Därefter modellerades resultaten i jämviktsprogrammet VisualMinteq för att fastställa vilka processer som styr avskiljningen. Skakförsöken och kolonnförsöken utfördes båda i klimatrum vid 8 ºC, för att efterlikna markens naturliga temperatur. Resultaten från skakförsöken visade att masugnsslagg och järnoxidsand gav bäst avskiljning för de flesta tungmetaller. Olivin och nefelin var sämre metallsorbenter, där olivin uppvisade något bättre resultat än nefelin. Inget tydligt pH-beroende för lakvattnet kunde utläsas, men för natriumnitratlösningen gav en pH-höjning en ökad sorption för vissa metaller. Den kemiska jämviktsmodelleringen visade att den dominerande processen i filtermaterialen var sorption på filterytorna. De två filtermaterialen som visade bäst resultat i skakförsöken (slagg och järnoxid) studerades vidare i kolonnförsök, där ett bestämt lakvattenflöde pumpades genom kolonner packade med materialen. Två olika flödeshastigheter testades (0,12 m/dygn och 0,62 m/dygn) och sorptionen av metaller analyserades. Slaggen uppvisade högst avskiljningskapacitet av de studerade filtren. De metaller som sorberades bäst var bly, kadmium och zink (över 60 % avskiljning), där den högsta sorptionen erhölls för bly. Gemensamt för både skak- och kolonnförsöken var att sorptionen försvårades då halten organiskt material (DOC) ökade, vilket beror på att DOC konkurrerar med de reaktiva ytorna på filtren om att binda den fria metalljonen. Ingen minskande avskiljningseffekt av en flödesökning kunde utläsas.

An excessive input of nutrients to lakes and other water bodies has created a problem with eutrophication in Sweden. Untreated, or partially treated, domestic sewage is a major source for discharge of phosphorus (P), which is the nutrient most frequently responsible for eutrophication of most fresh waters and the Baltic Sea. The waste water can be cleaned by filter materials, which have a high P-retention ability and which after saturation may be used as fertilizers. Four potentially suitable filter materials were tested in batch- and column experiments in this study. In the batch experiments, the following materials were shaken with waste water in time series ranging from 5 seconds to 60 minutes: coarse (1-4 mm) and fine (0-2 mm) Polonite® (heated bedrock from Poland); Filtralite® (light expanded clay aggregates with limestone added before burning); water cooled blast furnace slag (BF-slag) and BF-slag mixed with 10% burned limestone. In the column experiment, the phosphorus sorption capacity in BF-slag and BF-slag mixed with burned limestone was observed under saturated and unsaturated flow conditions for 10 weeks. The waste water used in both experiments originated from the full scale testing site at Ångersjön in Sweden. After the column experiment was ended, the filter materials were investigated with XRD (X-ray diffraction) and SEM (scanning electron microscope) in order to figure out which chemical reactions that had taken place. The results from the batch experiments show that fine Polonite® and BF-slag mixed with limestone have the fastest P sorption capacity. Already after 5 seconds of shaking the materials showed effective retention of P. The coarse Polonite®, Filtralite® and BF-slag showed similar sorption capacities, although the coarse Polonite® tended to be somewhat inferior. The column studies showed that the materials used in the columns had a sorption capacity of 98 % or more. The XRD and SEM indicated that an amorphous calcium-P-compound was created in the filter material. / I Sverige är reningen av fosfor i vatten från enskilda avlopp ofta bristfällig, vilket bland annat kan leda till övergödning av sjöar, hav och vattendrag. Sedan några år tillbaka har olika filtermaterial med speciella reaktiva egenskaper, som bland annat avskiljer fosfor från avloppsvatten, undersökts. Tanken med filtermaterialen är att de efter mättnad med näringsämnen ska kunnas användas som jordförbättringsmedel. I denna rapport har några olika filtermaterial, lämpade för fosforavskiljning, undersökts genom skak- och kolonnförsök. I skakförsök, där skaktiderna varierade mellan 5 sekunder och 60 minuter, testades Polonite®, Filtralite®, Hyttsand och Hyttsand blandad med 10 % bränd kalk. Polonite® är en upphettad form av bergarten opoka varav två olika kornstorleksfraktioner (0-2 mm och 1-4 mm) användes. Filtralite® och Hyttsand är antropogena filtermaterial. Filtralite® tillverkas i Norge och består av kalkhaltiga kulor av expanderad lera (Leca®). Hyttsand framställs genom vattenkylning av masugnsslagg som bildas vid framställningen av råjärn vid stålverket i Oxelösund. I kolonnförsöken, som utfördes under 10 veckor, studerades Hyttsand och Hyttsand blandad med 10 % bränd kalk under omättade och mättade flödesförhållanden. I samtliga experiment användes avloppsvatten från reningsverket vid Ångersjön, där Filtralite® och Hyttsand testas i fullskala. Efter kolonnförsöken avslutats undersöktes filtermaterialen med XRD (röntgendiffraktion) och SEM (svepelektron mikroskop) för att utreda vilka mekanismer som medverkat vid avskiljningen av fosfor. Resultaten från skakförsöken visade att finkornig Polonite® och Hyttsand blandad med kalk avskiljer fosfor effektivt redan efter skakning i 5 sekunder. Grovkornig Polonite, ren Hyttsand och Filtralite® sorberade fosfor tämligen likartat, även om den grovkorniga Poloniten® tenderade att vara aningen sämre än de övriga. Resultaten från kolonnförsöken visade att fosfor kunde avskiljas till över 98 % i alla kolonner och att det bildats amorfa fosfatföreningar, främst med kalcium, under den 2,5 månader långa experimentperioden.

Resíduos gerados em diversas indústrias têm sido aproveitados na produção de materiais buscando reduzir o impacto ambiental. No campo das fibras, materiais alternativos vem sendo produzidos em maior quantidade e ganhando destaque na fabricação de compósitos mais adequados ambientalmente. Entre estes produtos está a fibra de escória de alto-forno, microfibra cuja matéria-prima é originária da produção do ferro-gusa, que apresenta vantagens em seu processo produtivo citando-se custo reduzido e ganho ambiental ao proporcionar a ampliação da aplicabilidade de um subproduto gerado em elevada quantidade, tem despertado o interesse no seu uso como reforço de matrizes cimentícias. Neste sentido, a presente pesquisa visa avaliar se, além do beneficio ambiental proporcionado pela utilização da fibra de escória em substituição a outras fibras convencionais, a aplicação deste produto pode proporcionar também benefícios técnicos ao incrementar o desempenho de matrizes cimentícias. Para tanto o programa experimental foi dividido em quatro etapas, sendo a etapa inicial de caracterização dos materiais empregados e da fibra de escória por meio de ensaios de Fluorescência de Raios X, Difração de Raios X e Microscopia Eletrônica de Varredura (MEV). A segunda etapa foi proposta buscando avaliar a afinidade existente entre fibra e matriz cimentícia através do ensaio de Le Chatelier. Destinou-se a terceira parte do programa experimental ao preparo dos corpos-de-prova utilizados nos ensaios e a última para avaliação dos compósitos com relação à: Trabalhabilidade; Resistência à Tração na Flexão; Resistência à Compressão; Módulo de Elasticidade Dinâmico; Retração Restringida e Resistência ao Impacto. Os resultados não confirmaram a hipótese levantada, indicando que o desempenho da adição da fibra de escória em matrizes cimentícias foi insatisfatório, sendo constatada falha na distribuição da fibra através da produção de compósitos heterogêneos, com presença de aglomeração da fibra e incorporação de ar. Mesmo com o problema na dispersão da fibra, considerou-se com potencial promissor o resultado obtido no ensaio de retração restringida, onde foi possível verificar a atuação da microfibra de escória na distribuição das tensões permitindo o retardamento da fissuração nos anéis de argamassa reforçada. Estudos adicionais buscando melhorar a dispersão da fibra também não obtiveram bons resultados. Acredita-se que para fins de reforço em matrizes cimentícias a presença de resina adicionada à fibra de escória no seu processo de fabricação compromete a dispersão do material e, consequentemente, seu uso neste tipo de reforço. / Waste generated in various industries have been utilized in the production of materials seeking to reduce the environmental impact. In the field of fibers, alternative materials have been produced in greater quantity and gaining prominence in the manufacture of composites more environmentally appropriate. Among these products is of blast furnace slag fiber, microfiber whose raw material is sourced from the production of pig iron, which has advantages in its production process by citing the cost savings and environmental gains by providing expansion of the applicability of a byproduct generated in large amounts, has stimulated interest in its use as reinforcement in cementitious matrices. In this sense, this research aims to assess whether, in addition to environmental benefits provided by the use of slag fiber as a substitute for other conventional fibers, application of this product may also offer technical benefits to increase the performance of cementitious matrices. For both the experimental program was divided into four phases, the initial step of characterization of materials used and the slag fiber by tests of X-ray Fluorescence, X-ray diffraction and scanning electron microscopy (SEM). The second step was proposed by assessing the affinity between fiber and cement matrix by testing of Le Chatelier. Allocated to third part of the experimental program to prepare the bodies of the test piece used in the tests and the final assessment for the composites with respect to: Workability; Tensile strength in bending, compressive strength, dynamic modulus of elasticity; Restrained and Retraction Impact Resistance. The results did not confirm the hypothesis, indicating that the performance of slag addition of fiber in cementitious matrices was unsatisfactory, and found fault in the distribution of fiber through the production of composite heterogeneous with the presence of fiber clustering and incorporation of air. Even with the problem in dispersion of fiber, it was considered a promising potential with test result of restrained shrinkage, where it was possible to verify the performance of micro stress distribution in the slag allowing delayed cracking in mortar reinforced rings. Additional studies seeking to improve the dispersion of the fiber also did not obtain good results. It is believed that for purposes of reinforcement in cementitious matrices the presence of resin added to the slag fiber in its manufacturing process compromises the dispersal of the material and hence its use in this type of reinforcement.

The integrity of the rebars in reinforced concrete structures is related to the chemical and physical protection provided by the concrete layer that covers the steel. The destruction of the passivation layer precedes the onset of corrosion. Once the corrosion process starts, its rate of propagation will depend on the electrical resistivity between cathode and anode and the amount of oxygen available on the cathode. Concrete resistivity is a property linked both to the chemical and physical properties of the concrete. This study investigated the effect of the addition of blast furnace slag (BFS) on the electrical resistivity of concrete and correlated the effects of this addition on the concrete compressive strength as well as on changes in the chemical composition of aqueous phase and pore structure. Test specimens were prepared using different water/binder ratios (0.35, 0.50 and 0.65) and substitutions of 50 and 70% of BFS for cement by weight. A control sample (no BFS) was also prepared. Additionally, the effect of 4% sodium sulfate (Na2SO4) in samples with 50% BFS was also investigated. The electrical resistivity of concrete was determined using the fourelectrode method (Wenner s method adapted for use in concrete). Tests of compressive strength, porosimetry, electrical conductivity in the pore solution and the concentration of ions in the aqueous phase were performed. The tests showed there is an increase in the electrical resistivity of concrete as the degree of hydration and the concentration of BFS increase. This is related to the lower specific conductivity of the pore solution and the reduction in concrete pore size, which is shown by the good correlation between these two factors. The binary mixture with 50% BFS (50E) showed the best cost/benefit ratio for strength levels of 30MPa and 50MPa at 28 days and also for the strength level of 50MPa at 91 days. / A manutenção da integridade das armaduras nas estruturas de concreto é uma conseqüência da proteção física e química do concreto sobre o aço. A destruição da camada passivadora antecede o processo corrosivo. Uma vez iniciada a corrosão, a velocidade desta dependerá da resistividade elétrica existente entre o ânodo e o cátodo e também pela quantia de oxigênio presentes junto ao cátodo. A resistividade do concreto caracteriza-se por ser uma propriedade ligada tanto a características físicas como químicas do mesmo. Neste trabalho objetivou-se estudar o comportamento da adição de escória de alto forno na resistividade elétrica aparente dos concretos, assim como correlacionar com a resistência à compressão e as alterações químicas na fase aquosa bem como na estrutura dos poros. Foram realizadas investigações em misturas com relação a/agl 0,35, 0,50 e 0,65 com teores de substituição em massa de 0, 50 e 70% de EAF. Investigou-se também os efeitos produzidos pela incorporação de 4% de sulfato de sódio (Na2SO4) em misturas contendo 50% de EAF. A resistividade elétrica do concreto foi determinada utilizando o método dos quatro eletrodos (método de Wenner adaptado para uso em concreto). Foram também realizados ensaios de resistência à compressão axial, porosimetria, concentração de íons da fase aquosa e determinada a condutividade elétrica específica da solução dos poros. Constatou-se aumento na resistividade elétrica do concreto com o aumento no grau de hidratação e do teor de escória. Este comportamento está relacionado a menor condutividade elétrica específica da solução dos poros e ao refinamento dos poros comprovado pela boa correlação entre esses dois fatores. A mistura binária composta por 50% de escória (50E) apresentou a melhor relação custo/benefício para os níveis de resistência de 30MPa e 50MPa aos 28 dias e também para o nível de resistência de 50MPa aos 91 dias.

Made available in DSpace on 2014-06-11T19:24:42Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-06-18Bitstream added on 2014-06-13T18:52:30Z : No. of bitstreams: 1 leite_rm_me_botfca.pdf: 900205 bytes, checksum: b5ec7670608ceeed67a5807c39d81b4e (MD5) / A escória de siderurgia é um dos resíduos gerados durante a produção de ferro-gusa. O Brasil é um dos maiores produtores de ferro-gusa e isso significa geração de aproximadamente dez milhões de toneladas por ano deste passivo ambiental. Entretanto, as escórias básicas de siderurgia podem ser usadas como corretivos de acidez do solo, fornecendo cálcio, magnésio e silício, sendo que o seu uso evita a extração de outros produtos da natureza, como o calcário, por exemplo. Os objetivos deste trabalho foram avaliar a influência das escórias de siderurgia no crescimento e nutrição do eucalipto na sua fase inicial (6 meses pós plantio) e nos atributos químicos do solo. O experimento foi conduzido em Latossolo e Neossolo Quartzarênico e foi analisado de duas formas: 1ª) avaliação do efeito da aplicação de doses crescentes de escória (doses proporcionais a zero; 300; 600; 1200 e 2400 kg/ha); e 2ª) comparação do tratamento equivalente a 2400 kg/ha de escória com testemunha absoluta, adubação química (somente NPK) e calcário. O delineamento experimental foi o de blocos inteiramente casualizados, com seis repetições. Foram realizadas análises químicas de solo aos três e aos seis meses após o início da condução do experimento. Avaliou-se mensalmente a altura e o diâmetro das plantas e, ao encerramento, quantificou-se massa verde e massa seca de folhas, galhos, tronco e raízes, área foliar, teores de macro e micronutrientes e silício nas folhas, galhos, tronco e raízes. Os dados foram analisados estatisticamente com o auxílio do programa SISVAR.2 Os resultados indicaram que, após três meses, a aplicação de 2400 kg/ha de escória proporcionou aumento do pH e V% do solo e redução da acidez potencial em ambos os solos. Após seis meses do plantio, os valores de pH foram semelhantes quando se comparou a dose de 2400 kg/ha com o calcário... / Blast furnace slag is one of residues generated during cast-iron production. Brazil is one of the largest producers of cast-iron. This means the generation of approximately ten million tonnes per year of environmental liabilities. However, slag can be used as soil pH-correcting material supplying calcium, magnesium and silicon, and that its use prevents the extraction of other products of nature, such as limestone, for example. The objectives of this study were to evaluate the influence of blast furnace slags on growth and nutrition of eucalyptus in its initial phase (6 months after planting) and chemical soil attributes. The experiment was conducted in Oxisol and a Typic Quartzipsamment and was analyzed in two ways: 1st) evaluation of the effect of application of increasing slag doses (rates proportional to zero, 300, 600; 1200 and 2400 kg / ha), and 2nd) comparison of a treatment equivalent to 2400 kg / ha of slag against an absolute control, chemical fertilization (NPK only) and limestone. The experimental design consisted of completely randomized blocks with six repetitions. Soil chemical analyses were performed three and six months after installation of the experiment. It was evaluated monthly height and diameter of the plants and the closure, is quantified green and dry mass of leaves, branches, trunk and roots, leaf area; macronutrient, micronutrient, and silicon in the leaves, branches, trunk and roots . The data were analyzed statistically using the SISVAR software program. The results indicated that, after three months, the application of 2400 kg / ha of slag increased soil pH and V%, and decreased potential acidity in both soils. Six months after planting, pH values were similar when the 2,400 kg / ha dose was compared with the dose of limestone. Increased slag doses provided increased green and dry mass production of leaves, leaf area, and dry mass of branches, increased leaf... (Complete abstract click electronic acess below)