Essa dissertação analisa a construção da história e da memória da Fábrica de Ferro de São João de Ipanema, na região de Sorocaba, a partir do referencial teórico de R.G. Collingwood, o qual formulou a conhecida história de cola e tesoura, com o intuito de questionar escritas da história ou práticas historiográficas em que seus autores apenas trabalham de maneira acrítica com relatos já produzidos, recortados de fontes disponíveis ao pesquisador e selecionados a partir de operações de lógica formal: informações recorrentes no mesmo sentido são colados no texto e as informações discordantes são selecionadas, descartando-se a supostamente errada ou inexata. Além disso, também se usou a distinção entre memória, memória coletiva, história e esquecimento, presentes, sobretudo, nos trabalhos de Maurice Halbwachs Paul Ricoeur, bem como as noções de progresso e da historia magistra vitae, que aparecem sobretudo nos relatos produzidos no século XX. Esta Fábrica, que foi uma dos primeiros empreendimentos industriais do Brasil, cuja origem remonta ao século XVI, despertou o interesse de várias personalidades, como Pedro Taques, Martim Francisco, José Bonifácio, Vergueiro, Varnhagen e Calógeras, entre outros que escreveram sobre esse estabelecimento por diversas razões, em especial, para sustentar-se o pioneirismo de Ipanema em face de outras fábricas existentes em Minas Gerais, destacando, ademais, a intriga entre o primeiro diretor, o sueco Carl Gustav Hedberg e seu sucessor, Frederico Luis Guilherme Varnhagen. No século XX, esses relatos buscavam analisar os malogros da siderurgia nacional até a década de 1970, na intenção de obterem-se lições do passado. / This dissertation examines the construction of history and memory of the Fabrica de Ferro de São João de Ipanema, in Sorocaba, from the RG Collingwoods approach, who created the wellknown concept of scissors-and-paste\" history, in order to criticize historical writings or historiographical practices in which their authors work uncritically with produced reports, getting them from available sources to the researcher and selected from formal logic operations: similar information remain in the text and conflicting information are selected, discarding the supposedly wrong or inaccurate ones. A distintion among memory, collective memory, history and forgetting was made, present mainly in the work of Maurice Halbwachs Paul Ricoeur, and the concepts of progress and history magistra vitae, which appear mainly in the reports produced in the 20th Century. This plant, which was one of the first industrial activities in Brazil, whose origin was in the 16th Century, was object of interest of several people, like Peter Taques, Martim Francisco, Jose Bonifacio, Vergueiro, Varnhagen and Calógeras, among others who wrote about Ipanema for various reasons, in particular, to stress the pioneering of Ipanema in the face of other plants in Minas Gerais, noting, moreover, the conspiracy between the first Ipanemas Director, the Swedish Carl Gustav Hedberg and his successor, the German Frederico Luis Guilherme Varnhagen. In the 20th Century, these reports sought to examine the failures of the national steel industry until the 1970s, in order to get to lessons of the past.

Essa dissertação analisa a construção da história e da memória da Fábrica de Ferro de São João de Ipanema, na região de Sorocaba, a partir do referencial teórico de R.G. Collingwood, o qual formulou a conhecida história de cola e tesoura, com o intuito de questionar escritas da história ou práticas historiográficas em que seus autores apenas trabalham de maneira acrítica com relatos já produzidos, recortados de fontes disponíveis ao pesquisador e selecionados a partir de operações de lógica formal: informações recorrentes no mesmo sentido são colados no texto e as informações discordantes são selecionadas, descartando-se a supostamente errada ou inexata. Além disso, também se usou a distinção entre memória, memória coletiva, história e esquecimento, presentes, sobretudo, nos trabalhos de Maurice Halbwachs Paul Ricoeur, bem como as noções de progresso e da historia magistra vitae, que aparecem sobretudo nos relatos produzidos no século XX. Esta Fábrica, que foi uma dos primeiros empreendimentos industriais do Brasil, cuja origem remonta ao século XVI, despertou o interesse de várias personalidades, como Pedro Taques, Martim Francisco, José Bonifácio, Vergueiro, Varnhagen e Calógeras, entre outros que escreveram sobre esse estabelecimento por diversas razões, em especial, para sustentar-se o pioneirismo de Ipanema em face de outras fábricas existentes em Minas Gerais, destacando, ademais, a intriga entre o primeiro diretor, o sueco Carl Gustav Hedberg e seu sucessor, Frederico Luis Guilherme Varnhagen. No século XX, esses relatos buscavam analisar os malogros da siderurgia nacional até a década de 1970, na intenção de obterem-se lições do passado. / This dissertation examines the construction of history and memory of the Fabrica de Ferro de São João de Ipanema, in Sorocaba, from the RG Collingwoods approach, who created the wellknown concept of scissors-and-paste\" history, in order to criticize historical writings or historiographical practices in which their authors work uncritically with produced reports, getting them from available sources to the researcher and selected from formal logic operations: similar information remain in the text and conflicting information are selected, discarding the supposedly wrong or inaccurate ones. A distintion among memory, collective memory, history and forgetting was made, present mainly in the work of Maurice Halbwachs Paul Ricoeur, and the concepts of progress and history magistra vitae, which appear mainly in the reports produced in the 20th Century. This plant, which was one of the first industrial activities in Brazil, whose origin was in the 16th Century, was object of interest of several people, like Peter Taques, Martim Francisco, Jose Bonifacio, Vergueiro, Varnhagen and Calógeras, among others who wrote about Ipanema for various reasons, in particular, to stress the pioneering of Ipanema in the face of other plants in Minas Gerais, noting, moreover, the conspiracy between the first Ipanemas Director, the Swedish Carl Gustav Hedberg and his successor, the German Frederico Luis Guilherme Varnhagen. In the 20th Century, these reports sought to examine the failures of the national steel industry until the 1970s, in order to get to lessons of the past.

Os eletrodos de pasta de carbono modificados com Azul da Prússia foram preparados usando a voltametria cíclica, deposição a um potencial controlado e a deposição a dois potenciais controlados. O último método foi melhor e produziu eletrodos modificados com alta sensibilidade e estabilidade durante a redução catalítica de peróxido de hidrogênio. A composição da solução modificadora foi 3,0 mmol L-1 de FeCl3 e 2,0 mmol L-1 de K3[Fe(CN)6] em pH 2,0 com HCI. O sistema de eletrodos foi imerso na solução modificadora e + 0,4 V foi aplicado no eletrodo de trabalho durante 2 minutos. Depois, o potencial foi revertido para - 0,4 V por mais 2 minutos. O processo total foi repetido mais duas vezes. Além disso, para melhorar a estabilidade dos eletrodos de pasta de carbono modificados com Azul da Prússia (EPC-AP), estes foram ciclados em solução contendo 1,0 m mol L-1 de RhCl3, 0,05 mol L-1 de KCI e 0,02 mol L-1 de HCI na faixa de potencial - 0,4V ≤ Eapl ≤ 0,6V a 60 mV s-1 (50 ciclos). Estes eletrodos, denominados de EPC-AP-Rh, foram secos a temperatura ambiente por 24 horas antes de serem utilizados. Os EPC-AP-Rh apresentaram boa estabilidade durante sucessivos ciclos, com os picos anódico e catódico, referentes a 0,30 V e 0,18 V inicialmente atribuídos para um processo redox envolvendo Branco da Prússia / Azul da Prússia. Cálculos com (Ep,a + Ep,c / 2), é 0,24 V. Em solução tampão citrato de potássio / ácido cítrico contendo 0,5 mol L-1 de KCI, pH 6,1, as correntes de picos variam linearmente com a velocidade de varredura 0,025 Vs-1 ≤ ν ≤ 0,400 V s-1 mostrando que o processo é governado por difusão de íons do eletrólito suporte para a superfície do eletrodo (durante a etapa de redução) ou do eletrodo para a solução (durante a etapa de oxidação) para manter a eletroneutralidade. O excesso superficial foi 4,3 10-8 mol cm-2, calculado usando a carga anódica obtida pelo voltamograma cíclico, depois da subtração do fundo de carga referente a um eletrodo não modificado de pasta de carbono em solução eletrólito suporte (1,0 x 10-3 mol L-1 de RhCl3, 0,05 mol L-1 de KCI e 0,02 mol L-1 de HCI, ν = 60 mV s-1). O eletrólito suporte usado para detecção para determinação de peróxido de hidrogênio foi o tampão10 mmol L-1 de citrato de potássio/ 2 mmol L-1 de ácido cítrico, pH 6,1 (força iônica= 0,16 mol L-1) contendo 0,5 mol L-1 de KCI. A ausência deste eletrólito ou a presença de íons fosfatos diminui a estabilidade deste sensor. Peróxido de hidrogênio foi determinado a 0,04 V (vs EAg/AgCI, KCI sat) na faixa linear de 5,1 x 10-5 mol L-1 a 8,6 x 10-4 mol L-1 com sensibilidade média de 1,4 ± 0,2 A mol-1 L cm-2 e limite de detecção de (2,5 ± 0,02) x 10-5 mol L-1. Neste potencial aplicado a contribuição da corrente de redução do oxigênio foi de 8,0 % na presença de 1,0 mmol L-1 de H2O2. Curvas analíticas obtidas durante a determinação de peróxidos de hidrogênio ao longo de 5 dias, cada curva analítica representa uma média de 6 curvas amperométricas consecutivas, que desempenhou em cada dia, apresentando uma diminuição de somente 27% na sensibilidade do eletrodo modificado. Quando fora de uso o eletrodo foi armazenado em solução 0,5 mol L-1 de KCI. A um potencial aplicado de 0,04 V não foi detectada uma interferência do mediador ou oxidação direta do ácido úrico. A interferência de ácido ascórbico foi apenas significativa para potenciais iguais ou superiores a 0,060 V. / Prussian Blue carbon paste modified electrodes were prepared using cyclic voltammetry and deposition atone and two controlled potentials. The last method was the best and produced modified electrodes with higher sensitivity and stability during the catalytic reduction of hydrogen peroxide. The composition of the modifying solution was 3.0 mmol L-1 FeCl3, 2.0 mmol L-1 K3[Fe(CN)6] in pH 2.0 with HCI. The electrode system was immersed in the modifying solution and + 0.4 V was applied to the working electrode during two minutes. After, the potential was just reverted to - 0.4 V once more two minutes. The total process was repeated twice. Further, to improve the stability of the Prussian Blue carbon paste modified electrodes (PB-CPME), they were cycled in a solution containing 1.0 mmol L-1 RhCl3, 0,05 mol L-1 KCI and 0.02 mol L-1 HCI in a - 0.4 ≤ E ≤ 0.6 V potential range at 60 mV s-1 (50 cycles). These electrodes, denominated of Rh-PBCPME, were dried at ambient temperature during 24 hours before use. The Rh-PBCPME shows good stability during successive cycles, with anodic and cathodic peaks recorded at 0.30 V and 0.18 V being attributed to a redox process involving Prussian White / Prussian Blue couple. Em, calculated as (Ep,a + Ep,c/2), is 0.24 V. In potassium citrate/ citric acid buffer solution containing 0.5 mol L-1 KCI, pH 6.1, the peak currents changed linearly with the square of sweep velocity in the range 0.025 Vs-1 ≤ v ≤ 0.400 Vs-1 showing that the process is governed by ion diffusion from support electrolyte to the electrode surface (during the reduction step) or from the electrode to the solution (during the oxidation step) to ensure the electroneutrality rule. The modifier surface excess was 4.3 x 10-8 mol cm-2, calculated using the anodic charge obtained from cyclic voltammograms, after subtraction of the background charge recorded with an unmodified carbon paste electrode in an electrolyte support solution (1.0 mmol L-1 RhCl3, 0.5 mol L-1 KCI and 0.02 mol L-1 HCI, v = 60 mV s-1). The supporting electrolyte used to detection of hydrogen peroxide was 10 mmol L-1 potassium citrate/ 2 mmol L-1 Citric acid buffer, pH 6.1 (ionic strength = 0.16 mol L-1) containing 0.5 mol L-1 KCI. The absence of this electrolyte or the presence of phosphate ions decreased the stability of the sensor. Hydrogen peroxide was detected at 0.04V (vs EAg/AgCI, KCI sat) in 5.1 x 10-5 - 8.6 x 10-4 mol L-1 linear range with sensitivity of 1.4 ± 0.2) A mo1-1 L cm-2 and detection limit of (2.5 ± 0.02) x 10-5 mol L-1. At this applied potential the contribution of oxygen reduction current was 8.0 % in the presence of 1.0 mmol L-1 H2O2. Analytical curves obtained during hydrogen peroxide detections along 5 days, ach one of them representing an average of 6 consecutive amperometric analytical curves, carried out in the same day, showed a decrease of only 27 % in the sensitivity of the modified electrodes. When was not using the electrode was kept, 0.5 mol L-1 KCI. At 0.04 V applied potential no interference was detected due to mediated or direct oxidation of uric acid. The interference of ascorbic acid was only significant to 0.060 V or higher applied potentials.

In September 2008 Hurricane Ike hit the Texas Gulf Coast with a force stronger than the category 2 storm at which it was rated. With a 3.8 m (12.5 ft) storm surge, the agricultural industry in the area was devastated. The goal of this research was to determine the length of time required to reduce the salt levels brought by the storm surge to near pre-hurricane levels. To do this, four sets of samples were taken across two years and analyzed for salinity using the saturated paste extract method. The initial salt levels in November 2008 had an electrical conductivity (ECe) of the inundated soils as high as 26.7 dS/m. Fifty-four percent of the soils sampled in the 0-15 cm horizons and 9% in the 15-30 cm horizons of the edge area had an ECe >= 4 dS/m. In the surge area 79% of the soils sampled in the 0-15 cm horizons and 30% in the 15-30 cm horizons had an ECe >= 4 dS/m. In April 2009, 38% of the soils sampled in the 0-15 cm horizons and 13% in the 15-30 cm horizons of the edge area had an ECe >= 4 dS/m. In the surge area 71% of the soils sampled in the 0-15 cm horizons and 39% in the 15-30 cm horizons had an ECe >= 4 dS/m. By December 2009, none of the soils sampled in the edge area had an ECe >= 4 dS/m. In the surge area 21% of the soils sampled in the 0-15 cm horizons and 33% in the 15-30 cm horizons had an ECe >= 4 dS/m. By October 2010, all soils sampled had leached sufficient salts to be classified as non-saline to very slightly saline soils. Utilizing the November 2008 data set, 28 random samples were selected for exchangeable Na percent (ESP) in order to develop the ESP-SAR (Na adsorption ratio) predictive equation, ESP= 1.19(SAR)^0.82. The SAR-ESP relationship is statistically significant (95% confidence level), with a correlation coefficient of 0.964 (df=26).

Dans cette thèse, les travaux présentés s’appuient sur une démarche expérimentale utilisant, outre les mesures destructives habituellement mises en œuvre pour la caractérisation des matériaux cimentaires, les techniques non destructives exploitant la propagation des ondes ultrasonores à des fréquences comprises entre 50 kHz et 600 kHz. L’objectif est d’étudier les corrélations entre les propriétés hydrauliques et mécaniques de la pâte de ciment et les paramètres linéaires des ondes ultrasonores (vitesse et atténuation). L’étude concerne plus particulièrement les relations entre la porosité et la vitesse ultrasonore des différents types d’onde (ondes de volume et onde de Rayleigh). Les matériaux étudiés sont des pâtes de ciment à porosité variable, confectionnées avec différents rapports E/C et avec différents dosages en entraineur d’air. Afin de prendre en compte l’effet de la teneur en eau, les mesures sont effectuées à différents états de saturation : état saturée, 70% de saturation, 30% de saturation et l’état sec. Les données recueillies permettent la constitution d’une base des données expérimentale regroupant les caractéristiques physiques, mécaniques et ultrasonores de la pâte de ciment. Dans la dernière partie de cette thèse, les relations entre les vitesses ultrasonores et la porosité basées sur deux approches macroscopique et microscopique sont présentées et confrontées aux mesures / In this thesis, we present an experimental study including, besides the destructive measurements usually implemented for the characterization of cementitious materials, non-destructive techniques using ultrasonic wave propagation in a frequency range from 50kHz to 600kHz. The objective is to study the correlations between hydraulic, mechanical properties and linear ultrasonic parameters (velocity and attenuation) of cement paste. This study specifically addresses the relationship between porosity and ultrasonic velocity of the different types of waves (body waves and Rayleigh wave). The studied materials are cement pastes with variable porosity, made up with different water / cement ratios and with different concentrations of air entrainer. To take into account the effect of water content, measurements are made at different states of saturation: saturated state, 70% saturation, 30% saturation and dry state. The data collected allows the creation of a database of experimental data involving physical, mechanical and ultrasonic parameters of cement paste. In the final part of this thesis, relationships between ultrasonic velocity and porosity based on macroscopic and microscopic approaches are presented and compared with measurements

La carbonatation est une pathologie qui affecte les matériaux à base de ciment tels que les bétons et lesmortiers. Les zones carbonatées du matériau deviennent fragiles et perdent ainsi leur pouvoir deprotection des aciers contre la corrosion. Les produits de corrosion engendrent alors une dégradation dubéton pouvant aboutir à la ruine de la structure.Six types de bétons adjuvantés et deux pâtes de ciments ont été formulés grâce à une étude rhéologiqueafin d’étudier l’effet de la carbonatation accélérée et naturelle sur la durabilité des bétons et des pâtesde ciments à base de ressources algériennes. Pour ce faire, plusieurs méthodes d’investigation sontutilisées, aussi bien à l’échelle macroscopique que microscopique.En conclusion, le modèle rhéologique empirique développé peut être utilisé pour formuler des bétonsrésistants à la carbonatation. L’étude de la carbonatation démontre que le protocole accéléré, peut serévéler moins agressifs que la carbonatation naturelle, notamment pour des pâtes de ciment denses.Dans ce cas, la carbonatation accélérée de la surface tend à combler la microporosité superficielle dubéton, freinant ainsi la diffusion du dioxyde de carbone, contrairement à la carbonatation naturelle quiagit de manière plus diffuse sans totalement obstruer la porosité. Moins les bétons sont compacts, plusle protocole accéléré s’avère effectif. / The carbonation is a pathology which affects cement-based materials such as concretes and mortars.The carbonated skin of material becomes brittle and losses the protection of inner steels againstcorrosion. The corrosion products generate a degradation of the concrete which may lead to thecollapse of the structure.Six types of adjuvant concretes and two cement pastes have been designed by a rheological study inorder to study the effect of accelerated and natural carbonation on the sustainability of concretes andcement pastes based on algerian resources. For this purpose, several investigation methods were usedwith both macroscopic and microscopic scales.In conclusion, the empirical rheological model developed herein can be used to formulate concretesresistant to carbonation. The study of carbonation shows that the accelerated protocol may be lessaggressive than the natural one, especially for dense cement pastes. In this case, the acceleratedcarbonation of the surface tends to fill up the superficial microporosity of the concrete, slowing downthe production of carbon dioxide, contrary to the natural carbonation which acts more diffusely withoutcompletely obstructing the pores. The lesser compact is the concrete, the more effective is theaccelerated protocol.

Une part importante de la détérioration des réseaux d’assainissement en matériau cimentaire est d’origine biologique. Dans ce contexte, les matériaux à base de ciment alumineux ont montré une meilleure durabilité que ceux à base de ciment Portland ordinaire, couramment utilisés. Les hypothèses de la littérature qui expliqueraient cette meilleure résistance sont centré sur l’aluminium (présent à plus de 50% dans les ciments alumineux pour seulement 5% dans les ciments Portland). L’objectif de cette thèse est de caractériser et hiérarchiser les mécanismes de résistance des matériaux cimentaires lors de la biodétérioration. Cela permettra de comprendre le rôle de l’aluminium dans les interactions entre les microorganismes et les matériaux cimentaires. Après des études en réacteur et des tests de biodétérioration de pâte de ciments en laboratoire, il semblerait que la principale cause de résistance est due à la réactivité des matrices cimentaires plus qu’à un effet inhibiteur de l’aluminium ou du matériau sur les microorganismes. / An important part of the deterioration observed in concrete sewer networks is due to biological activity. In this context, calcium aluminate cement (CAC) based material has shown a better durability than ordinary Portland cement, usually used in such context. In literature, hypothesis explaining the better resistance are focused on aluminium. The aim of the project is to characterize the role of aluminium in the interactions between cementitious material and microorganisms. Reactor study and Lab scale aggressive biodeterioration protocol of cementitious material revealed that the better resistance of CAC is due to their lower reactivity and not to a bacteriostatic effect of the material on the microorganisms.

Ces travaux s’intéressent au comportement de pâtes de ciment de différentes natures cimentaires exposées à une eau douce naturelle et plus particulièrement aux interactions avec les éléments biologiques. Cette étude est basée sur l’analyse comparative d’échantillons placés en milieu naturel (Moselle) et en milieux artificiels de laboratoire. Quels que soient les milieux et les microorganismes considérés, les résultats montrent une modification de la minéralogie de la surface et du réseau poreux des échantillons (taux de porosité, propriétés de transferts). Les essais en laboratoire ont permis d’isoler l’influence spécifique des bactéries dans les phénomènes de biolixiviation. Le dénombrement bactérien montre aussi que la densité de cellules présentes dans le biofilm recouvrant les échantillons dépend peu de la nuance cimentaire, excepté pour les ciments au calcaire. Les observations au MEB ont révélé, sur l’ensemble des échantillons, la présence abondante de diatomées en partie recouvertes par une couche minérale issue d’une cristallisation secondaire. La colonisation de la surface par ces diatomées est influencée par la géométrie et la nature minéralogique des échantillons. Les résultats d’essais en laboratoire ont montré qu’elles ont des interactions avec la pâte de ciment, l’évolution des densités de population de diatomées coïncide en effet avec l’évolution des caractéristiques de porosité (taux de porosité, propriétés de transferts) / This work focuses on the behavior of cement pastes of different cement bases exposed to natural fresh water and on the interactions with the biological elements. This study is based on the comparative analysis of samples immersed in natural environment (Moselle) and in artificial laboratory media. Whatever the media and microorganisms considered, the results show a change in the mineralogy of the surface and the porous network of the samples (porosity rate, transfer properties). Laboratory tests highlighted the specific influence of bacteria in bioleaching phenomena. The bacterial count also shows that the density of cells present in the biofilm covering the samples does not mainly depend on the cementitious grade, except for the limestone cements. The SEM observations revealed the abundant presence of diatoms on all samples. Diatoms are partly covered by a mineral layer resulting from secondary crystallization. The colonization of the surface by these diatoms is influenced by the geometry and mineralogical nature of the samples. The results of laboratory tests have shown that they interact with cement paste; the evolution of diatom population densities coincides with changes in porosity characteristics (porosity rate, transfer properties)

Ce travail de thèse est consacré à la caractérisation des propriétés mécaniques de l’interphase pâte de ciment-granulat au cours de l’hydratation et au cours de la dégradation chimique par lixiviation. La microstructure de l'interphase entre la pâte de ciment et les granulats est caractérisée par une porosité supérieure à celle de la pâte de ciment. Cette zone constitue un point de fragilité dans le béton et ses propriétés affectent fortement le comportement mécanique du béton à l’échelle macroscopique et à l’échelle de la structure. Dans ce travail, la résistance de l’interphase pâte de ciment-granulat est analysée expérimentalement à l'échelle locale. Des essais expérimentaux sont réalisés sur des composites constitués de granulats liés par une pâte de ciment portland préparée avec un rapport Eau/Ciment de 0,5. Des dispositifs expérimentaux dédiés ont été conçus et réalisés de manière à être adaptés à la taille et à la forme des échantillons. La forme des échantillons utilisés et les outils expérimentaux développés permettent de solliciter directement l’interphase. A différents stades de l'hydratation, des échantillons de pâte de ciment seule et des composites sont soumis à des essais de compression, de traction et de cisaillement direct. L’étude des propriétés mécaniques de l’interphase pâte de ciment-granulat révèle une faiblesse de cette zone en termes de propriétés mécaniques..Le protocole expérimental mis au point a permis d’étudier les effets du mécanisme de lixiviation du calcium au niveau de l’interphase sur les propriétés mécaniques du béton à l’échelle locale. Compte tenu du temps caractéristique long du phénomène de lixiviation, la mise en situation expérimentale au laboratoire est accélérée en remplaçant l’eau par une solution de nitrate d'ammonium. Afin de quantifier le développement et la cinétique de dégradation au niveau de la liaison cimentée, les fronts de lixiviation du béton sont caractérisés à différents degrés de dégradation en utilisant la phénolphtaléine comme traceur. Des essais mécaniques locaux (compression, traction et cisaillement) sont réalisés sur les composites et sur la pâte de ciment à différents temps de dégradation. L’étude de l’effet de la lixiviation à l’échelle locale montre le rôle important de l’interphase pâte de ciment-granulat lors du processus de dégradation chimique sur les propriétés mécaniques du composite. / In this work, we presents an experimental study to characterize the mechanical properties at the local scale of the cement paste-aggregate interface during hydration and during chemical degradation by leaching.It is generally accepted that the microstructure of the interface between the aggregates and the cement paste is characterized by a higher porosity than that of cement paste. This makes this zone a weak point in the concrete. The particular properties of this zone strongly influence the mechanical behavior of concrete. In this work, the mechanical properties of the cement paste-aggregate composite, are experimentally studied. The experimental tests are performed on composites at classical aggregate scale (one centimeter of section). These composite are composed by and Portland cement paste and aggregate. The cement paste is prepared with a water/cement ratio of 0.5. The shape of the prepared composites makes them convenient for direct tensile and shear tests. At different stages of hydration, we performed direct tensile and shear tests on the composites by means of specific devices. The same tests were carried out on the cement paste in order to compare with composites results. The shape of the prepared composites makes them convenient to characterize the cement paste-aggregate interface. At different stages of hydration, the composites are subjected to compression tests, direct tensile tests or shear tests. The study of the mechanical properties of the cement-aggregates interface revealed that the cement paste-aggregate interface is the weakest zone in the composite.An experimental protocol was developed to study the effects of calcium leaching mechanism at the cement paste-aggregate interface on the mechanical properties of the concrete. As the process of leaching with the deionised water occurs very slowly, the experimental study in the laboratory is accelerated by replacing the water by ammonium nitrate solution. To quantify the development and kinetics of degradation at the cemented bond, the concrete leaching fronts are characterized at different levels of degradation by using phenolphthalein. Local mechanical tests (compression, tensile and shear) are performed on composite and cement paste at different stages of degradation. The experimental results show that there is a leaching effect on the alteration of the mechanical properties at the cement paste-aggregate interface.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / In this work was developed an electroanalytical methodology for determination of the antibiotic minocycline in pharmaceutical formulation and in human milk using differential pulse voltammetry. The voltammograms of the minocycline obtained with carbon paste electrodes showed a well-defined peak at 0.40 V vs. Ag/AgCl, corresponding to the oxidation of minocycline at pH 4.0. The electrodic behavior involved a reversible oxidation process and mass transport controlled by diffusion. The value of the effective area calculated for the carbon paste electrode was 0.3313 cm2, corresponding to a geometric area of 0.0078 cm2. After the optimization of the experimental conditions, such as, pH 4.00; scan speed 30 mV s-1, amplitude 100 mV; analytical curves were obtained in the linear concentration range from 2.0 to 23 μmol L-1 resulting in a detection limit of 0.7 μmol L-1 and the quantification limit of 2.2 μmol L-1. In order to evaluate the robustness of the proposed method the presence of possible interfering was analyzed in the determination of the minocycline, it was observed the interference of the folic acid, ketoconazole and dipyridamole among the possible evaluated interfering. To check the applicability of the developed method were analyzed previously in the optimized conditions, commercial samples of pharmaceutical formulations, one liquid and another in tablet, obtaining a recovery of 100 and 99.3%, respectively; and samples of maternal milk, obtaining a recovery of 96%. In addition to advantages such as high selectivity and sensitivity, the method developed could be used for the analysis of minocycline in pharmaceutical formulation and human milk without any need for prior sample treatment. / Neste trabalho foi desenvolvido uma metodologia eletroanalítica para a determinação do antibiótico minociclina em formulação farmacêutica e em leite materno usando voltametria de pulso diferencial. Os voltamogramas da minociclina obtidos com eletrodos de pasta de carbono apresentaram um pico bem definido em 0,40 V vs. Ag/AgCl, correspondente à oxidação da minociclina em pH 4,0. O comportamento eletródico envolveu um processo de oxidação reversível e um transporte de massa controlado por difusão. O valor da área efetiva calculada para o eletrodo de pasta de carbono foi de 0,3313 cm2, correspondente a uma área geométrica de 0,0078 cm2. Após a otimização das condições experimentais, a saber, pH 4,00; velocidade de varredura 30 mV s-1, amplitude 100 mV, curvas analíticas foram obtidas na faixa linear de concentração de 2,0 a 23 μmol L-1 resultando em um limite de detecção de 0,70 μmol L-1 e um limite de quantificação de 2,2 μmol L-1. A fim de avaliar a robustez do método proposto foi analisada a presença de possíveis interferentes na determinação da minociclina, sendo observado a interferência do ácido fólico, cetoconazol e dipiridamol dentre os possíveis interferentes avaliados. Para verificar a aplicabilidade do método desenvolvido foram analisadas nas condições previamente otimizadas, amostras comerciais de formulações farmacêuticas, uma líquida e outra em comprimido, obtendo uma recuperação de 100 e 99,3%, respectivamente; e amostras de leite materno, obtendo uma recuperação de 96%. Além das vantagens como alta seletividade e sensibilidade, o método desenvolvido pode ser usado para análise de minociclina em formulação farmacêutica e em leite materno sem a necessidade de tratamento prévio da amostra.