Demands for using electrical resistivity techniques (surface and bulk resistivity) as an alternative to the rapid chloride penetrability test (RCPT) have been growing, for example by a number of transportation agencies in North America, to give an indication of the relative penetrability of concrete. While resistivity measurements may reflect the quality of pore structure in the cementitious matrix, their accuracy might be affected by a multitude of parameters including the concentration of ionic species in the pore solution, particularly when supplementary cementitious materials (SCMs) are incorporated in the binder. Hence, a systematic investigation on the resistivity of concrete and its corresponding physical penetrability is warranted. Zinc sacrificial anodes are considered an effective and economical method to prevent the electrochemical corrosion of steel bars by providing cathodic current to bars, which can provide corrosion protection at low galvanic current densities in the range of 0.2 to 2 mA/m2. Sacrificial anodes are commonly used in RC structures particularly in bridge decks to mitigate a critical phenomenon that occurs in the original concrete beside the repaired patches, which is known as the ‘halo effect’. One of the key factors affecting the efficacy of zinc anodes is the resistivity of concrete or cementitious repair material in which these anodes are embedded. There is a general notion that the higher the electrical resistivity of concrete or repair material, the less likely that zinc anodes produce the target galvanic current for optimum protection of steel bars. However, no systematic data are available on the maximum allowable electrical resistivity of repair materials/concretes beyond which zinc anodes cannot properly function to prevent corrosion. In the first part of this thesis, a tripartite relationship (nomogram) to correlate surface resistivity with penetrability (migration coefficient) and porosity of concrete using a wide range ii of concrete mixtures, taking into account the effect of key mixture design parameters (water-to-binder ratio, air-entrainment, SCMs and type of cement) was established. Relationships between surface and bulk resistivity as well as migration coefficient and porosity of concrete were also introduced. In addition, a penetrability classification of concrete based on the corresponding ranges of surface resistivity, migration coefficient and porosity has been proposed. The nomogram and penetrability classification provided reasonable assessment for the condition of field cores extracted from newly constructed and aging concrete pavement. In the second part of this thesis, the functionality of zinc anodes at mitigating patch accelerated corrosion (halo effect) in repaired concrete was explored. Concrete slabs were cast to simulate the patch repair configuration in the field, and the main parameters in this study were changing the resistivity of the repair section in the slabs (5,000, 15,000, 25,000, 50,000 and 100,000 Ω-cm), and anode spacing (25, 100, and 250 mm) inside the repair patch. Analysis of current and potential data shows a high level of effectiveness of the anodes at controlling corrosion in this slab configuration up to 52 weeks under a wetting-drying exposure. / February 2017

A obtenção do Cermet de níquel-zircônia via moagem de alta energia (Mechanical Alloying MA) foi estudado visando a preparação de anodos de células a combustível de óxido sólido (SOFC). O níquel metálico foi adicionado em três concentrações: 30, 40 e 50% em volume. As operações de moagem foram conduzidas em moinho vibratório de alta energia do tipo SPEX. Estudou-se a influência do tempo de moagem, a eficiência de aditivos para controle do processo, tipo e geometria dos potes de moagem. A influência destas variáveis foram avaliadas através de análises de tamanho de partículas, determinação de área superficial e morfologia do material resultante. O uso de pote de teflon resultou em contaminação por carbono. Por outro lado, o uso de pote de aço aumenta a contaminação por impurezas metálicas. As diversas geometrias projetadas para os potes mostraram que potes com maiores raios de concordância (R.15) apresentaram melhor rendimento. Após a conformação e sinterização a 1300°C em atmosfera de argônio, as amostras apresentaram valores de densidade entre 60 a 80% da densidade teórica. As microestruturas observadas por microscopia eletrônica de varredura revelaram uma boa homogeneidade na distribuição de fases do Cermet. A técnica de moagem de alta energia apresentou-se como boa opção na fabricação de Cermet Ni-ZrO2. / The ZrO2 and metallic Ni Cermet obtained by Mechanical Alloying MA is studied in the present work with the objective to prepare solid oxide fuel cells anodes (SOFC). Metallic Ni is added under three different concentrations: 30, 40 and 50% volume. The millings were conducted in SPEX vibratory mill where the influence of milling time, process control additives efficiency, type and geometry of milling vessels were studied. The study of the influence of these variables was made under particle size analysis, surface area determination and resulting material morphology. The use of teflon vessel causes contamination by carbon. On the other side, steel vessel increases the contamination by metallic impurities. The several geometries projected and analyzed for the vessels showed that vessels with larger bottom radius (R.15) showed the best results. After conformation and sintering at 1300°C in argon atmosphere the samples reached densities between 60 and 80% of the theoretical density. Microstructures observed by scanning electron microscopy reveal good homogeneity in the Cermet phases distribution. The mechanical alloying technique was considered a good option to obtain Ni- ZrO2 Cermet.

A obtenção do Cermet de níquel-zircônia via moagem de alta energia (Mechanical Alloying MA) foi estudado visando a preparação de anodos de células a combustível de óxido sólido (SOFC). O níquel metálico foi adicionado em três concentrações: 30, 40 e 50% em volume. As operações de moagem foram conduzidas em moinho vibratório de alta energia do tipo SPEX. Estudou-se a influência do tempo de moagem, a eficiência de aditivos para controle do processo, tipo e geometria dos potes de moagem. A influência destas variáveis foram avaliadas através de análises de tamanho de partículas, determinação de área superficial e morfologia do material resultante. O uso de pote de teflon resultou em contaminação por carbono. Por outro lado, o uso de pote de aço aumenta a contaminação por impurezas metálicas. As diversas geometrias projetadas para os potes mostraram que potes com maiores raios de concordância (R.15) apresentaram melhor rendimento. Após a conformação e sinterização a 1300°C em atmosfera de argônio, as amostras apresentaram valores de densidade entre 60 a 80% da densidade teórica. As microestruturas observadas por microscopia eletrônica de varredura revelaram uma boa homogeneidade na distribuição de fases do Cermet. A técnica de moagem de alta energia apresentou-se como boa opção na fabricação de Cermet Ni-ZrO2. / The ZrO2 and metallic Ni Cermet obtained by Mechanical Alloying MA is studied in the present work with the objective to prepare solid oxide fuel cells anodes (SOFC). Metallic Ni is added under three different concentrations: 30, 40 and 50% volume. The millings were conducted in SPEX vibratory mill where the influence of milling time, process control additives efficiency, type and geometry of milling vessels were studied. The study of the influence of these variables was made under particle size analysis, surface area determination and resulting material morphology. The use of teflon vessel causes contamination by carbon. On the other side, steel vessel increases the contamination by metallic impurities. The several geometries projected and analyzed for the vessels showed that vessels with larger bottom radius (R.15) showed the best results. After conformation and sintering at 1300°C in argon atmosphere the samples reached densities between 60 and 80% of the theoretical density. Microstructures observed by scanning electron microscopy reveal good homogeneity in the Cermet phases distribution. The mechanical alloying technique was considered a good option to obtain Ni- ZrO2 Cermet.

The durability of concrete structures is affected by a number of factors such as environmental exposure, electrochemical reactions, mechanical loading, impact damage and others. Of all of these, corrosion of the reinforcement is probably the main cause for the deterioration of steel reinforced concrete (RC) structures. Corrosion management is becoming increasingly necessary as a result of the growing number of ageing infrastructure assets (e.g. bridges, tunnels etc.) and the increased requirement for unplanned maintenance in order to keep these structures operational throughout their design life (and commonly, beyond). The main RC repair, refurbishment and rehabilitation approaches generally employed can be broadly categorised under a) conventional, b) surface treatments, c) electrochemical treatments and d) design solutions. The overarching aim of this research was to identify the key corrosion management techniques and undertake empirical investigations focused on full-scale RC structures to investigate their long-term performance. To achieve this, individual research packages were identified from the above broad five approaches for repair, replacement and rehabilitation. These were 1) Patch repairs and incipient anodes, 2) Impressed Current Cathodic Protection, 3) Galvanic Cathodic Protection and 4) Hydrophobic treatments. The selection of the above research packages was based on past and present use by the construction industry to repair, refurbish and rehabilitate RC structures. Their contributions may be broadly categorised as i) Investigations on how specific treatments and materials perform, ii) Investigations on the effectiveness of existing methods of measurements and developing alternatives, iii) Changes to the existing theory of corrosion initiation and arrest and iv) Changes to management framework strategies. The key findings from each research package can be summarised as follows: Macrocell activity appears to be a consequence rather than a cause of incipient anode formation in repaired concrete structures, as has previously been presented; ICCP has persistent protective effects even after interruption of the protective current; Discrete galvanic anodes installed in the parent concrete surrounding the patch repair are a feasible alternative to galvanic anodes embedded within the patch repairs of RC structures; Silanes may have a residual hydrophobic effect even after 20 years of service.

Thèse de doctorat : sciences. Dispositifs de l'électronique intégrée : Ecully, Ecole centrale de Lyon : 2003. / Titre provenant de l'écran-titre. 189 réf.

Thèse de doctorat : sciences. Dispositifs de l'électronique intégrée : Ecully, Ecole centrale de Lyon : 2003. / 189 réf.

Thesis (M.S.)--University of Delaware, 2007. / Principal faculty advisors: Jingguang G. Chen, Dept. of Chemical Engineering; and Thomas P. Beebe, Jr., Dept. of Chemistry & Biochemistry. Includes bibliographical references.

Thesis (Ph. D.)--University of Alberta, 2010. / Title from pdf file main screen (viewed on June 25, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Materials Engineering, [Department of] Chemical and Materials Engineering, University of Alberta. Includes bibliographical references.

Thesis (Ph.D.) - University of St Andrews, March 2008. / Restricted until 14th March 2009.

Thesis (Ph.D.) - University of St Andrews, October 2009.