Made available in DSpace on 2017-06-01T17:57:31Z (GMT). No. of bitstreams: 1 dissertacao_clerio_bezerra.pdf: 3171938 bytes, checksum: 2c69909d4369b39648102f2f200d89ec (MD5) Previous issue date: 2011-06-13 / The corrosion by chlorides is considered by a number of researchers the most dangerous pathological manifestation attacking concrete reinforcements. The assessment of the attacks to the structure by sodium chloride is usually done in the laboratory, takes too long and costs too much. The.main reason for this work is to assess the presence of free chlorides in Portland cement concrete and mortar through the silver nitrate aspersion method, which is justified by the fact that Our objective is to evaluate the applicability of the silver nitrate aspersion method in loco, in Portland-cement-based materials as indicators capable of showing the presence or not of contamination by chlorides, avoiding the immediate need for lab tests. So as to give credibility to the test for presence of free chlorides in the samples, these were checked by means of electrochemical tests in parallel with the silver nitrate aspersion. The experimental results of these tests showed that the applicability of the silver nitrate aspersion method seems to be of great relevance in the technical environment, as it is a qualitative method, easily applicable, inexpensive and capable of providing quick information so that professionals can safely diagnose the levels of chloride corrosion in the structures / A corrosão por cloretos é considerada por muitos pesquisadores a mais severa das manifestações patológicas que atacam as armaduras. O objetivo principal deste trabalho é avaliar a presença de cloretos livres em concreto de cimento Portland pelo método de aspersão de solução de nitrato de prata. A verificação de ataque por cloreto na estrutura é normalmente feita através de exames laboratoriais, demorados em que apresentam um custo muito alto. Pesquisando a aplicabilidade do método de aspersão de nitrato de prata in loco, em materiais à base de cimento Portland como indicador com capacidade de informar a presença ou não de contaminação por cloretos, evitando assim de imediato o teste laboratorial. Para que os resultados destes ensaios tivessem credibilidade quanto à presença de cloretos livres nas amostras, foi realizado, paralelamente à aspersão de nitrato de prata, um acompanhamento das amostras através de ensaios eletroquímicos. Observou-se com os resultados experimentais da pesquisa que a aplicabilidade do método de aspersão de solução de nitrato de prata vem a ser de grande relevância para o meio técnico, por ser um método qualitativo, de fácil aplicação, barato e provendo informações rápidas para que os profissionais da área de engenharia possam diagnosticar com segurança as estruturas com corrosão contaminadas por cloreto

Made available in DSpace on 2017-06-01T17:57:32Z (GMT). No. of bitstreams: 1 Ronaldo Pontes.pdf: 4668306 bytes, checksum: 48d4fe1ec07bae512f5d789ae55d9ec8 (MD5) Previous issue date: 2006-03-30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Exposing concrete structures to the saline mist, they can suffer chlorides attacks and could cause reinforcement corrosion. The structures parts with faces directed to dominant winds are more susceptible, especially those with great surface in relation to the volume, such as pillars and beams. This work objective is to evaluate the level of marine aggressiveness, in marine edge of Boa Viagem quarter, Recife-PE, in function of the distance to the sea, measuring the value of chloride deposition, using the wet candle method, with the support of the environment management. The results indicate that chloride ions reach surface structure in different levels of concentration, depending on the distance from its origin, in this case, the sea. The conclusion is that chloride deposition decreases, in an exponential relation, when there is an increase of the distance to the sea, and that aggressiveness is significantly as far as 400 m from the marine edge / Diante da exposição à névoa salina, as estruturas em concreto podem sofrer ataques por cloretos, provocando corrosão das armaduras. As peças com faces voltadas aos ventos dominantes estão mais suscetíveis, especialmente aquelas que possuem grande superfície em relação ao volume, como são os casos de pilares e vigas. Este trabalho tem como objetivo avaliar os níveis de agressividade marinha, na orla marítima do Bairro de Boa Viagem, Recife-PE, em função de sua distância em relação ao mar, medindo a taxa de deposição de cloretos, pelo método da vela úmida, tendo como apoio o monitoramento do ambiente. Os resultados indicam que os íons cloreto chegam à superfície das estruturas a distintos níveis de concentração, dependendo da distância em relação à sua fonte geradora, no caso, o mar. Conclui-se que a deposição de cloretos decresce, numa relação do tipo exponencial, à medida que há um aumento do distanciamento em relação ao mar, e que a agressividade é significativa até 400 m da orla marítima

No description available.

The aim of this study was to assess the strength, durability properties and corrosion resistance of concrete samples using supplementary cementitious blended materials. In this investigation, three supplementary concrete materials (SCMs) were used together with ordinary Portland Cement (OPC) to form cementitious blends at different proportions. The supplementary materials are silica fume (SF), ground granulated blast furnace slag (GGBS) and fly ash (FA). Sixteen (16) different proportions of the cementitious blends were produced. Tests carried out on concrete samples include slump test, compressive strength, oxygen permeability, sorptivity, porosity, chloride conductivity test, resistance to chloride and sulphate attack. The electrode potentials of tested samples were also observed using electrochemical measurements. Concrete specimens prepared with 10%, 20%, 30%, 40%, up to 60% of blended cements replacement levels were evaluated for their compressive strength at, 7, 14, 28, 90 and 120 days while the specimens were evaluated for durability tests at 28, and 90 days respectively. The results were compared with ordinary Portland cement concrete without blended cement. Voltage, and temperature measurements were also carried out to understand the quality of concrete. The corrosion performance of steel in reinforced concrete was studied and evaluated by electrochemical half-cell potential technique in both sodium chloride, and magnesium sulphate solutions respectively. The reinforced concrete specimens with centrally embedded 12mm steel bar were exposed to chloride and sulphate solutions with the 0.5 M NaCl and MgSO4 concentrations respectively. An impressed voltage technique was carried out to evaluate the corrosion resistance of the combination of quaternary cementitious blended cement, so as to get the combination with optimum performance. Improvement of strength, durability, and corrosion resistance properties of blended concrete samples are observed at different optimum percentages for binary, ternary and quaternary samples. The effect of cementitious blends is recognized in limiting the corrosion potential of the tested SCM concrete samples. Generally, the cementitious blends with limited quantity of SF to 10% have the potential to produce satisfactory concrete. These should however be used for low cost construction, where high quality concrete is not required. / Civil and Chemical Engineering / M. Tech. (Chemical Engineering)