Jairo Andrade | Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS) (original) (raw)
Papers by Jairo Andrade
Sustainability
The search for new alternative materials for employment in the construction industry is necessary... more The search for new alternative materials for employment in the construction industry is necessary for more sustainable development. The construction demolition waste (CDW), as well as by-products generated by initiatives, such as slag, fly ash (FA), palm oil fuel ash (POFA), metakaolin (MK), silica fume (SF), and rice husk ash (RHA), are objects of studies in several segments of the civil construction sector. The addition of these wastes to the materials currently used to produce concrete and mortar can be one of the significant efforts to achieve more sustainable construction. The use of these wastes in the construction sector can bring considerable benefits in terms of costs, energy efficiency, and environmental and ecological benefits. Over the years, many types of research have been developed aiming at the possibility of a practical use of CDW as an aggregate and industrial by-product (FA, POFA, MK, SF, RHA) as pozzolans. Based on recent studies, this paper reviews the current s...
A manutenção predial bem planejada e executada proporciona manutenção da vida útil e do desempenh... more A manutenção predial bem planejada e executada proporciona manutenção da vida útil e do desempenho das edificações, porém a impressão é a de que falta este conhecimento aos construtores e gerenciadores, o que origina intervenções emergenciais. Além disso, pode também influenciar na sensação de bem-estar das pessoas propiciando ambientes bem conservados. É necessário que a manutenção predial preventiva cresça no mercado pois somente com ela é possível manter os níveis de desempenho exigidos pela atual norma de desempenho. Por este cenário e pelas motivações expostas, esta pesquisa tem como objetivo entender como as empresas e condomínios tratam da manutenção em suas edificações e tentar qualificá-la a partir da opinião dos usuários, através da aplicação de questionários. Os resultados apresentaram que a maioria das empresas não possui programa de manutenção, com exceção das empresas de manutenção. Segundo as informações apresentadas pelos usuários, a melhor gestão de manutenção é a realizada pelos shoppings e a pior é a realizada pelas indústrias. Quase a totalidade afirmou que o estado de conservação interfere no seu conforto, que evitam retornar a locais com más condições e a maioria afirmou que não se importa em pagar um pouco a mais por serviços de melhor qualidade.
Ambiente Construído, 2008
The corrosion of reinforcement due the action of chloride ions (Cl-) is one of the most common da... more The corrosion of reinforcement due the action of chloride ions (Cl-) is one of the most common damages in reinforced concrete structures, decreasing the durability of those structures. The durability may be numerically expressed by the service life and the solutions from the second Fick`s Law are normally used to obtain service life values. This paper presents the results of a study on the applicability of the error function solution using two cement types: CP B and CP IV. Concretes were produced with three w/c ratios (0,4; 0,5; 0,6), and submitted to compressive strength and the chloride ingress tests over a period of 6 months. The results showed that the compressive strength and the diffusion coefficient (D) were higher for CP B than for CP IV. The value of D decreased along the test period for both types of cement, resulting in an increase of the estimated concrete service life. As the error function solution does not consider the variation of the parameter D, it does not adequat...
Considering the high demand for increased productivity and reduced production costs, the Reliabil... more Considering the high demand for increased productivity and reduced production costs, the Reliability Engineering is important in order to reduce failures in production processes. In this context, this paper presents the application of reliability concepts for analysis and prioritization of the main failure modes incidents in an automatic capacitor assembly machine, in a company of Rio Grande do Sul, Brazil. For this study were performed a monitoring device during a period of 3 months. Based in failure data, the 4 most significant failure modes have been defined. These failure modes were analyzed by distributing more appropriate probability as compliance tests for location of the failure mode in the bathtub curve. Were proposed actions to reduce the failure rate, as well as definition of what kind of maintenance is most appropriate for the observed failure modes. The results after the execution of the proposed actions were increased productivity and overall efficiency of the equipment.
Frente a escassez dos recursos naturais e a dificuldade na destinação de grandes volumes de resíd... more Frente a escassez dos recursos naturais e a dificuldade na destinação de grandes volumes de resíduos na indústria da construção civil, apresenta-se necessária a busca por alternativas sustentáveis que solucionem ambos os problemas, sendo a incorporação de Resíduos de Construção e Demolição (RCD) em concretos uma destas práticas sustentáveis. Sua análise e caracterização demonstrou, entre outras características, maior porosidade e permeabilidade, propriedades as quais geralmente levam a redução de resistência do concreto. Contudo, estas características mostram-se positivas em situações de congelamento devido à capacidade de dissipação dos efeitos do aumento do volume da água passível de congelamento pelo seu alto índice de vazios. Neste contexto, este trabalho avaliou os efeitos do congelamento em concretos realizados com a incorporação de RCD. Para tanto, foram realizados ensaios em concretos com 25%, 50%, 75% e 100% de substituição de agregados naturais pelos reciclados e submetidos a um ciclo de gelo e degelo com duração de 144h. Por fim, as amostras foram ensaiadas para verificação da absorção e da resistência à compressão. Os resultados mostraram que a incorporação de 25% e 50% de RCD ao concreto não altera de modo considerável sua absorção d'água, enquanto a incorporação de 25%, 50% e 75% de RCD ao concreto mostra pequena variação nos valores de resistência à compressão residual, após 48h de congelamento.
Abstract: The main objective of this paper is to use the techniques and methods of Product Proces... more Abstract: The main objective of this paper is to use the techniques and methods of Product Process Development in the equipment development for a technology-based small business. Conceptual design concepts were generated and through the use of a morphological matrix the options of confection of the final conceptual prototype were verified. With the definition of the previous steps, the project team cataloged the main requirements and functions of the equipment and compared and evaluated them with a reference concept already used in the external environment of the company, verifying their priorities through the Mudge Method. Subsequently, the study of the needs of improvements in the main functions was done creating a final functional prototype for use in the work environment. The application of these techniques allowed quantifying the productivity of the product manufactured by equipment, comparing the situation before and after the process with the new equipment. In addition it was...
DYNA, 2019
The overall equipment effectiveness (OEE) is an indicator used in the management and continuous i... more The overall equipment effectiveness (OEE) is an indicator used in the management and continuous improvement of production systems, and is useful in identifying losses, thus reducing production costs. By analyzing the results of this indicator, the operation manager must make decisions to eliminate or reduce losses in the process. This study investigated the application of the OEE indicator in one production line in the pulp and paper industry. The implementation of OEE was performed in stages with a detailed analysis of the indicators that compose the OEE (quality, performance, and availability) to identify possible improvements. Thus, actions were implemented to improve the OEE quality index. This study provided important information that enabled the operation manager to diagnose and minimize the occurrence of failures and losses, which is often hidden and unknown to those involved in the production system.
DYNA, 2019
Electric power distribution companies are facing a delicate moment. Privatizations, scarce resour... more Electric power distribution companies are facing a delicate moment. Privatizations, scarce resources, few investments and harsh penalties due to lack of quality force these companies to seek greater efficiency and control of their processes. Thus, making decisions based only on tacit knowledge and without a clear procedure, like the maintenance company that was part of this study, is not advisable. For this reason, this work aimed to develop a support tool for maintenance decisions, based on failure data and criticality analysis. The FMEA (Failure Mode and Effect Analysis) method was used to discover the riskiest failure modes, and the MAUT (Multi-Attribute Utility Theory) and the Mudge method were used to rank the main criteria used by experts when deciding which transmission line (TL) is in a more critical condition. As a result, the study proposed a tool that guides decision-making in a systematized, impersonal and collective knowledge-based manner for the specific situations enc...
MOJ Civil Engineering, 2018
The use of stone dust in concrete provides environmental benefits by reducing the impacts produce... more The use of stone dust in concrete provides environmental benefits by reducing the impacts produced by the extraction of natural sand. The use of this material can also offer economic advantages, since the product is less costly than natural sand. In this way, the present work evaluated the compressive strength of concretes made with stone dust in different replacement levels (30% and 100%) compared to the use of natural sand. The results were analyzed statistically using the Analysis of Variance (ANOVA) in order to verify the statistical influence of replacement levels and the mix proportioning in the resulting compressive strength. It was found that the compressive strength of concrete with 30% of replacement level presented similar behavior to reference concrete, showing that the use in structural concrete is feasible.
Journal of Building Pathology and Rehabilitation, 2019
Reinforced concrete structures are subjected to several degradation processes that often occur ea... more Reinforced concrete structures are subjected to several degradation processes that often occur early, especially due to reinforcements corrosion. Therefore, the use of representative models for an accurate service-life prediction of reinforced concrete structures becomes indispensable. Thus, this study is aimed at evaluating the model proposed by Andrade to efficiently predict the chloride penetration in concrete structures. In addition, the input variables of this model, as well as the challenges in obtaining them are analyzed. Andrade's model was applied in some case studies to verify their efficiency in predicting the chloride penetration in reinforced concrete structures in marine environments. The results indicate that for data with small exposure times, the model yielded similar responses to the chloride penetration in situ, with good results within an error range of 35%, associated with a maximum difference of only 4.6 mm between observed and calculated values. For the data with higher exposure times, the differences were significant, indicating the need for an alteration in order to best determine the increase in surface chloride concentration over time. Thus, it is suggested that the model undergoes modifications, mainly in relation to two fundamental aspects, (i) adopt the growth of the chloride surface concentration over time and (ii) consider the variability of the concrete characteristics and exposure conditions through a probabilistic approach.
Sustainability, 2019
Many current industrial processes, such as water treatment, produce large amounts of waste. The w... more Many current industrial processes, such as water treatment, produce large amounts of waste. The water treatment sludge (WTS) must be properly disposed of and/or used as raw material for application in other sectors, such as the construction industry. The rendering mortar production can be an environmentally friendly alternative to recycle the WTS, this being the object of this research. In this way, mortars were produced with 2.5%, 5%, 7.5%, and 10% calcined WTS to replace natural sand. The water absorption, compressive strength, bond strength, and flexural strength properties were evaluated. A natural carbonation was carried out for the determination of CO2 uptake due to carbonation. The results showed that the incorporation of calcined WTS has an influence on all the properties evaluated. Considering 50 years of service life, the CO2 uptake potential for mortar with 10% calcined sludge WTP is 111 kg CO2/t. In the sustainability approach, it was observed that CO2 uptake due to carb...
Matéria (Rio de Janeiro), 2019
RESUMO O presente trabalho tem como objetivo principal investigar a potencialidade do emprego de ... more RESUMO O presente trabalho tem como objetivo principal investigar a potencialidade do emprego de lodo de estação de tratamento de água (ETA) moído e calcinado em substituição ao agregado miúdo em concretos de cimento Portland, assim evitando o descarte em aterros sanitários e se tornando uma possível alternativa de reutilização desse material. Foram avaliados os efeitos dos teores de substituição de areia pelo lodo de ETA (2,5%, 5%, 7,5% e 10% em massa) e da relação a/c (0,4, 0,5 e 0,6) nas propriedades físicas (massa específica, porosidade e absorção de água por imersão) e mecânicas (resistências à compressão axial e à tração por compressão diametral) em diferentes idades (7, 28 e 91 dias). Todos os dados coletados foram analisados estatisticamente, empregando-se a análise de variância (ANOVA). Os resultados mostraram que, apesar da minimização das propriedades em comparação com o concreto de referência, todos os concretos apresentaram valores de resistência à compressão maiores qu...
Journal of Building Pathology and Rehabilitation, 2017
Nowadays an amount of reinforced concrete structures are presenting problems related with corrosi... more Nowadays an amount of reinforced concrete structures are presenting problems related with corrosion of reinforcement, mainly that induced by chloride ions. So, many studies are being accomplished to predict the necessary time for chloride ions reach the reinforcement, beginning the propagation of corrosive process. In this paper, three models were selected for analysis to determine their ability in properly predicting the chloride penetration in concrete structures: the solution of 2nd Fick's Law, the complete solution of 2nd Fick's Law, considering the variation of diffusion coefficient and the superficial concentration of chlorides in time; and a model proposed. Analysis of the formulations principles and assessment and applicability of equations were made, taking into account the adequate choice of parameters and variables involved, the difficulty to obtain these parameters, and if the models represent properly the natural phenomena. In order to contribute with the service life prediction of the structures when inserted in saline environments, a mathematical model was developed based in a Focus Groups analysis. Some of the main characteristics of the proposed model are the logic applied for its development and the application easiness. This model was applied in a case study to verify the answer in relation to chloride penetration in some points of a reinforced concrete structure inserted in a saline area. The behavior of the model was consistent with the results of experimental investigations accomplished by other researchers.
Matéria (Rio de Janeiro), 2017
RESUMO O revestimento de argamassa já é utilizado há muitos anos e continua sendo muito empregado... more RESUMO O revestimento de argamassa já é utilizado há muitos anos e continua sendo muito empregado ainda nos dias de hoje com o surgimento de novas tendências. Apesar disso, tal subsistema não acompanhou a evolução de outras tecnologias, como o concreto estrutural. Está cada vez mais comum a ocorrência de manifestações patológicas em revestimentos argamassados quando executados sobre estrutura de concreto. Segundo estudos, a ocorrência destas manifestações, especialmente quando aplicado em substratos de concreto, está ligada ao aumento da resistência e da diminuição da porosidade do mesmo. Nesse contexto, este artigo tem como objetivo verificar a perda de aderência de chapiscos com o aumento da resistência do concreto e definir o melhor tipo de chapisco para utilizar sobre este tipo de substrato. Foram moldadas placas de concreto, com variação da resistência característica (fck) de 17,75 MPa, 29,89 MPa e 35,15 MPa. As placas foram chapiscadas com chapisco convencional, rolado e desem...
Construction and Building Materials, 2009
... Karine Krummenauer a and Jairo José de Oliveira Andrade Corresponding Author Contact Informat... more ... Karine Krummenauer a and Jairo José de Oliveira Andrade Corresponding Author Contact Information , a , E-mail The Corresponding Author. ... The fibers are used in asphalt mixtures for two main reasons: (1) to increase the toughness and fracture resistance of the hot mix and (2 ...
Sustainability
The search for new alternative materials for employment in the construction industry is necessary... more The search for new alternative materials for employment in the construction industry is necessary for more sustainable development. The construction demolition waste (CDW), as well as by-products generated by initiatives, such as slag, fly ash (FA), palm oil fuel ash (POFA), metakaolin (MK), silica fume (SF), and rice husk ash (RHA), are objects of studies in several segments of the civil construction sector. The addition of these wastes to the materials currently used to produce concrete and mortar can be one of the significant efforts to achieve more sustainable construction. The use of these wastes in the construction sector can bring considerable benefits in terms of costs, energy efficiency, and environmental and ecological benefits. Over the years, many types of research have been developed aiming at the possibility of a practical use of CDW as an aggregate and industrial by-product (FA, POFA, MK, SF, RHA) as pozzolans. Based on recent studies, this paper reviews the current s...
A manutenção predial bem planejada e executada proporciona manutenção da vida útil e do desempenh... more A manutenção predial bem planejada e executada proporciona manutenção da vida útil e do desempenho das edificações, porém a impressão é a de que falta este conhecimento aos construtores e gerenciadores, o que origina intervenções emergenciais. Além disso, pode também influenciar na sensação de bem-estar das pessoas propiciando ambientes bem conservados. É necessário que a manutenção predial preventiva cresça no mercado pois somente com ela é possível manter os níveis de desempenho exigidos pela atual norma de desempenho. Por este cenário e pelas motivações expostas, esta pesquisa tem como objetivo entender como as empresas e condomínios tratam da manutenção em suas edificações e tentar qualificá-la a partir da opinião dos usuários, através da aplicação de questionários. Os resultados apresentaram que a maioria das empresas não possui programa de manutenção, com exceção das empresas de manutenção. Segundo as informações apresentadas pelos usuários, a melhor gestão de manutenção é a realizada pelos shoppings e a pior é a realizada pelas indústrias. Quase a totalidade afirmou que o estado de conservação interfere no seu conforto, que evitam retornar a locais com más condições e a maioria afirmou que não se importa em pagar um pouco a mais por serviços de melhor qualidade.
Ambiente Construído, 2008
The corrosion of reinforcement due the action of chloride ions (Cl-) is one of the most common da... more The corrosion of reinforcement due the action of chloride ions (Cl-) is one of the most common damages in reinforced concrete structures, decreasing the durability of those structures. The durability may be numerically expressed by the service life and the solutions from the second Fick`s Law are normally used to obtain service life values. This paper presents the results of a study on the applicability of the error function solution using two cement types: CP B and CP IV. Concretes were produced with three w/c ratios (0,4; 0,5; 0,6), and submitted to compressive strength and the chloride ingress tests over a period of 6 months. The results showed that the compressive strength and the diffusion coefficient (D) were higher for CP B than for CP IV. The value of D decreased along the test period for both types of cement, resulting in an increase of the estimated concrete service life. As the error function solution does not consider the variation of the parameter D, it does not adequat...
Considering the high demand for increased productivity and reduced production costs, the Reliabil... more Considering the high demand for increased productivity and reduced production costs, the Reliability Engineering is important in order to reduce failures in production processes. In this context, this paper presents the application of reliability concepts for analysis and prioritization of the main failure modes incidents in an automatic capacitor assembly machine, in a company of Rio Grande do Sul, Brazil. For this study were performed a monitoring device during a period of 3 months. Based in failure data, the 4 most significant failure modes have been defined. These failure modes were analyzed by distributing more appropriate probability as compliance tests for location of the failure mode in the bathtub curve. Were proposed actions to reduce the failure rate, as well as definition of what kind of maintenance is most appropriate for the observed failure modes. The results after the execution of the proposed actions were increased productivity and overall efficiency of the equipment.
Frente a escassez dos recursos naturais e a dificuldade na destinação de grandes volumes de resíd... more Frente a escassez dos recursos naturais e a dificuldade na destinação de grandes volumes de resíduos na indústria da construção civil, apresenta-se necessária a busca por alternativas sustentáveis que solucionem ambos os problemas, sendo a incorporação de Resíduos de Construção e Demolição (RCD) em concretos uma destas práticas sustentáveis. Sua análise e caracterização demonstrou, entre outras características, maior porosidade e permeabilidade, propriedades as quais geralmente levam a redução de resistência do concreto. Contudo, estas características mostram-se positivas em situações de congelamento devido à capacidade de dissipação dos efeitos do aumento do volume da água passível de congelamento pelo seu alto índice de vazios. Neste contexto, este trabalho avaliou os efeitos do congelamento em concretos realizados com a incorporação de RCD. Para tanto, foram realizados ensaios em concretos com 25%, 50%, 75% e 100% de substituição de agregados naturais pelos reciclados e submetidos a um ciclo de gelo e degelo com duração de 144h. Por fim, as amostras foram ensaiadas para verificação da absorção e da resistência à compressão. Os resultados mostraram que a incorporação de 25% e 50% de RCD ao concreto não altera de modo considerável sua absorção d'água, enquanto a incorporação de 25%, 50% e 75% de RCD ao concreto mostra pequena variação nos valores de resistência à compressão residual, após 48h de congelamento.
Abstract: The main objective of this paper is to use the techniques and methods of Product Proces... more Abstract: The main objective of this paper is to use the techniques and methods of Product Process Development in the equipment development for a technology-based small business. Conceptual design concepts were generated and through the use of a morphological matrix the options of confection of the final conceptual prototype were verified. With the definition of the previous steps, the project team cataloged the main requirements and functions of the equipment and compared and evaluated them with a reference concept already used in the external environment of the company, verifying their priorities through the Mudge Method. Subsequently, the study of the needs of improvements in the main functions was done creating a final functional prototype for use in the work environment. The application of these techniques allowed quantifying the productivity of the product manufactured by equipment, comparing the situation before and after the process with the new equipment. In addition it was...
DYNA, 2019
The overall equipment effectiveness (OEE) is an indicator used in the management and continuous i... more The overall equipment effectiveness (OEE) is an indicator used in the management and continuous improvement of production systems, and is useful in identifying losses, thus reducing production costs. By analyzing the results of this indicator, the operation manager must make decisions to eliminate or reduce losses in the process. This study investigated the application of the OEE indicator in one production line in the pulp and paper industry. The implementation of OEE was performed in stages with a detailed analysis of the indicators that compose the OEE (quality, performance, and availability) to identify possible improvements. Thus, actions were implemented to improve the OEE quality index. This study provided important information that enabled the operation manager to diagnose and minimize the occurrence of failures and losses, which is often hidden and unknown to those involved in the production system.
DYNA, 2019
Electric power distribution companies are facing a delicate moment. Privatizations, scarce resour... more Electric power distribution companies are facing a delicate moment. Privatizations, scarce resources, few investments and harsh penalties due to lack of quality force these companies to seek greater efficiency and control of their processes. Thus, making decisions based only on tacit knowledge and without a clear procedure, like the maintenance company that was part of this study, is not advisable. For this reason, this work aimed to develop a support tool for maintenance decisions, based on failure data and criticality analysis. The FMEA (Failure Mode and Effect Analysis) method was used to discover the riskiest failure modes, and the MAUT (Multi-Attribute Utility Theory) and the Mudge method were used to rank the main criteria used by experts when deciding which transmission line (TL) is in a more critical condition. As a result, the study proposed a tool that guides decision-making in a systematized, impersonal and collective knowledge-based manner for the specific situations enc...
MOJ Civil Engineering, 2018
The use of stone dust in concrete provides environmental benefits by reducing the impacts produce... more The use of stone dust in concrete provides environmental benefits by reducing the impacts produced by the extraction of natural sand. The use of this material can also offer economic advantages, since the product is less costly than natural sand. In this way, the present work evaluated the compressive strength of concretes made with stone dust in different replacement levels (30% and 100%) compared to the use of natural sand. The results were analyzed statistically using the Analysis of Variance (ANOVA) in order to verify the statistical influence of replacement levels and the mix proportioning in the resulting compressive strength. It was found that the compressive strength of concrete with 30% of replacement level presented similar behavior to reference concrete, showing that the use in structural concrete is feasible.
Journal of Building Pathology and Rehabilitation, 2019
Reinforced concrete structures are subjected to several degradation processes that often occur ea... more Reinforced concrete structures are subjected to several degradation processes that often occur early, especially due to reinforcements corrosion. Therefore, the use of representative models for an accurate service-life prediction of reinforced concrete structures becomes indispensable. Thus, this study is aimed at evaluating the model proposed by Andrade to efficiently predict the chloride penetration in concrete structures. In addition, the input variables of this model, as well as the challenges in obtaining them are analyzed. Andrade's model was applied in some case studies to verify their efficiency in predicting the chloride penetration in reinforced concrete structures in marine environments. The results indicate that for data with small exposure times, the model yielded similar responses to the chloride penetration in situ, with good results within an error range of 35%, associated with a maximum difference of only 4.6 mm between observed and calculated values. For the data with higher exposure times, the differences were significant, indicating the need for an alteration in order to best determine the increase in surface chloride concentration over time. Thus, it is suggested that the model undergoes modifications, mainly in relation to two fundamental aspects, (i) adopt the growth of the chloride surface concentration over time and (ii) consider the variability of the concrete characteristics and exposure conditions through a probabilistic approach.
Sustainability, 2019
Many current industrial processes, such as water treatment, produce large amounts of waste. The w... more Many current industrial processes, such as water treatment, produce large amounts of waste. The water treatment sludge (WTS) must be properly disposed of and/or used as raw material for application in other sectors, such as the construction industry. The rendering mortar production can be an environmentally friendly alternative to recycle the WTS, this being the object of this research. In this way, mortars were produced with 2.5%, 5%, 7.5%, and 10% calcined WTS to replace natural sand. The water absorption, compressive strength, bond strength, and flexural strength properties were evaluated. A natural carbonation was carried out for the determination of CO2 uptake due to carbonation. The results showed that the incorporation of calcined WTS has an influence on all the properties evaluated. Considering 50 years of service life, the CO2 uptake potential for mortar with 10% calcined sludge WTP is 111 kg CO2/t. In the sustainability approach, it was observed that CO2 uptake due to carb...
Matéria (Rio de Janeiro), 2019
RESUMO O presente trabalho tem como objetivo principal investigar a potencialidade do emprego de ... more RESUMO O presente trabalho tem como objetivo principal investigar a potencialidade do emprego de lodo de estação de tratamento de água (ETA) moído e calcinado em substituição ao agregado miúdo em concretos de cimento Portland, assim evitando o descarte em aterros sanitários e se tornando uma possível alternativa de reutilização desse material. Foram avaliados os efeitos dos teores de substituição de areia pelo lodo de ETA (2,5%, 5%, 7,5% e 10% em massa) e da relação a/c (0,4, 0,5 e 0,6) nas propriedades físicas (massa específica, porosidade e absorção de água por imersão) e mecânicas (resistências à compressão axial e à tração por compressão diametral) em diferentes idades (7, 28 e 91 dias). Todos os dados coletados foram analisados estatisticamente, empregando-se a análise de variância (ANOVA). Os resultados mostraram que, apesar da minimização das propriedades em comparação com o concreto de referência, todos os concretos apresentaram valores de resistência à compressão maiores qu...
Journal of Building Pathology and Rehabilitation, 2017
Nowadays an amount of reinforced concrete structures are presenting problems related with corrosi... more Nowadays an amount of reinforced concrete structures are presenting problems related with corrosion of reinforcement, mainly that induced by chloride ions. So, many studies are being accomplished to predict the necessary time for chloride ions reach the reinforcement, beginning the propagation of corrosive process. In this paper, three models were selected for analysis to determine their ability in properly predicting the chloride penetration in concrete structures: the solution of 2nd Fick's Law, the complete solution of 2nd Fick's Law, considering the variation of diffusion coefficient and the superficial concentration of chlorides in time; and a model proposed. Analysis of the formulations principles and assessment and applicability of equations were made, taking into account the adequate choice of parameters and variables involved, the difficulty to obtain these parameters, and if the models represent properly the natural phenomena. In order to contribute with the service life prediction of the structures when inserted in saline environments, a mathematical model was developed based in a Focus Groups analysis. Some of the main characteristics of the proposed model are the logic applied for its development and the application easiness. This model was applied in a case study to verify the answer in relation to chloride penetration in some points of a reinforced concrete structure inserted in a saline area. The behavior of the model was consistent with the results of experimental investigations accomplished by other researchers.
Matéria (Rio de Janeiro), 2017
RESUMO O revestimento de argamassa já é utilizado há muitos anos e continua sendo muito empregado... more RESUMO O revestimento de argamassa já é utilizado há muitos anos e continua sendo muito empregado ainda nos dias de hoje com o surgimento de novas tendências. Apesar disso, tal subsistema não acompanhou a evolução de outras tecnologias, como o concreto estrutural. Está cada vez mais comum a ocorrência de manifestações patológicas em revestimentos argamassados quando executados sobre estrutura de concreto. Segundo estudos, a ocorrência destas manifestações, especialmente quando aplicado em substratos de concreto, está ligada ao aumento da resistência e da diminuição da porosidade do mesmo. Nesse contexto, este artigo tem como objetivo verificar a perda de aderência de chapiscos com o aumento da resistência do concreto e definir o melhor tipo de chapisco para utilizar sobre este tipo de substrato. Foram moldadas placas de concreto, com variação da resistência característica (fck) de 17,75 MPa, 29,89 MPa e 35,15 MPa. As placas foram chapiscadas com chapisco convencional, rolado e desem...
Construction and Building Materials, 2009
... Karine Krummenauer a and Jairo José de Oliveira Andrade Corresponding Author Contact Informat... more ... Karine Krummenauer a and Jairo José de Oliveira Andrade Corresponding Author Contact Information , a , E-mail The Corresponding Author. ... The fibers are used in asphalt mixtures for two main reasons: (1) to increase the toughness and fracture resistance of the hot mix and (2 ...