Péter Ludvig - Academia.edu (original) (raw)
Papers by Péter Ludvig
Seminário de Discentes dos Programas de Pós-Graduação Stricto Sensu, Sep 5, 2018
Lecture Notes in Civil Engineering, 2021
À minha esposa Priscila, pelo amor e apoio mesmo nos momentos difíceis, pessoa sem a qual eu nunc... more À minha esposa Priscila, pelo amor e apoio mesmo nos momentos difíceis, pessoa sem a qual eu nunca teria chegado ao Brasil e nem teria entrado no "mundo da pesquisa". Ao meu orientador Prof. Dr. José Marcio Fonseca Calixto, por ter acreditado em mim, pela paciência, apoio e pelo carinho e amizade durante estes quatro anos. Ao meu co-orientador Prof. Dr. Luiz Orlando Ladeira, pela atenção e motivação, fazendo com que eu me envolvesse no "universo nano".
Os concretos de ultra-alto desempenho (CUAD) sao materiais a base de cimento que apresentam resis... more Os concretos de ultra-alto desempenho (CUAD) sao materiais a base de cimento que apresentam resistencia a compressao superior a 150 MPa, suas propriedades mecânicas e de durabilidade se apresentam superiores se comparadas aos concretos de alto desempenho e aos concretos convencionais Estudos recentes indicam que a incorporacao de nanotubos de carbono como reforco da matriz de CUAD pode resultar na melhoria de sua microestrutura e consequentemente, melhorar a sua durabilidade frente a ataques como a carbonatacao e a penetracao de ions de cloreto. A presente pesquisa tem por objetivo delinear o estado da arte em torno da durabilidade de CUAD com matriz reforcada com nanotubos de carbono, principalmente sobre o fenomeno da carbonatacao. Nesse sentido utilizou-se o metodo Proknow-C, um processo estruturado para selecao e analise de referencias bibliograficas; atraves do qual construiu-se um portfolio de artigos que foram analisados. Os resultados da pesquisa evidenciam que ainda ha lacu...
Construction and Building Materials, 2020
Abstract Ultra High Performance Concretes (UHPC) are known for exceptional mechanical and durabil... more Abstract Ultra High Performance Concretes (UHPC) are known for exceptional mechanical and durability properties due to optimized particle packing and a denser microstructure. However, the very tight packing of particles resulting in a dense microstructure can be a cause of problems in UHPCs when exposed to higher temperatures. The low porosity delays the movement of water vapour inside de concrete and a layer of condensed water is created, preventing water to escape the microstructure and increasing internal pressure, that may result in explosive spalling. In this research, carbon nanotubes (CNTs) were introduced in UHPCs to assess their influence on the properties after exposition to high temperatures. Specimens were subjected to slow and fast heating rates and occurrence of spalling was investigated. Mechanical tests, such as compressive strength (before heating and after heating) and splitting tensile strength were conducted to investigate the impact of CNTs on the mechanical properties. Gas permeability tests were performed to investigate alterations in porosity due to the presence of CNTs. Results show that the presence of CNTs can reduce the occurrence of spalling at additions of 0.05% and 0.10% by weight of cement. CNTs can also increase the residual strength at temperatures up to 300 °C at a slow heating rate. At the same time, the 28-day compressive and splitting tensile strengths remained unaltered and oxygen permeability coefficients were reduced when CNTs were added to the matrix.
Seminário de Discentes dos Programas de Pós-Graduação Stricto Sensu, Sep 5, 2018
Lecture Notes in Civil Engineering, 2021
À minha esposa Priscila, pelo amor e apoio mesmo nos momentos difíceis, pessoa sem a qual eu nunc... more À minha esposa Priscila, pelo amor e apoio mesmo nos momentos difíceis, pessoa sem a qual eu nunca teria chegado ao Brasil e nem teria entrado no "mundo da pesquisa". Ao meu orientador Prof. Dr. José Marcio Fonseca Calixto, por ter acreditado em mim, pela paciência, apoio e pelo carinho e amizade durante estes quatro anos. Ao meu co-orientador Prof. Dr. Luiz Orlando Ladeira, pela atenção e motivação, fazendo com que eu me envolvesse no "universo nano".
Os concretos de ultra-alto desempenho (CUAD) sao materiais a base de cimento que apresentam resis... more Os concretos de ultra-alto desempenho (CUAD) sao materiais a base de cimento que apresentam resistencia a compressao superior a 150 MPa, suas propriedades mecânicas e de durabilidade se apresentam superiores se comparadas aos concretos de alto desempenho e aos concretos convencionais Estudos recentes indicam que a incorporacao de nanotubos de carbono como reforco da matriz de CUAD pode resultar na melhoria de sua microestrutura e consequentemente, melhorar a sua durabilidade frente a ataques como a carbonatacao e a penetracao de ions de cloreto. A presente pesquisa tem por objetivo delinear o estado da arte em torno da durabilidade de CUAD com matriz reforcada com nanotubos de carbono, principalmente sobre o fenomeno da carbonatacao. Nesse sentido utilizou-se o metodo Proknow-C, um processo estruturado para selecao e analise de referencias bibliograficas; atraves do qual construiu-se um portfolio de artigos que foram analisados. Os resultados da pesquisa evidenciam que ainda ha lacu...
Construction and Building Materials, 2020
Abstract Ultra High Performance Concretes (UHPC) are known for exceptional mechanical and durabil... more Abstract Ultra High Performance Concretes (UHPC) are known for exceptional mechanical and durability properties due to optimized particle packing and a denser microstructure. However, the very tight packing of particles resulting in a dense microstructure can be a cause of problems in UHPCs when exposed to higher temperatures. The low porosity delays the movement of water vapour inside de concrete and a layer of condensed water is created, preventing water to escape the microstructure and increasing internal pressure, that may result in explosive spalling. In this research, carbon nanotubes (CNTs) were introduced in UHPCs to assess their influence on the properties after exposition to high temperatures. Specimens were subjected to slow and fast heating rates and occurrence of spalling was investigated. Mechanical tests, such as compressive strength (before heating and after heating) and splitting tensile strength were conducted to investigate the impact of CNTs on the mechanical properties. Gas permeability tests were performed to investigate alterations in porosity due to the presence of CNTs. Results show that the presence of CNTs can reduce the occurrence of spalling at additions of 0.05% and 0.10% by weight of cement. CNTs can also increase the residual strength at temperatures up to 300 °C at a slow heating rate. At the same time, the 28-day compressive and splitting tensile strengths remained unaltered and oxygen permeability coefficients were reduced when CNTs were added to the matrix.
Construction and Building Materials, 2020
Abstract The mortar behavior depends on the rheological characteristics, and the interaction and ... more Abstract The mortar behavior depends on the rheological characteristics, and the interaction and proportion between its components, which can affect mechanical and durability properties, and also can generate pathologies. This work intends to study the mixed mortar’s mechanical and durability properties, according to effects of variation of constituent elements (cement, hydraulic lime and sand) through the simplex network method. Water consumption, entrained air, compressive strength, flexural tensile strength, pull off strength, elasticity modulus, water absorption index, porosity, density and cracks were evaluated. The results showed that the excessive cement content enhances some mechanical properties, however it reduces the durability because of cracks and detaching. The hydraulic lime and the aggregate in excess tend to reduce the pull off strength and the durability because of the powder behavior of the mortar. This study evidences that it is necessary to define the adequate components proportion focusing in pull of strength and durability indicators.
Construction and Building Materials, 2020
Abstract The mortar behavior depends on the rheological characteristics, and the interaction and ... more Abstract The mortar behavior depends on the rheological characteristics, and the interaction and proportion between its components, which can affect mechanical and durability properties, and also can generate pathologies. This work intends to study the mixed mortar’s mechanical and durability properties, according to effects of variation of constituent elements (cement, hydraulic lime and sand) through the simplex network method. Water consumption, entrained air, compressive strength, flexural tensile strength, pull off strength, elasticity modulus, water absorption index, porosity, density and cracks were evaluated. The results showed that the excessive cement content enhances some mechanical properties, however it reduces the durability because of cracks and detaching. The hydraulic lime and the aggregate in excess tend to reduce the pull off strength and the durability because of the powder behavior of the mortar. This study evidences that it is necessary to define the adequate components proportion focusing in pull of strength and durability indicators.
The Journal of Engineering and Exact Sciences, 2017
Os concretos tradicionais estão evoluindo tecnologicamente, fruto da pesquisa aplicada e resultad... more Os concretos tradicionais estão evoluindo tecnologicamente, fruto da pesquisa aplicada e resultado da introdução conjunta, no elenco das matérias primas básicas do concreto, de adições minerais e aditivos químicos, proporcionando Concreto de Alta Resistência (CAR) e Concreto de Alto Desempenho (CAD). A sílica ativa, um dos materiais cimentícios suplementares mais utilizados na confecção do CAR e do CAD, é um subproduto da fabricação de silício metálico, das ligas de ferrosilício e de outras ligas de silício. Este presente trabalho apresenta caracterização do subproduto (sílica ativa) em relação à sua morfologia, análise química qualitativa, resultados para determinar a influência no comportamento deste material como adição mineral na propriedade mecânica de resistência à compressão axial, trabalhabilidade e acabamento no concreto, a fim de tornar a indústria da construção em concreto mais sustentável. Trata-se de um estudo experimental, exploratório, descritivo e análise quantitativ...
Journal of Materials in Civil Engineering, 2017
AbstractCement pastes and mortars were prepared incorporating carbon nanotubes (CNTs) and nanofib... more AbstractCement pastes and mortars were prepared incorporating carbon nanotubes (CNTs) and nanofibers (CNFs) synthesized directly on ground clinker and silica fume. Setting times of the cement paste...
Increasing the durability of buildings is one of the biggest challenges of the construction indus... more Increasing the durability of buildings is one of the biggest challenges of the construction industry of the 21 century. The problems concerning durability are usually related to the presence of humidity or to water infiltration in the porous cementitious materials used in buildings. Advances in biomimetics have allowed the development of superhydrophobic surfaces and materials, with contact angles greater than 150°, which are able to repel water and aqueous products. In this context, this work summarizes the recent advances on superhydrophobic coatings and admixtures applied to cementitious materials. Recommendations for the future improvement of such products are made. The synthesis of superhydrophobic coatings generally includes the deposition of a low surface energy material (LSEM), especially fluoroalkylsilanes, on a microroughened surface, which, in cementitious materials, is usually achieved with the help of nanoparticles or micrometric molds. In this sense, variables as the s...
Matéria (Rio de Janeiro)
RESUMO O óxido de grafeno tem sido apontado como um material de reforço para compósitos de ciment... more RESUMO O óxido de grafeno tem sido apontado como um material de reforço para compósitos de cimento. Além de ser um material com boa dispersão em água, ele apresenta elevado módulo de elasticidade, elevada resistência à tração, elevada superfície específica e alta condutividade térmica e elétrica. Visando aprofundar o conhecimento acerca do uso do óxido de grafeno em compósitos de cimento, o presente trabalho apresenta uma ampla revisão bibliográfica sobre os efeitos da adição do óxido de grafeno em compósitos de cimento Portland. A metodologia empregada para a seleção dos artigos acadêmicos foi o ProKnow-C, (Knowledge Development Process – Constructivist), ferramenta de revisão literária que permite a evidenciação do estágio atual do conhecimento acadêmico relacionado ao tema de estudo. Por meio desta metodologia de busca e seleção de artigos, foi possível selecionar, a partir de uma amostra bruta de 1354 artigos, os 47 artigos mais relevantes que apresentam as alterações nas propri...
Materials
Cement composites prepared with nanoparticles have been widely studied in order to achieve superi... more Cement composites prepared with nanoparticles have been widely studied in order to achieve superior performance structures. The incorporation of carbon nanotubes (CNTs) is an excellent alternative due to their mechanical, electrical, and thermal properties. However, effective dispersion is essential to ensure strength gains. In the present work, cement pastes were prepared incorporating CNTs in proportions up to 0.10% by weight of cement, dispersed on the surface of anhydrous cement particles in isopropanol suspension and using ultrasonic agitation. Digital image correlation was employed to obtain basic mechanical parameters of three-point bending tests. The results indicated a 34% gain in compressive strength and 12% in flexural tensile strength gains, respectively, as well as a 70% gain in fracture energy and 14% in fracture toughness in the presence of 0.05% CNTs were recorded. These results suggest that CNTs act as crack propagation controllers. Moreover, CNT presence contribute...
Proceedings of the 4th Brazilian Conference on Composite Materials
Due to the necessity to improve the mechanical properties of cement-based materials, carbon nanot... more Due to the necessity to improve the mechanical properties of cement-based materials, carbon nanotubes (CNTs) have been studied to prepare cement composites. Once they present high tensile strength, if well dispersed and well adhered to the cement hydration products, they can improve the mechanical properties of a cement paste system. Because of that, an effective dispersion process is crucial. Studies involving CNTs dispersion in cement particles in presence of a non-aqueous media of isopropanol resulted in improvements in mechanical properties suggesting a good dispersion and strong bond between CNTs and cement particles. Considering that, the present paper analysed a cement paste reinforced with 0%, 0.05% and 0.10% of CNTs dispersed in a non-aqueous media of isopropanol through three-point bending tests in notched specimens and direct tensile tests. The influence of CNTs on the material fracture energy, flexural strength, and tensile strength was addressed. The results pointed out an improvement of 90% of fracture energy in composites with 0.05% of CNTs. The results of direct tensile tests indicate an improvement of about 20% tensile strength in cement paste with 0.05% of CNTs and images by scanning electron microscopy indicate a better dispersion by this proportion. These results suggest not only an effective dispersion of CNTs in cement matrix by the used dispersion methodology at a dosage of 0.05% of CNTs, but also that the cement composites properties may be improved by the presence of them.
Architecture, Civil Engineering, Environment
Carbon nanotubes (CNTs) are hollow tubular channels, formed by graphene laminated sheets. They ca... more Carbon nanotubes (CNTs) are hollow tubular channels, formed by graphene laminated sheets. They can be classified as single-walled (SWCNTs) when they have a simple cylindrical layer of graphene or as multiple-walled (MWCNTs) formed by the joining of two or more single cylindrical layers. Due to the extraordinary properties, as a high tensile strength, the incorporation of the CNTs in civil construction materials has been studied. Recent research has shown that the incorporation of this nanomaterial allows improvements in the mechanical properties of cementitious compounds [1-5]. However, the hydrophobic nature of CNTs makes the dispersion a
Journal of Petroleum Science and Engineering, 2014
ABSTRACT This paper analyzes the influence of carbon nanotubes (CNTs) on the rheological and mech... more ABSTRACT This paper analyzes the influence of carbon nanotubes (CNTs) on the rheological and mechanical properties of cement slurries used in oil wells. CNTs were grown directly onto the cement clinker by chemical vapor deposition. Cement pastes containing 0.1% and 0.3% of CNT bwoc were compared with CNT-free slurries. Lignosulfonate (0.2% bwoc) was used as dispersant in all cement slurries. Compressive and tensile strength were evaluated at the ages of 48 h and 7 days. The results show that the addition of CNTs does not alter the rheological behavior and stability of the cement slurries considering the dispersant and concentrations employed. On the other hand, the presence of CNTs in the cement slurries increases the tensile strength by approximately 15% at 48 h and 7 days of aging for 0.1% CNT bwoc.
Seminário de Discentes dos Programas de Pós-Graduação Stricto Sensu, Sep 5, 2018
Lecture Notes in Civil Engineering, 2021
À minha esposa Priscila, pelo amor e apoio mesmo nos momentos difíceis, pessoa sem a qual eu nunc... more À minha esposa Priscila, pelo amor e apoio mesmo nos momentos difíceis, pessoa sem a qual eu nunca teria chegado ao Brasil e nem teria entrado no "mundo da pesquisa". Ao meu orientador Prof. Dr. José Marcio Fonseca Calixto, por ter acreditado em mim, pela paciência, apoio e pelo carinho e amizade durante estes quatro anos. Ao meu co-orientador Prof. Dr. Luiz Orlando Ladeira, pela atenção e motivação, fazendo com que eu me envolvesse no "universo nano".
Os concretos de ultra-alto desempenho (CUAD) sao materiais a base de cimento que apresentam resis... more Os concretos de ultra-alto desempenho (CUAD) sao materiais a base de cimento que apresentam resistencia a compressao superior a 150 MPa, suas propriedades mecânicas e de durabilidade se apresentam superiores se comparadas aos concretos de alto desempenho e aos concretos convencionais Estudos recentes indicam que a incorporacao de nanotubos de carbono como reforco da matriz de CUAD pode resultar na melhoria de sua microestrutura e consequentemente, melhorar a sua durabilidade frente a ataques como a carbonatacao e a penetracao de ions de cloreto. A presente pesquisa tem por objetivo delinear o estado da arte em torno da durabilidade de CUAD com matriz reforcada com nanotubos de carbono, principalmente sobre o fenomeno da carbonatacao. Nesse sentido utilizou-se o metodo Proknow-C, um processo estruturado para selecao e analise de referencias bibliograficas; atraves do qual construiu-se um portfolio de artigos que foram analisados. Os resultados da pesquisa evidenciam que ainda ha lacu...
Construction and Building Materials, 2020
Abstract Ultra High Performance Concretes (UHPC) are known for exceptional mechanical and durabil... more Abstract Ultra High Performance Concretes (UHPC) are known for exceptional mechanical and durability properties due to optimized particle packing and a denser microstructure. However, the very tight packing of particles resulting in a dense microstructure can be a cause of problems in UHPCs when exposed to higher temperatures. The low porosity delays the movement of water vapour inside de concrete and a layer of condensed water is created, preventing water to escape the microstructure and increasing internal pressure, that may result in explosive spalling. In this research, carbon nanotubes (CNTs) were introduced in UHPCs to assess their influence on the properties after exposition to high temperatures. Specimens were subjected to slow and fast heating rates and occurrence of spalling was investigated. Mechanical tests, such as compressive strength (before heating and after heating) and splitting tensile strength were conducted to investigate the impact of CNTs on the mechanical properties. Gas permeability tests were performed to investigate alterations in porosity due to the presence of CNTs. Results show that the presence of CNTs can reduce the occurrence of spalling at additions of 0.05% and 0.10% by weight of cement. CNTs can also increase the residual strength at temperatures up to 300 °C at a slow heating rate. At the same time, the 28-day compressive and splitting tensile strengths remained unaltered and oxygen permeability coefficients were reduced when CNTs were added to the matrix.
Seminário de Discentes dos Programas de Pós-Graduação Stricto Sensu, Sep 5, 2018
Lecture Notes in Civil Engineering, 2021
À minha esposa Priscila, pelo amor e apoio mesmo nos momentos difíceis, pessoa sem a qual eu nunc... more À minha esposa Priscila, pelo amor e apoio mesmo nos momentos difíceis, pessoa sem a qual eu nunca teria chegado ao Brasil e nem teria entrado no "mundo da pesquisa". Ao meu orientador Prof. Dr. José Marcio Fonseca Calixto, por ter acreditado em mim, pela paciência, apoio e pelo carinho e amizade durante estes quatro anos. Ao meu co-orientador Prof. Dr. Luiz Orlando Ladeira, pela atenção e motivação, fazendo com que eu me envolvesse no "universo nano".
Os concretos de ultra-alto desempenho (CUAD) sao materiais a base de cimento que apresentam resis... more Os concretos de ultra-alto desempenho (CUAD) sao materiais a base de cimento que apresentam resistencia a compressao superior a 150 MPa, suas propriedades mecânicas e de durabilidade se apresentam superiores se comparadas aos concretos de alto desempenho e aos concretos convencionais Estudos recentes indicam que a incorporacao de nanotubos de carbono como reforco da matriz de CUAD pode resultar na melhoria de sua microestrutura e consequentemente, melhorar a sua durabilidade frente a ataques como a carbonatacao e a penetracao de ions de cloreto. A presente pesquisa tem por objetivo delinear o estado da arte em torno da durabilidade de CUAD com matriz reforcada com nanotubos de carbono, principalmente sobre o fenomeno da carbonatacao. Nesse sentido utilizou-se o metodo Proknow-C, um processo estruturado para selecao e analise de referencias bibliograficas; atraves do qual construiu-se um portfolio de artigos que foram analisados. Os resultados da pesquisa evidenciam que ainda ha lacu...
Construction and Building Materials, 2020
Abstract Ultra High Performance Concretes (UHPC) are known for exceptional mechanical and durabil... more Abstract Ultra High Performance Concretes (UHPC) are known for exceptional mechanical and durability properties due to optimized particle packing and a denser microstructure. However, the very tight packing of particles resulting in a dense microstructure can be a cause of problems in UHPCs when exposed to higher temperatures. The low porosity delays the movement of water vapour inside de concrete and a layer of condensed water is created, preventing water to escape the microstructure and increasing internal pressure, that may result in explosive spalling. In this research, carbon nanotubes (CNTs) were introduced in UHPCs to assess their influence on the properties after exposition to high temperatures. Specimens were subjected to slow and fast heating rates and occurrence of spalling was investigated. Mechanical tests, such as compressive strength (before heating and after heating) and splitting tensile strength were conducted to investigate the impact of CNTs on the mechanical properties. Gas permeability tests were performed to investigate alterations in porosity due to the presence of CNTs. Results show that the presence of CNTs can reduce the occurrence of spalling at additions of 0.05% and 0.10% by weight of cement. CNTs can also increase the residual strength at temperatures up to 300 °C at a slow heating rate. At the same time, the 28-day compressive and splitting tensile strengths remained unaltered and oxygen permeability coefficients were reduced when CNTs were added to the matrix.
Construction and Building Materials, 2020
Abstract The mortar behavior depends on the rheological characteristics, and the interaction and ... more Abstract The mortar behavior depends on the rheological characteristics, and the interaction and proportion between its components, which can affect mechanical and durability properties, and also can generate pathologies. This work intends to study the mixed mortar’s mechanical and durability properties, according to effects of variation of constituent elements (cement, hydraulic lime and sand) through the simplex network method. Water consumption, entrained air, compressive strength, flexural tensile strength, pull off strength, elasticity modulus, water absorption index, porosity, density and cracks were evaluated. The results showed that the excessive cement content enhances some mechanical properties, however it reduces the durability because of cracks and detaching. The hydraulic lime and the aggregate in excess tend to reduce the pull off strength and the durability because of the powder behavior of the mortar. This study evidences that it is necessary to define the adequate components proportion focusing in pull of strength and durability indicators.
Construction and Building Materials, 2020
Abstract The mortar behavior depends on the rheological characteristics, and the interaction and ... more Abstract The mortar behavior depends on the rheological characteristics, and the interaction and proportion between its components, which can affect mechanical and durability properties, and also can generate pathologies. This work intends to study the mixed mortar’s mechanical and durability properties, according to effects of variation of constituent elements (cement, hydraulic lime and sand) through the simplex network method. Water consumption, entrained air, compressive strength, flexural tensile strength, pull off strength, elasticity modulus, water absorption index, porosity, density and cracks were evaluated. The results showed that the excessive cement content enhances some mechanical properties, however it reduces the durability because of cracks and detaching. The hydraulic lime and the aggregate in excess tend to reduce the pull off strength and the durability because of the powder behavior of the mortar. This study evidences that it is necessary to define the adequate components proportion focusing in pull of strength and durability indicators.
The Journal of Engineering and Exact Sciences, 2017
Os concretos tradicionais estão evoluindo tecnologicamente, fruto da pesquisa aplicada e resultad... more Os concretos tradicionais estão evoluindo tecnologicamente, fruto da pesquisa aplicada e resultado da introdução conjunta, no elenco das matérias primas básicas do concreto, de adições minerais e aditivos químicos, proporcionando Concreto de Alta Resistência (CAR) e Concreto de Alto Desempenho (CAD). A sílica ativa, um dos materiais cimentícios suplementares mais utilizados na confecção do CAR e do CAD, é um subproduto da fabricação de silício metálico, das ligas de ferrosilício e de outras ligas de silício. Este presente trabalho apresenta caracterização do subproduto (sílica ativa) em relação à sua morfologia, análise química qualitativa, resultados para determinar a influência no comportamento deste material como adição mineral na propriedade mecânica de resistência à compressão axial, trabalhabilidade e acabamento no concreto, a fim de tornar a indústria da construção em concreto mais sustentável. Trata-se de um estudo experimental, exploratório, descritivo e análise quantitativ...
Journal of Materials in Civil Engineering, 2017
AbstractCement pastes and mortars were prepared incorporating carbon nanotubes (CNTs) and nanofib... more AbstractCement pastes and mortars were prepared incorporating carbon nanotubes (CNTs) and nanofibers (CNFs) synthesized directly on ground clinker and silica fume. Setting times of the cement paste...
Increasing the durability of buildings is one of the biggest challenges of the construction indus... more Increasing the durability of buildings is one of the biggest challenges of the construction industry of the 21 century. The problems concerning durability are usually related to the presence of humidity or to water infiltration in the porous cementitious materials used in buildings. Advances in biomimetics have allowed the development of superhydrophobic surfaces and materials, with contact angles greater than 150°, which are able to repel water and aqueous products. In this context, this work summarizes the recent advances on superhydrophobic coatings and admixtures applied to cementitious materials. Recommendations for the future improvement of such products are made. The synthesis of superhydrophobic coatings generally includes the deposition of a low surface energy material (LSEM), especially fluoroalkylsilanes, on a microroughened surface, which, in cementitious materials, is usually achieved with the help of nanoparticles or micrometric molds. In this sense, variables as the s...
Matéria (Rio de Janeiro)
RESUMO O óxido de grafeno tem sido apontado como um material de reforço para compósitos de ciment... more RESUMO O óxido de grafeno tem sido apontado como um material de reforço para compósitos de cimento. Além de ser um material com boa dispersão em água, ele apresenta elevado módulo de elasticidade, elevada resistência à tração, elevada superfície específica e alta condutividade térmica e elétrica. Visando aprofundar o conhecimento acerca do uso do óxido de grafeno em compósitos de cimento, o presente trabalho apresenta uma ampla revisão bibliográfica sobre os efeitos da adição do óxido de grafeno em compósitos de cimento Portland. A metodologia empregada para a seleção dos artigos acadêmicos foi o ProKnow-C, (Knowledge Development Process – Constructivist), ferramenta de revisão literária que permite a evidenciação do estágio atual do conhecimento acadêmico relacionado ao tema de estudo. Por meio desta metodologia de busca e seleção de artigos, foi possível selecionar, a partir de uma amostra bruta de 1354 artigos, os 47 artigos mais relevantes que apresentam as alterações nas propri...
Materials
Cement composites prepared with nanoparticles have been widely studied in order to achieve superi... more Cement composites prepared with nanoparticles have been widely studied in order to achieve superior performance structures. The incorporation of carbon nanotubes (CNTs) is an excellent alternative due to their mechanical, electrical, and thermal properties. However, effective dispersion is essential to ensure strength gains. In the present work, cement pastes were prepared incorporating CNTs in proportions up to 0.10% by weight of cement, dispersed on the surface of anhydrous cement particles in isopropanol suspension and using ultrasonic agitation. Digital image correlation was employed to obtain basic mechanical parameters of three-point bending tests. The results indicated a 34% gain in compressive strength and 12% in flexural tensile strength gains, respectively, as well as a 70% gain in fracture energy and 14% in fracture toughness in the presence of 0.05% CNTs were recorded. These results suggest that CNTs act as crack propagation controllers. Moreover, CNT presence contribute...
Proceedings of the 4th Brazilian Conference on Composite Materials
Due to the necessity to improve the mechanical properties of cement-based materials, carbon nanot... more Due to the necessity to improve the mechanical properties of cement-based materials, carbon nanotubes (CNTs) have been studied to prepare cement composites. Once they present high tensile strength, if well dispersed and well adhered to the cement hydration products, they can improve the mechanical properties of a cement paste system. Because of that, an effective dispersion process is crucial. Studies involving CNTs dispersion in cement particles in presence of a non-aqueous media of isopropanol resulted in improvements in mechanical properties suggesting a good dispersion and strong bond between CNTs and cement particles. Considering that, the present paper analysed a cement paste reinforced with 0%, 0.05% and 0.10% of CNTs dispersed in a non-aqueous media of isopropanol through three-point bending tests in notched specimens and direct tensile tests. The influence of CNTs on the material fracture energy, flexural strength, and tensile strength was addressed. The results pointed out an improvement of 90% of fracture energy in composites with 0.05% of CNTs. The results of direct tensile tests indicate an improvement of about 20% tensile strength in cement paste with 0.05% of CNTs and images by scanning electron microscopy indicate a better dispersion by this proportion. These results suggest not only an effective dispersion of CNTs in cement matrix by the used dispersion methodology at a dosage of 0.05% of CNTs, but also that the cement composites properties may be improved by the presence of them.
Architecture, Civil Engineering, Environment
Carbon nanotubes (CNTs) are hollow tubular channels, formed by graphene laminated sheets. They ca... more Carbon nanotubes (CNTs) are hollow tubular channels, formed by graphene laminated sheets. They can be classified as single-walled (SWCNTs) when they have a simple cylindrical layer of graphene or as multiple-walled (MWCNTs) formed by the joining of two or more single cylindrical layers. Due to the extraordinary properties, as a high tensile strength, the incorporation of the CNTs in civil construction materials has been studied. Recent research has shown that the incorporation of this nanomaterial allows improvements in the mechanical properties of cementitious compounds [1-5]. However, the hydrophobic nature of CNTs makes the dispersion a
Journal of Petroleum Science and Engineering, 2014
ABSTRACT This paper analyzes the influence of carbon nanotubes (CNTs) on the rheological and mech... more ABSTRACT This paper analyzes the influence of carbon nanotubes (CNTs) on the rheological and mechanical properties of cement slurries used in oil wells. CNTs were grown directly onto the cement clinker by chemical vapor deposition. Cement pastes containing 0.1% and 0.3% of CNT bwoc were compared with CNT-free slurries. Lignosulfonate (0.2% bwoc) was used as dispersant in all cement slurries. Compressive and tensile strength were evaluated at the ages of 48 h and 7 days. The results show that the addition of CNTs does not alter the rheological behavior and stability of the cement slurries considering the dispersant and concentrations employed. On the other hand, the presence of CNTs in the cement slurries increases the tensile strength by approximately 15% at 48 h and 7 days of aging for 0.1% CNT bwoc.