Study of thermal conductivity in mass concrete with polypropylene and steel fibers

Thermal conductivity is the physical property of materials that measures their capacity to transfer heat by conduction, increased with increasing saturation, temperature, volumetric fraction and thermal conductivity of the aggregate and decreasing with the increase of the relation w / C. This property influences aspects as important as the fire behavior of reinforced concrete structures. On the other hand, the incorporation of polypropylene fibers, due to its physical, chemical and mechanical characteristics, improves its resistance and controls the cracking while the incorporation of steel fibers, modifies the nonlinear behavior of the structural concrete, especially in tensile, delaying the propagation of cracks and increasing their ductility. Based on the above premises, the objective of the present study is to compare the thermal conductivity of different concretes, without addition and with additions of polypropylene fibers and steel fibers in different percentages by weight of cement

Analysis of fire resistance of concrete with polypropylene or steel fibers

The decrease in concrete resistance and the expansion generated in reinforced concrete structures by direct exposure to fire at 400 degrees C maximum temperature serves as the basis for the present research. The aim is to improve these problems by the addition of steel fibers or of polypropylene fibers in concrete. From the results analysis of compression fracture tests on cylindrical concrete specimens, it can be concluded that concrete with addition of polypropylene fibers or steel fibers are a good alternative to traditional concrete, because both its strength, and its behavior in case of fire are improved, delaying the appearance of fissures and explosive concrete spalling

Estudio del comportamiento frente al fuego del hormigón en masa con adición de nanofibras de carbono (CNFS) y su comparación con hormigones sin adición y con otras adiciones

En la actualidad la nanotecnología apunta a ser la herramienta que a corto plazo generará los nuevos adelantos en ingeniería y por ende será el principal motor del desarrollo de la sociedad. Los nanomateriales están ofreciendo importantes mejoras en el desarrollo de la tecnología, por ello, conocer su interacción con el hormigón frente a la acción de un incendio resulta de un importante atractivo. Conocidas las negativas consecuencias que se derivan en los incendios de los edificios, es importante mejorar los materiales que componen el hormigón y así optimizar su comportamiento frente a la agresión térmica, dando lugar a hormigones innovadores con características extremadamente superiores. Desde hace mucho tiempo, la incorporación de fibras en el hormigón ha sido una práctica llevada a cabo para mejorar el comportamiento del hormigón. En los últimos años, se han desarrollado mejoras y alcanzado resultados exitosos del comportamiento frente al fuego en el hormigón con la adición de fibras. Sin embargo, la aplicación de la nanotecnología en el hormigón frente a la acción de un fuego real no está experimentado. Por ello, y partiendo de estas premisas, en el presente trabajo de investigación se ha llevado a cabo el estudio del comportamiento frente al fuego del hormigón en masa con adición de nanofibras de carbono (CNFs) y su comparación con hormigones sin adición, con adiciones de fibras de polipropileno y de acero, e hibridación de CNFs con fibras polipropileno y de acero. Para ello, se han elaborado probetas de hormigón con las diferentes adiciones y porcentajes de adición, y se han sometido a los ensayos de exposición a fuego real, de resistencia a compresión, de conductividad térmica y del análisis microscópico. A partir del análisis de resultados, se puede concluir, que la adición de CNFs en el hormigón tradicional revierte en una mejora del efecto “spalling” y del comportamiento mecánico del hormigón frente al fuego, con un aumento de la ductilidad. Permite realizar diseños de hormigones con conductividades térmicas concretas en función de las necesidades existentes. Por otro lado, hay que destacar que los hormigones con adición hibridada de CNFs y fibras, presentan mayores resistencias y una mejor ductilidad después de una exposición al fuego, dando lugar a un mejor comportamiento mecánico del hormigón. De la misma manera sucede en hormigones con adición de fibras de polipropileno y fibras de acero, donde los resultados a cerca de las características mecánicas son altamente satisfactorios, convirtiéndose en una optimización del hormigón. Por tanto, el empleo de adición de nanofibras de carbono (CNFs) en el proceso de fabricación del hormigón, así como del uso de fibras e hibridación entre ellas, se convierte en una práctica que presenta ventajas competitivas respecto a las técnicas de construcción convencionales, siendo una buena alternativa al hormigón tradicional.At present, nanotechnology aims to be a tool for the generation of advance in engineering, and it is therefore an important factor for the development of society. Nanomaterials are contributing substantially to the making of new technologies, for that reason, to know their interaction with concrete and its reaction to fire is very important. The negative consequences that result from the effect of fire in buildings impose the need to upgrade the properties of materials in the face of thermal aggression. High performance concrete appears to be the best choice. For a long time, the incorporation of fibers in concrete has often been used to improve the behavior of this material. In recent years, improvements have been made and successful results of fire behavior in concrete with the addition of fibers have been obtained. However, the application of nanotechnology in concrete against the action of actual fire has not been properly tested yet. Based on these premises, in the present research work we have carried out the study of the behavior against fire of mass concrete with addition of carbon nanofibers (CNFs) and its comparison with concrete without addition, with additions of polypropylene and steel fibers, and hybridization of CNFs with polypropylene and steel fibers. To this purpose, concrete specimens with the different additions and addition percentages have been prepared, and have been subjected to the tests of exposure to fire, compression resistance, thermal conductivity and microscopic analysis. From the analysis of results, it can be concluded that the addition of CNFs in traditional concrete results in reduction of the "spalling" effect and also in an increase the mechanical behavior of the concrete against fire, with an upgrade in ductility. Additionally, it allows to produce concrete designs with concrete thermal conductivities according to the existing needs. On the other hand, it should be noted that concrete with hybridized addition of CNFs and fibers shows higher resistance and better ductility after an exposure to fire, giving rise to a better mechanical behavior of the concrete. A similar case is found in concrete with addition of polypropylene fibers and steel fibers, where the results of the mechanical characteristics are highly satisfactory, showing a clear upgrade of the concrete under study. In short, the addition of carbon nanofibers (CNFs) during the concrete manufacturing process, as well as the use of fibers and hybridization between them, becomes a practice that yields competitive results with respect to conventional construction techniques, being a good alternative to traditional concrete

Estudio del comportamiento frente al fuego del hormigón en masa con adición de nanofibras de carbono (CNFS) y su comparación con hormigones sin adición y con otras adiciones

En la actualidad la nanotecnología apunta a ser la herramienta que a corto plazo generará los nuevos adelantos en ingeniería y por ende será el principal motor del desarrollo de la sociedad. Los nanomateriales están ofreciendo importantes mejoras en el desarrollo de la tecnología, por ello, conocer su interacción con el hormigón frente a la acción de un incendio resulta de un importante atractivo. Conocidas las negativas consecuencias que se derivan en los incendios de los edificios, es importante mejorar los materiales que componen el hormigón y así optimizar su comportamiento frente a la agresión térmica, dando lugar a hormigones innovadores con características extremadamente superiores. Desde hace mucho tiempo, la incorporación de fibras en el hormigón ha sido una práctica llevada a cabo para mejorar el comportamiento del hormigón. En los últimos años, se han desarrollado mejoras y alcanzado resultados exitosos del comportamiento frente al fuego en el hormigón con la adición de fibras. Sin embargo, la aplicación de la nanotecnología en el hormigón frente a la acción de un fuego real no está experimentado. Por ello, y partiendo de estas premisas, en el presente trabajo de investigación se ha llevado a cabo el estudio del comportamiento frente al fuego del hormigón en masa con adición de nanofibras de carbono (CNFs) y su comparación con hormigones sin adición, con adiciones de fibras de polipropileno y de acero, e hibridación de CNFs con fibras polipropileno y de acero. Para ello, se han elaborado probetas de hormigón con las diferentes adiciones y porcentajes de adición, y se han sometido a los ensayos de exposición a fuego real, de resistencia a compresión, de conductividad térmica y del análisis microscópico. A partir del análisis de resultados, se puede concluir, que la adición de CNFs en el hormigón tradicional revierte en una mejora del efecto “spalling” y del comportamiento mecánico del hormigón frente al fuego, con un aumento de la ductilidad. Permite realizar diseños de hormigones con conductividades térmicas concretas en función de las necesidades existentes. Por otro lado, hay que destacar que los hormigones con adición hibridada de CNFs y fibras, presentan mayores resistencias y una mejor ductilidad después de una exposición al fuego, dando lugar a un mejor comportamiento mecánico del hormigón. De la misma manera sucede en hormigones con adición de fibras de polipropileno y fibras de acero, donde los resultados a cerca de las características mecánicas son altamente satisfactorios, convirtiéndose en una optimización del hormigón. Por tanto, el empleo de adición de nanofibras de carbono (CNFs) en el proceso de fabricación del hormigón, así como del uso de fibras e hibridación entre ellas, se convierte en una práctica que presenta ventajas competitivas respecto a las técnicas de construcción convencionales, siendo una buena alternativa al hormigón tradicional. ----------ABSTRACT---------- At present, nanotechnology aims to be a tool for the generation of advance in engineering, and it is therefore an important factor for the development of society. Nanomaterials are contributing substantially to the making of new technologies, for that reason, to know their interaction with concrete and its reaction to fire is very important. The negative consequences that result from the effect of fire in buildings impose the need to upgrade the properties of materials in the face of thermal aggression. High performance concrete appears to be the best choice. For a long time, the incorporation of fibers in concrete has often been used to improve the behavior of this material. In recent years, improvements have been made and successful results of fire behavior in concrete with the addition of fibers have been obtained. However, the application of nanotechnology in concrete against the action of actual fire has not been properly tested yet. Based on these premises, in the present research work we have carried out the study of the behavior against fire of mass concrete with addition of carbon nanofibers (CNFs) and its comparison with concrete without addition, with additions of polypropylene and steel fibers, and hybridization of CNFs with polypropylene and steel fibers. To this purpose, concrete specimens with the different additions and addition percentages have been prepared, and have been subjected to the tests of exposure to fire, compression resistance, thermal conductivity and microscopic analysis. From the analysis of results, it can be concluded that the addition of CNFs in traditional concrete results in reduction of the "spalling" effect and also in an increase the mechanical behavior of the concrete against fire, with an upgrade in ductility. Additionally, it allows to produce concrete designs with concrete thermal conductivities according to the existing needs. On the other hand, it should be noted that concrete with hybridized addition of CNFs and fibers shows higher resistance and better ductility after an exposure to fire, giving rise to a better mechanical behavior of the concrete. A similar case is found in concrete with addition of polypropylene fibers and steel fibers, where the results of the mechanical characteristics are highly satisfactory, showing a clear upgrade of the concrete under study. In short, the addition of carbon nanofibers (CNFs) during the concrete manufacturing process, as well as the use of fibers and hybridization between them, becomes a practice that yields competitive results with respect to conventional construction techniques, being a good alternative to traditional concrete

Study of thermal conductivity in mass concrete with polypropylene and steel fibers

Thermal conductivity is the physical property of materials that measures their capacity to transfer heat by conduction, increased with increasing saturation, temperature, volumetric fraction and thermal conductivity of the aggregate and decreasing with the increase of the relation w / C. This property influences aspects as important as the fire behavior of reinforced concrete structures. On the other hand, the incorporation of polypropylene fibers, due to its physical, chemical and mechanical characteristics, improves its resistance and controls the cracking while the incorporation of steel fibers, modifies the nonlinear behavior of the structural concrete, especially in tensile, delaying the propagation of cracks and increasing their ductility. Based on the above premises, the objective of the present study is to compare the thermal conductivity of different concretes, without addition and with additions of polypropylene fibers and steel fibers in different percentages by weight of cement

Analysis of behavior of concrete with hybridization of polypropylene fibers and carbon nanofibers (CNFs)

It is clear, the great impact that the latest advances in the field of nanomaterials is having in the scientific community The possibilities of graphene and its derivatives are endless, since it has qualities never found before in another material, such as better electrical conductivity that of copper, and a resistance and flexibility between 100 and 300 times greater than steel. Although carbon nanofibers (CNFs) are used mainly in the field of technology, research is beginning to study the behavior of concretes with CNFs and that they show a better resistance to flexion, an increase in ductility, a better control of microcracks. and an improvement in compression resistance at early ages, while the incorporation of polypropylene fibers into concrete is a well-known result. The objective of the present investigation is to study the mechanical compression behavior in concrete with hybridization of fibers and compare it with traditional concretes. For this, cylindrical concrete specimens were made with hybridization of carbon nanofibers (CNFs) and polypropylene fibers, with 1% by weight of cement of each type of addition and cylindrical concrete specimens without additions, according to the results obtained it can be seen that the hybridization of the fibers does not represent a great advantage in the compression strength of the concrete, but it implies an improvement in the ductility of the same

Behavior resulting from fire in plasterboard with plastic cable waste aggregates

This article analyzes the effect of fire on plasterboards with aggregates of plastic cable waste, considering the plaster coating as a strategy to reduce the flammability of the added polymers. A real test was performed, using a direct fire set in a Madrid fire station, and a theoretical estimate of the composition of the gas emissions, focused in CO2 and CO, during a fire in a type room is presented. The results reflect that there is no clear trend between the evolution of temperatures over time and the amount of plastic waste added to the plaster matrix in the different specimens, but a different behavior is obtained depending on the surroundings where they are located. Temperatures of 600 °C are reached between 5 and 10 min after the start of the fire if they are located in a place with heat containment, and they do not reach 400 °C in the same period of time in a place with less heat containment. It was also observed that gypsum can be considered a passive protection of polymers, as it retards the effect of the flame on them. Concerning the gases released, the theoretical calculations, based on the elemental and thermogravimetric analysis of the plastic cable waste, reveal that the amount of carbon dioxide generated in a fire would not pose a risk to people's health whereas the values obtained for the carbon monoxide exceed the limited considered dangerous to health for a period greater than 15 min. Using plastic cable waste as secondary raw material reduces the number of incinerations to be carried out in landfills with this type of waste, thereby decreasing the potential emission of contaminants into the atmosphere and contributing to the sustainability of our planet. © 2021 Elsevier Lt

Analysis of fire resistance of cement mortars with mineral wool from recycling

The objective of this research is to analyse the fire resistance of cement mortars with mineral wool from construction and demolition waste (CDW) recycling. The recycled mortars are therefore exposed to direct fire reaching a maximum temperature of 700 °C, and an experimental plan is designed to analyse thermo-mechanical behaviour before and after the testing of the mortars with different types of recycled fibres. The results show that the surface hardness of all mortars is practically unchanged after the fire, whereas the incorporation of fibre residues produce a significant improvement in the flexural strength after fire test compared with the reference mortar. The compressive strength values of all mortars decrease after the fire although they remain at optimum values for use according to regulatory requirements. The values of thermal conductivity are lower or remain unchanged after the fire test. Results show that the addition of these recycled fibres can be a sustainable alternative to the commercial ones currently being used, improving mechanical-thermal behaviour after the fire and preventing the explosive behaviour of the mortars. © 2020 Elsevier Lt

Behavior resulting from fire in plasterboard with plastic cable waste aggregates

This article analyzes the effect of fire on plasterboards with aggregates of plastic cable waste, considering the plaster coating as a strategy to reduce the flammability of the added polymers. A real test was performed, using a direct fire set in a Madrid fire station, and a theoretical estimate of the composition of the gas emissions, focused in CO2 and CO, during a fire in a type room is presented. The results reflect that there is no clear trend between the evolution of temperatures over time and the amount of plastic waste added to the plaster matrix in the different specimens, but a different behavior is obtained depending on the surroundings where they are located. Temperatures of 600 °C are reached between 5 and 10 min after the start of the fire if they are located in a place with heat containment, and they do not reach 400 °C in the same period of time in a place with less heat containment. It was also observed that gypsum can be considered a passive protection of polymers, as it retards the effect of the flame on them. Concerning the gases released, the theoretical calculations, based on the elemental and thermogravimetric analysis of the plastic cable waste, reveal that the amount of carbon dioxide generated in a fire would not pose a risk to people's health whereas the values obtained for the carbon monoxide exceed the limited considered dangerous to health for a period greater than 15 min. Using plastic cable waste as secondary raw material reduces the number of incinerations to be carried out in landfills with this type of waste, thereby decreasing the potential emission of contaminants into the atmosphere and contributing to the sustainability of our planet. © 2021 Elsevier Lt

Analysis of the Behavior of Mass Concrete with the Addition of Carbon Nanofibers (CNFs) When Exposed to Fire

Due to the importance of concrete as a structural material and the pathologies that can be achieved by reinforced concrete structures when they are subjected to the action of fire both at the level of resistance and deformation, in this research we study the mechanical behavior of mass concrete with the addition of carbon nanofibers (CNFs) when exposed to the action of fire, in order to determine the improvements that this type of addition produces in concrete. To achieve this objective, compression break tests have been carried out on cylindrical concrete specimens incorporating CNFs. From the analysis of results, it can be concluded that the residual resistant capacity of concrete with the addition of 1% of CNFs by weight of cement subjected to the direct action of fire, is greater than that of concrete without additions, not obtaining better results, if the addition of CNFs increases to 2%. The addition of 1% of CNFs has not influenced the temperatures reached in the concrete, but produces a more homogeneous cooling and that the paste-aggregate bond is maintained despite thermal aggression, which decreases the spalling effect