The Experts below are selected from a list of 9321 Experts worldwide ranked by ideXlab platform
Victor M. Ferreira - One of the best experts on this subject based on the ideXlab platform.
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Microstructure and Hardened State properties on pozzolan-containing concrete
Construction and Building Materials, 2017Co-Authors: H. Paiva, Ana Velosa, António Santos Silva, Paulo Cachim, Victor M. FerreiraAbstract:Abstract The homogeneous State of the concrete in the fresh State has consequences on their properties in the Hardened State. The use of pozzolanic concrete must be carefully evaluated, because the physical and chemical differences of each pozzolan have consequences on concrete Hardened State properties. In this work, two physical and chemically different pozzolans were used to evaluate the effect on concrete microstructure and its basic Hardened State properties. Scanning electron microscopy (SEM) was used and can be an effective tool in the analysis of the microstructure allowing a better understanding of the properties of concrete in Hardened State. It allows showing that the differences in the two pozzolans (metakaolin and diatomite) promote different microstructures as well as different final properties of pozzolanic concrete. Moreover, it was also shown that the use of a water reducing agent, to adjust workability instead of water, promotes an improvement in both the microstructure and the Hardened State features such as porosity and mechanical strength.
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Biomass fly ash effect on fresh and Hardened State properties of cement based materials
Composites Part B: Engineering, 2015Co-Authors: Rejini Rajamma, L Senff, João A. Labrincha, M.j. Ribeiro, Richard J Ball, Geoffrey C. Allen, Victor M. FerreiraAbstract:Cement pastes and mortars were prepared by replacing ordinary Portland cement with different dosages of biomass fly ashes (0, 10, 20 and 30% BFA) whilst in dry condition. The effect of BFA on the flow behaviour (spread on table and rheology), setting time, temperature of hydration and electrical resistivity was studied in this experimental research. Increasing the amount of BFA in the compositions required extra dosage of water, as a result of particles fineness, tendency for agglomeration and retention/absorption of water molecules. As a consequence, the relative amount of free water diminishes and the flowability is poorer. The introduction of BFA also led to an increase in setting time, while the resistivity obtained from the impedance measurements tends to be lower than the reference paste (ash-free). The higher concentration of mobile species in the pore solution, namely sodium ions introduced by the ash, explains that tendency. The hydration temperature of cement pastes tends to decrease with the level of cement to ash replacement. Between the two tested ashes (from grate and fluidized sand bed furnaces), differences in particle size and shape, in the amount of residual organic matter and concentration of inorganic components define minor changes in the workability and setting behaviour. Therefore, the introduction of biomass fly ashes affects the Hardened State features but do not compromise them.
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Incorporation of titanium dioxide nanoparticles in mortars — Influence of microstructure in the Hardened State properties and photocatalytic activity
Cement and Concrete Research, 2013Co-Authors: S. S. Lucas, Victor M. Ferreira, J. L. Barroso De AguiarAbstract:The environmental pollution in urban areas is one of the causes for poor indoor air quality in buildings, particularly in suburban areas. The development of photocatalytic construction materials can contribute to clean the air and improve sustainability levels. Previous studies have focused mainly in cement and concrete materials, disregarding the potential application in historic buildings. In this work, a photocatalytic additive (titanium dioxide) was added to mortars prepared with aerial lime, cement and gypsum binders. The main goal was to study the way that microstructural changes affect the photocatalytic efficiency. The photocatalytic activity was determined using a reactor developed to assess the degradation rate with a common urban pollutant, NOx. The laboratory results show that all the compositions tested exhibited high photocatalytic efficiency. It was demonstrated that photocatalytic mortars can be applied in new and old buildings, because the nanoadditives do not compromise the mortar Hardened State properties.
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Latent heat storage in PCM containing mortars - study of microstructural modifications
Energy and Buildings, 2013Co-Authors: S. S. Lucas, Victor M. Ferreira, J. L. Barroso De AguiarAbstract:The incorporation of phase change materials (PCM) into traditional mortars give to these products the ability to store and release heat. In this way it is possible to reduce the energy consumption and improve the thermal comfort in buildings. The introduction of micro and nanomaterials in the mortars matrix can cause microstructural changes that need to be addressed in order to optimize the PCM addition. The relationship between the Hardened State performance of different PCM-mortars, its internal microstructure and pore distribution as been observed for different binders such as lime, cement and gypsum. Their Hardened State properties, microstructural modifications and heat storage capabilities were evaluated. The ability to store and release heat depends strongly on the size and distribution of internal pores and not only on the PCM content. Using a thermal efficiency test, an important correlation between thermal performance and the mortars microstructure was established, for mortars with 0–30% of PCM added.
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Energy and Buildings
2013Co-Authors: S. S. Lucas, Victor M. Ferreira, J. L. Barroso De AguiarAbstract:a b s t r a c t The incorporation of phase change materials (PCM) into traditional mortars give to these products the ability to store and release heat. In this way it is possible to reduce the energy consumption and improve the thermal comfort in buildings. The introduction of micro and nanomaterials in the mortars matrix can cause microstructural changes that need to be addressed in order to optimize the PCM addition. The relationship between the Hardened State performance of different PCM-mortars, its internal microstruc- ture and pore distribution as been observed for different binders such as lime, cement and gypsum. Their Hardened State properties, microstructural modifications and heat storage capabilities were evaluated. The ability to store and release heat depends strongly on the size and distribution of internal pores and not only on the PCM content. Using a thermal efficiency test, an important correlation between thermal performance and the mortars microstructure was established, for mortars with 0-30% of PCM added. © 2013 Elsevier B.V. All rights reserved.
Mohamed Boutouil - One of the best experts on this subject based on the ideXlab platform.
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Influence of different surface treatments on the water absorption capacity of flax fibres: Rheology of fresh reinforced-mortars and mechanical properties in the Hardened State
Construction and Building Materials, 2019Co-Authors: Jonathan Page, Fouzia Khadraoui, Moussa Gomina, Mohamed BoutouilAbstract:Abstract An experimental investigation was undertaken on the influence of different surface treatments of flax fibres on mortar properties in both fresh and Hardened States. Three types of coating were explored for surface modification: atmospheric-pressure plasma, mineral coating made of a grout of cement and ground granulated blast-furnace slag, and polymer coating based on linseed oil. Water absorption tests were performed to evaluate the performance of the coatings. Water absorption kinetics and/or water retention capacity were drastically modified by the plasma treatment at atmospheric-pressure and by the linseed oil treatment. The workability of the pastes incorporating fibres coated with the cement grout or linseed oil was greatly improved compared to the raw fibres. The presence of fibres significantly increases the rate of entrapped air, which seems to depend on the nature of the coating. In the Hardened State, regardless of the nature of the fibre coating, the flexural strength increases beyond 90 days of curing. Up to 320 days of curing, the compressive strengths of the different composites are similar to that of the control mortar, except for the composite with linseed oil coated-fibres which proves to be the most porous. The presence of flax fibres also enhances the mortar toughness and prevent from desiccation cracking. Nevertheless, none of the treatments experimented in this work makes it possible to preserve the beneficial effects of fibres on the mechanical behaviour of composites in the long term.
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Multi-physical properties of a structural concrete incorporating short flax fibers
Construction and Building Materials, 2017Co-Authors: Jonathan Page, Fouzia Khadraoui, Mohamed Boutouil, Moussa GominaAbstract:An experimental investigation was undertaken on the physical characterization of a flax fiber-reinforced concrete (FFRC) in both fresh and Hardened State. The objective of this study is to provide guidance for the mix-design of these FFRC. The study was conducted from two points of views improving the workability of the concrete in a fresh State and improving the flexural strength in the Hardened State. Several parameters have been studied independently as fiber length, fiber content, or the paste content. The characterization of flax fibers highlighted a high water absorption capacity which must be taken into account for the concrete mix-design. In addition, the flax fibers significantly impact the compactness of granular skeleton. For the characterization of concrete, testing in the fresh State showed a significant decrease of the workability of concrete with the addition of flax fibers. However, the use of shorter fibers, allows to reduce this damaging influence on the fresh concrete workability. Moreover, increasing the paste content allows compensating this fluidity loss. In the Hardened State, the increase of the fiber content enhances the flexural strength, but a decrease of the compressive strength is observed. A greater porosity of the concrete was also observed with the incorporation of flax fibers. An increase in porosity was also observed when increasing the paste content. (C) 2017 Elsevier Ltd. All rights reserved.
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Multi-physical properties of a structural concrete incorporating short flax fibers
Construction and Building Materials, 2017Co-Authors: Jonathan Page, Fouzia Khadraoui, Mohamed Boutouil, Moussa GominaAbstract:Abstract An experimental investigation was undertaken on the physical characterization of a flax fiber-reinforced concrete (FFRC) in both fresh and Hardened State. The objective of this study is to provide guidance for the mix-design of these FFRC. The study was conducted from two points of views: improving the workability of the concrete in a fresh State and improving the flexural strength in the Hardened State. Several parameters have been studied independently as fiber length, fiber content, or the paste content. The characterization of flax fibers highlighted a high water absorption capacity which must be taken into account for the concrete mix-design. In addition, the flax fibers significantly impact the compactness of granular skeleton. For the characterization of concrete, testing in the fresh State showed a significant decrease of the workability of concrete with the addition of flax fibers. However, the use of shorter fibers, allows to reduce this damaging influence on the fresh concrete workability. Moreover, increasing the paste content allows compensating this fluidity loss. In the Hardened State, the increase of the fiber content enhances the flexural strength, but a decrease of the compressive strength is observed. A greater porosity of the concrete was also observed with the incorporation of flax fibers. An increase in porosity was also observed when increasing the paste content.
Jonathan Page - One of the best experts on this subject based on the ideXlab platform.
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Influence of different surface treatments on the water absorption capacity of flax fibres: Rheology of fresh reinforced-mortars and mechanical properties in the Hardened State
Construction and Building Materials, 2019Co-Authors: Jonathan Page, Fouzia Khadraoui, Moussa Gomina, Mohamed BoutouilAbstract:Abstract An experimental investigation was undertaken on the influence of different surface treatments of flax fibres on mortar properties in both fresh and Hardened States. Three types of coating were explored for surface modification: atmospheric-pressure plasma, mineral coating made of a grout of cement and ground granulated blast-furnace slag, and polymer coating based on linseed oil. Water absorption tests were performed to evaluate the performance of the coatings. Water absorption kinetics and/or water retention capacity were drastically modified by the plasma treatment at atmospheric-pressure and by the linseed oil treatment. The workability of the pastes incorporating fibres coated with the cement grout or linseed oil was greatly improved compared to the raw fibres. The presence of fibres significantly increases the rate of entrapped air, which seems to depend on the nature of the coating. In the Hardened State, regardless of the nature of the fibre coating, the flexural strength increases beyond 90 days of curing. Up to 320 days of curing, the compressive strengths of the different composites are similar to that of the control mortar, except for the composite with linseed oil coated-fibres which proves to be the most porous. The presence of flax fibres also enhances the mortar toughness and prevent from desiccation cracking. Nevertheless, none of the treatments experimented in this work makes it possible to preserve the beneficial effects of fibres on the mechanical behaviour of composites in the long term.
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Multi-physical properties of a structural concrete incorporating short flax fibers
Construction and Building Materials, 2017Co-Authors: Jonathan Page, Fouzia Khadraoui, Mohamed Boutouil, Moussa GominaAbstract:An experimental investigation was undertaken on the physical characterization of a flax fiber-reinforced concrete (FFRC) in both fresh and Hardened State. The objective of this study is to provide guidance for the mix-design of these FFRC. The study was conducted from two points of views improving the workability of the concrete in a fresh State and improving the flexural strength in the Hardened State. Several parameters have been studied independently as fiber length, fiber content, or the paste content. The characterization of flax fibers highlighted a high water absorption capacity which must be taken into account for the concrete mix-design. In addition, the flax fibers significantly impact the compactness of granular skeleton. For the characterization of concrete, testing in the fresh State showed a significant decrease of the workability of concrete with the addition of flax fibers. However, the use of shorter fibers, allows to reduce this damaging influence on the fresh concrete workability. Moreover, increasing the paste content allows compensating this fluidity loss. In the Hardened State, the increase of the fiber content enhances the flexural strength, but a decrease of the compressive strength is observed. A greater porosity of the concrete was also observed with the incorporation of flax fibers. An increase in porosity was also observed when increasing the paste content. (C) 2017 Elsevier Ltd. All rights reserved.
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Multi-physical properties of a structural concrete incorporating short flax fibers
Construction and Building Materials, 2017Co-Authors: Jonathan Page, Fouzia Khadraoui, Mohamed Boutouil, Moussa GominaAbstract:Abstract An experimental investigation was undertaken on the physical characterization of a flax fiber-reinforced concrete (FFRC) in both fresh and Hardened State. The objective of this study is to provide guidance for the mix-design of these FFRC. The study was conducted from two points of views: improving the workability of the concrete in a fresh State and improving the flexural strength in the Hardened State. Several parameters have been studied independently as fiber length, fiber content, or the paste content. The characterization of flax fibers highlighted a high water absorption capacity which must be taken into account for the concrete mix-design. In addition, the flax fibers significantly impact the compactness of granular skeleton. For the characterization of concrete, testing in the fresh State showed a significant decrease of the workability of concrete with the addition of flax fibers. However, the use of shorter fibers, allows to reduce this damaging influence on the fresh concrete workability. Moreover, increasing the paste content allows compensating this fluidity loss. In the Hardened State, the increase of the fiber content enhances the flexural strength, but a decrease of the compressive strength is observed. A greater porosity of the concrete was also observed with the incorporation of flax fibers. An increase in porosity was also observed when increasing the paste content.
Moussa Gomina - One of the best experts on this subject based on the ideXlab platform.
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Influence of different surface treatments on the water absorption capacity of flax fibres: Rheology of fresh reinforced-mortars and mechanical properties in the Hardened State
Construction and Building Materials, 2019Co-Authors: Jonathan Page, Fouzia Khadraoui, Moussa Gomina, Mohamed BoutouilAbstract:Abstract An experimental investigation was undertaken on the influence of different surface treatments of flax fibres on mortar properties in both fresh and Hardened States. Three types of coating were explored for surface modification: atmospheric-pressure plasma, mineral coating made of a grout of cement and ground granulated blast-furnace slag, and polymer coating based on linseed oil. Water absorption tests were performed to evaluate the performance of the coatings. Water absorption kinetics and/or water retention capacity were drastically modified by the plasma treatment at atmospheric-pressure and by the linseed oil treatment. The workability of the pastes incorporating fibres coated with the cement grout or linseed oil was greatly improved compared to the raw fibres. The presence of fibres significantly increases the rate of entrapped air, which seems to depend on the nature of the coating. In the Hardened State, regardless of the nature of the fibre coating, the flexural strength increases beyond 90 days of curing. Up to 320 days of curing, the compressive strengths of the different composites are similar to that of the control mortar, except for the composite with linseed oil coated-fibres which proves to be the most porous. The presence of flax fibres also enhances the mortar toughness and prevent from desiccation cracking. Nevertheless, none of the treatments experimented in this work makes it possible to preserve the beneficial effects of fibres on the mechanical behaviour of composites in the long term.
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Multi-physical properties of a structural concrete incorporating short flax fibers
Construction and Building Materials, 2017Co-Authors: Jonathan Page, Fouzia Khadraoui, Mohamed Boutouil, Moussa GominaAbstract:An experimental investigation was undertaken on the physical characterization of a flax fiber-reinforced concrete (FFRC) in both fresh and Hardened State. The objective of this study is to provide guidance for the mix-design of these FFRC. The study was conducted from two points of views improving the workability of the concrete in a fresh State and improving the flexural strength in the Hardened State. Several parameters have been studied independently as fiber length, fiber content, or the paste content. The characterization of flax fibers highlighted a high water absorption capacity which must be taken into account for the concrete mix-design. In addition, the flax fibers significantly impact the compactness of granular skeleton. For the characterization of concrete, testing in the fresh State showed a significant decrease of the workability of concrete with the addition of flax fibers. However, the use of shorter fibers, allows to reduce this damaging influence on the fresh concrete workability. Moreover, increasing the paste content allows compensating this fluidity loss. In the Hardened State, the increase of the fiber content enhances the flexural strength, but a decrease of the compressive strength is observed. A greater porosity of the concrete was also observed with the incorporation of flax fibers. An increase in porosity was also observed when increasing the paste content. (C) 2017 Elsevier Ltd. All rights reserved.
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Multi-physical properties of a structural concrete incorporating short flax fibers
Construction and Building Materials, 2017Co-Authors: Jonathan Page, Fouzia Khadraoui, Mohamed Boutouil, Moussa GominaAbstract:Abstract An experimental investigation was undertaken on the physical characterization of a flax fiber-reinforced concrete (FFRC) in both fresh and Hardened State. The objective of this study is to provide guidance for the mix-design of these FFRC. The study was conducted from two points of views: improving the workability of the concrete in a fresh State and improving the flexural strength in the Hardened State. Several parameters have been studied independently as fiber length, fiber content, or the paste content. The characterization of flax fibers highlighted a high water absorption capacity which must be taken into account for the concrete mix-design. In addition, the flax fibers significantly impact the compactness of granular skeleton. For the characterization of concrete, testing in the fresh State showed a significant decrease of the workability of concrete with the addition of flax fibers. However, the use of shorter fibers, allows to reduce this damaging influence on the fresh concrete workability. Moreover, increasing the paste content allows compensating this fluidity loss. In the Hardened State, the increase of the fiber content enhances the flexural strength, but a decrease of the compressive strength is observed. A greater porosity of the concrete was also observed with the incorporation of flax fibers. An increase in porosity was also observed when increasing the paste content.
J. L. Barroso De Aguiar - One of the best experts on this subject based on the ideXlab platform.
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Incorporation of titanium dioxide nanoparticles in mortars — Influence of microstructure in the Hardened State properties and photocatalytic activity
Cement and Concrete Research, 2013Co-Authors: S. S. Lucas, Victor M. Ferreira, J. L. Barroso De AguiarAbstract:The environmental pollution in urban areas is one of the causes for poor indoor air quality in buildings, particularly in suburban areas. The development of photocatalytic construction materials can contribute to clean the air and improve sustainability levels. Previous studies have focused mainly in cement and concrete materials, disregarding the potential application in historic buildings. In this work, a photocatalytic additive (titanium dioxide) was added to mortars prepared with aerial lime, cement and gypsum binders. The main goal was to study the way that microstructural changes affect the photocatalytic efficiency. The photocatalytic activity was determined using a reactor developed to assess the degradation rate with a common urban pollutant, NOx. The laboratory results show that all the compositions tested exhibited high photocatalytic efficiency. It was demonstrated that photocatalytic mortars can be applied in new and old buildings, because the nanoadditives do not compromise the mortar Hardened State properties.
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Latent heat storage in PCM containing mortars - study of microstructural modifications
Energy and Buildings, 2013Co-Authors: S. S. Lucas, Victor M. Ferreira, J. L. Barroso De AguiarAbstract:The incorporation of phase change materials (PCM) into traditional mortars give to these products the ability to store and release heat. In this way it is possible to reduce the energy consumption and improve the thermal comfort in buildings. The introduction of micro and nanomaterials in the mortars matrix can cause microstructural changes that need to be addressed in order to optimize the PCM addition. The relationship between the Hardened State performance of different PCM-mortars, its internal microstructure and pore distribution as been observed for different binders such as lime, cement and gypsum. Their Hardened State properties, microstructural modifications and heat storage capabilities were evaluated. The ability to store and release heat depends strongly on the size and distribution of internal pores and not only on the PCM content. Using a thermal efficiency test, an important correlation between thermal performance and the mortars microstructure was established, for mortars with 0–30% of PCM added.
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Energy and Buildings
2013Co-Authors: S. S. Lucas, Victor M. Ferreira, J. L. Barroso De AguiarAbstract:a b s t r a c t The incorporation of phase change materials (PCM) into traditional mortars give to these products the ability to store and release heat. In this way it is possible to reduce the energy consumption and improve the thermal comfort in buildings. The introduction of micro and nanomaterials in the mortars matrix can cause microstructural changes that need to be addressed in order to optimize the PCM addition. The relationship between the Hardened State performance of different PCM-mortars, its internal microstruc- ture and pore distribution as been observed for different binders such as lime, cement and gypsum. Their Hardened State properties, microstructural modifications and heat storage capabilities were evaluated. The ability to store and release heat depends strongly on the size and distribution of internal pores and not only on the PCM content. Using a thermal efficiency test, an important correlation between thermal performance and the mortars microstructure was established, for mortars with 0-30% of PCM added. © 2013 Elsevier B.V. All rights reserved.
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Fresh State characterization of lime mortars with PCM additions
Applied Rheology, 2010Co-Authors: S. S. Lucas, L Senff, Victor M. Ferreira, J. L. Barroso De Aguiar, João A. LabrinchaAbstract:The application of sustainability principles in construction encourages the development of new products, with new functionalities and applications, able to improve buildings environmental performance. The use of latent heat storage materials in lime mortars aims to reduce the energy consumption of buildings. This work intends to evaluate the impact of phase change materials (PCM) incorporation in rheological and Hardened State properties of aerial lime mortars. A fresh State characterization was conducted through the rheological study complemented with flow table tests of different mortar formulations. To complete the mortar characterization some Hardened State properties (porosity, mechanical strength and microstructure) after 28 days, were also evaluated. It was concluded that, the PCM microcapsules incorporation does not compromise aerial lime mortars overall performance and may help to improve some characteristics like workability and mechanical strength. Therefore, it is possible to reduce the energy demand in old buildings, improving their performance and sustainability.
