Effet du nanorenforcement sur les propriétés physico-mécaniques et la durabilité des PRF utilisés en génie civil

Depuis des années, les polymères renforcés de fibres (PRF) sont de plus en plus utilisés, notamment dans le domaine du génie civil. Ces matériaux composites sont rigides, tenaces, légers et ils sont inertes face à la corrosion électrochimique, ce qui en fait d’excellents candidats pour de nombreuses applications, par exemple comme barres d’armature dans le béton ou en réhabilitation externe des structures. Récemment, la communauté scientifique s’est tournée vers l’utilisation des nanocomposites polymère (PNC), matériaux biphasés constitués d’une matrice polymère mélangée à des nanoparticules. La très grande surface spécifique de ces dernières augmente significativement les propriétés mécaniques, thermiques ou barrières des polymères. Ces PNC sont de bons candidats pour la réhabilitation et le renforcement des structures en béton. Cependant, les matériaux à matrice polymère soulèvent diverses questions, comme leur dégradation face à l’environnement d’application, humide et parfois alcalin, ou leur mauvaise interface fibre/matrice causée par les natures différentes des fibres hydrophiles et des matrices polymères hydrophobes. Pour répondre à ces problématiques, cette étude porte sur le nanorenforcement des PRF à matrice polymère thermodurcissable utilisés en génie civil. Des nanoparticules, dispersées dans les matrices polymères sous forme de feuillets, induisent un phénomène de tortuosité limitant la diffusion au sein du matériau, augmentant ainsi la durabilité. Ces feuillets peuvent être des argiles, comme les silicates, ou des graphites exfoliés, comme le graphène. Pour améliorer l’interface fibre/résine des PRF, des traitements de surface sur des fibres minérales et naturelles sont effectués pour améliorer leur affinité avec des matrices thermodurcissables. Les objectifs principaux du nanorenforcement sont de : (1) augmenter les propriétés barrières des vinylesters pour augmenter leur durabilité et (2) améliorer l’interface dans les PRF à matrice thermodurcissable. Les résultats montrent que l’intercalation de nanoargiles dans les vinylesters augmente sensiblement la durabilité du polymère, en limitant la diffusion d’humidité au sein du matériau, tout en stoppant l’hydrolyse de la matrice. L’addition de faibles fractions (0.5 % en poids) de graphène oxydé augmente ainsi de plus de 15% les propriétés en flexion du polymère, tout en diminuant l’absorption à saturation (- 8%). À l’interface fibre/matrice, le nanorenforcement réalisé avec de la fumée de silice ou des nanocristaux d’amidon augmente non seulement les propriétés en traction des fibres de basalte et de bambou (jusqu’à 20%), mais aussi leurs interfaces avec les matrices thermodurcissables (vinylester et bio-époxy), avec une augmentation de plus de 25% des propriétés mécaniques des PRF réalisés avec ces fibres modifiées

Enhancing mechanical performance of green fiber cement composites:Role of eco-friendly alkyl ketene dimer on surfaces of hemp fibers

Fiber composites reinforced natural fibers have attracted more attention in sustainable building materials due to the high Young's modulus, availability, and biodegradability. However, poor interfacial bonding of the fiber-reinforced cement composites attributed to the intrinsically swelling-shrinkage behavior of the hydrophilic natural fibers, seriously limits the strength development of the composite. Here, an eco-friendly and low-cost surface treatment agent, alkyl ketene dimer (AKD), is innovatively introduced for reinforcing the combined effect of hemp fiber (HF)/cement matrix. The experimental approach includes the chemical modification of hemp fibers, followed by the direct preparation of fiber cement composites. Fourier transformation infrared spectroscopy (FTIR) and water absorption test analyses confirmed that the modified HF surface was successfully grafted with AKD, leading to superior hydrophobic characterization and reduced swelling-shrinking behavior. Adding the modified HF to the cement composites effectively enhanced their mechanical properties and toughness capacity by strengthening the interfacial bond of modified HF/Mortar. The modified fiber-reinforced mortar has the highest increment (28 % in compressive strength and 24 % in flexural strength, respectively) from 7 d to 28 d among all investigated mortars. Furthermore, the micro-observation of fractured mortar composites supports the strengthened interface of the modified fibers/cement matrix. The study provides a feasible and practical approach to improving the comprehensive strength properties of hemp fiber-reinforced cement composites. It benefits the practical industrial-scale application of biomaterials in low-cost housing, thus enhancing sustainability

Improving the interface compatibility and mechanical performances of the cementitious composites by low-cost alkyl ketene dimer modified fibers

Natural fibers-reinforced cement composites have recently attracted more interest due to the trend in the development of sustainable construction materials. However, the poor fiber–matrix interface compatibility, which is caused by the swelling-shrinking behavior of hydrophilic natural fiber, negatively affects the mechanical properties of the composites thereby hindering their practical application. In order to promote interfacial compatibility, a new fiber surface treatment is needed. A low-cost alkyl ketene dimer (AKD) is adopted in this work, aiming at replacing the relatively expensive silane agents. This study focuses on fiber surface treatment and the resulting effects on the interface compatibility and mechanical performances of the composites. The effect of the fiber modification was characterized by FTIR and water absorption test; The interfacial compatibility of the composites was evaluated by the compatibility index calculation and SEM observation; A series of strength properties of the composites were carried out considering the influence of interface compatibility on mechanical performance. Results show a clear improvement in both interface compatibility and mechanical properties of the composites when AKD-modified fibers are used as reinforcement. The compressive and flexural strength are effectively increased up to 53 MPa and 8 MPa, respectively. Moreover, the approach of the low-cost AKD modification could further be applied to any natural fibers in cementitious composites, allowing cost-effectiveness in practical applications

Emission rates of bio-based building materials, a method description for qualifying and quantifying VOC emissions

Biobased insulation materials offer opportunities to use vapor-open building constructions. Such constructions allow direct interaction between the biobased material and the indoor environment. This interaction raises questions about indoor air quality concerning volatile organic compounds (VOCs). This study presents results for the VOC emissions from biobased materials. It consists of two parts: 1) qualification of VOC emissions (compounds) from several biobased and non-biobased building materials, and 2) quantification of VOC emissions (emission rate) from expanded cork (biobased), particle board (semi-biobased), and EPS insulation. By quantifying the emission rate, the exposure to the released VOC emissions at room temperature in a standardized room can be compared to health limit requirements. Gas chromatography and mass spectroscopy (GC–MS) is used to derive the individual VOC emissions and the Total Volatile Organic Compounds (TVOC) from these materials. For qualification, two different sampling techniques are used in which temperature is introduced as a variable to investigate its effect on the type of compounds emitted. For quantification, the toluene equivalent approach is compared to the group equivalent approach. From the analyses it is concluded that temperature has an effect on the type of VOC compounds emitted from (biobased) materials. Results from the quantification indicate that expanded cork and particle board emit no harmful substances at a level that can affect human health. For EPS insulation, elevated levels of benzene were found to exceed healthy limits. The toluene equivalent approach for quantifying the emission, generally, underestimates the rate as compared to the more accurate group equivalent approach

Utilization of air granulated basic oxygen furnace slag as a binder in belite calcium sulfoaluminate cement: A sustainable alternative

Basic oxygen furnace (BOF) slag negatively impacts ordinary Portland cement performance when replacement levels exceed 5%. This necessitates the exploration of alternative applications for the slag. Simultaneously, a high-volume slag utilization is desired to benefit slag recycling as supplementary cementitious materials. Therefore, this study aims to optimize the air granulated BOF slag substitution potential in belite calcium sulfoaluminate cement by investigating the hydration products in standard mortar. The reactivity of the novel binder is correlated with workability, and mechanical performance by thermal, mineralogical, and microstructure analysis. Consequently, the 10–30% replacement delays the final setting time by inhibiting the ettringite formation leading to a decrease in mechanical performance till 28 days. At later ages (28–180 days), the 30–50% substitution exhibited the synergy in mechanical performance, which is attributed to the hydrogarnet, calcium silicate hydrate, and strätlingite formation. Moreover, all the mortar samples exhibited heavy metals’ leaching and drying shrinkage below the permissible limit.</p

Effet du nanorenforcement sur les propriétés physico-mécaniques et la durabilité des PRF utilisés en génie civil

Depuis des années, les polymères renforcés de fibres (PRF) sont de plus en plus utilisés, notamment dans le domaine du génie civil. Ces matériaux composites sont rigides, tenaces, légers et ils sont inertes face à la corrosion électrochimique, ce qui en fait d’excellents candidats pour de nombreuses applications, par exemple comme barres d’armature dans le béton ou en réhabilitation externe des structures. Récemment, la communauté scientifique s’est tournée vers l’utilisation des nanocomposites polymère (PNC), matériaux biphasés constitués d’une matrice polymère mélangée à des nanoparticules. La très grande surface spécifique de ces dernières augmente significativement les propriétés mécaniques, thermiques ou barrières des polymères. Ces PNC sont de bons candidats pour la réhabilitation et le renforcement des structures en béton. Cependant, les matériaux à matrice polymère soulèvent diverses questions, comme leur dégradation face à l’environnement d’application, humide et parfois alcalin, ou leur mauvaise interface fibre/matrice causée par les natures différentes des fibres hydrophiles et des matrices polymères hydrophobes. Pour répondre à ces problématiques, cette étude porte sur le nanorenforcement des PRF à matrice polymère thermodurcissable utilisés en génie civil. Des nanoparticules, dispersées dans les matrices polymères sous forme de feuillets, induisent un phénomène de tortuosité limitant la diffusion au sein du matériau, augmentant ainsi la durabilité. Ces feuillets peuvent être des argiles, comme les silicates, ou des graphites exfoliés, comme le graphène. Pour améliorer l’interface fibre/résine des PRF, des traitements de surface sur des fibres minérales et naturelles sont effectués pour améliorer leur affinité avec des matrices thermodurcissables. Les objectifs principaux du nanorenforcement sont de : (1) augmenter les propriétés barrières des vinylesters pour augmenter leur durabilité et (2) améliorer l’interface dans les PRF à matrice thermodurcissable. Les résultats montrent que l’intercalation de nanoargiles dans les vinylesters augmente sensiblement la durabilité du polymère, en limitant la diffusion d’humidité au sein du matériau, tout en stoppant l’hydrolyse de la matrice. L’addition de faibles fractions (0.5 % en poids) de graphène oxydé augmente ainsi de plus de 15% les propriétés en flexion du polymère, tout en diminuant l’absorption à saturation (- 8%). À l’interface fibre/matrice, le nanorenforcement réalisé avec de la fumée de silice ou des nanocristaux d’amidon augmente non seulement les propriétés en traction des fibres de basalte et de bambou (jusqu’à 20%), mais aussi leurs interfaces avec les matrices thermodurcissables (vinylester et bio-époxy), avec une augmentation de plus de 25% des propriétés mécaniques des PRF réalisés avec ces fibres modifiées

Enhancing mechanical performance of green fiber cement composites: Role of eco-friendly alkyl ketene dimer on surfaces of hemp fibers

Fiber composites reinforced natural fibers have attracted more attention in sustainable building materials due to the high Young's modulus, availability, and biodegradability. However, poor interfacial bonding of the fiber-reinforced cement composites attributed to the intrinsically swelling-shrinkage behavior of the hydrophilic natural fibers, seriously limits the strength development of the composite. Here, an eco-friendly and low-cost surface treatment agent, alkyl ketene dimer (AKD), is innovatively introduced for reinforcing the combined effect of hemp fiber (HF)/cement matrix. The experimental approach includes the chemical modification of hemp fibers, followed by the direct preparation of fiber cement composites. Fourier transformation infrared spectroscopy (FTIR) and water absorption test analyses confirmed that the modified HF surface was successfully grafted with AKD, leading to superior hydrophobic characterization and reduced swelling-shrinking behavior. Adding the modified HF to the cement composites effectively enhanced their mechanical properties and toughness capacity by strengthening the interfacial bond of modified HF/Mortar. The modified fiber-reinforced mortar has the highest increment (28 % in compressive strength and 24 % in flexural strength, respectively) from 7 d to 28 d among all investigated mortars. Furthermore, the micro-observation of fractured mortar composites supports the strengthened interface of the modified fibers/cement matrix. The study provides a feasible and practical approach to improving the comprehensive strength properties of hemp fiber-reinforced cement composites. It benefits the practical industrial-scale application of biomaterials in low-cost housing, thus enhancing sustainability

Effect of modified graphene oxide on the mechanical, thermal, and barrier properties of vinylester

Graphene, which is a one atom thick layer of graphite, has been considerably studied in the past decade due to its extraordinary physical properties. The development of new routes of synthesis facilitates the use of graphene in polymer nanocomposite. The addition of very small amounts (<1%) of graphene in a polymer matrix does not only increase its thermal and mechanical properties, but it would also enhance permeability, by limiting the diffusion of water through the material. Graphene-polymer nanocomposite would be an interesting alternative to conventional polymer nanocomposite such as nanoclay-polymer nanocomposite. In this study, graphene oxide is synthesized from graphite flakes, following the Tour method, and modified with silane to improve its compatibility with the polymer. Polymer nanocomposite made from vinylester resin and 0.5 wt% graphene oxide is prepared as well as other types of typically used polymer nanocomposite such as graphite flake, silica fume or nanoclay based composite. Samples are soaked in a water bath to study the water absorption of these nanocomposites. Mechanical property measurements and thermal analyses are performed to evaluate the benefit of using graphene oxide. Results show a significant enhancement of the mechanical and thermal properties with a graphene oxide content ten times lower than the one needed with conventional nanoparticles. Moreover, unlike nanoclay-based polymer nanocomposite, graphene oxide does not increase water absorption at saturation

The recycling potential of wood waste into wood-wool/cement composite

Nowadays, the recycling potential of wood waste is still limited and in a resource cascading approach,recycling wood waste in cement composite materials, such as wood wool cement board (WWCB) appears as a promising solution. The quality of the wood waste is the main factor leading to the instability of the final product which can affect the mechanical properties or the wood cement compatibility. However, the possibility to recycle wood waste as a spruce replacement for WWCB manufacture needs more investigation in order to assess the impact of wood waste on the mechanical performances of the final product,but also to characterize the behavior of hazardous substances embodied in a cement matrix. This paper addresses the characterization of two types of wood waste, from pallets and demolition waste and their influence on the manufacturing process, mechanical properties and chemical compatibility when used in WWCB. A comprehensive approach is provided to define the influence of wood waste on the hydration reaction of the cement and the chemical and physical properties of the composite are assessed by isothermal calorimetry, leaching measurement and microscopy. Finally, the mechanical properties of WWCB are tested for different wood waste content in order to define the best wood/wood waste ratio and thereby confirming the possibility to reuse the wood waste in fiber/cement composite for building application

Investigation of sisal fiber incorporation on engineering properties and sustainability of lightweight aggregates produced from municipal solid waste incinerated bottom ash

The large-scale disposal of bottom ash resulting from municipal solid waste incineration poses a significant challenge in terms of effective management. While Lightweight aggregates made of municipal solid waste incinerated bottom ash, referred to as MSWI BA, show promise, their practical application is hindered by low structural strength and the presence of certain contaminants. To address this, a novel and green solution is proposed in this study, which involves utilizing sisal fibers (SF) to enhance the solidification of the synthesized aggregates. In this study, the synthesized lightweight aggregates (SLWAs) consisting of cement, different replacement levels of ground MSWI BA (60%, 70%, and 80%), and/or the cut SF were manufactured by a disc pelletizer. The influence of incorporating SF on the SLWAs was investigated across various aspects, encompassing the physical characteristics, strength performance, microscopic properties, and sustainability. The results showed that when SF was incorporated, the production efficiency of coarse SLWAs was considerably improved, especially up to a 66.5% increase with under the 70% replacement level of MSWI BA. Moreover, the surface roughness and strength were improved due to the SF addition. In the system of the CEM-MSWI BA matrix, the fiber incorporation not only accelerates the cement hydration reaction but also fills the pore generated from the swelling of metallic aluminum in MSWI BA, achieving the strength enhancement of SLWAs. More importantly, some contaminant ions including chloride, chromium, and copper from MSWI BA, could be effectively absorbed and solidified by the SF. Furthermore, the utilization of SF in SLWAs brings about great sustainability concerning greenhouse gas emissions and production costs. Consequently, incorporating SF proves to be an effective and green solution, thus promoting the practical implementation of the SLWAs