Article

Study of a hempcrete wall exposed to outdoor climate: Effects of the coating

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Abstract

Hemp concrete is becoming a popular building construction material, as it has a low environmental impact and helps reducing the heat conductivity of walls. The generally used binder is lime, but in this study a prompt natural cement binder was used. The objective of this study was to analyse the behaviour of a hempcrete wall in realistic conditions. 2 test walls made of prefabricated hemp concrete blocks were built. Those walls were exposed to the outdoor climate on the one side, and to a controlled indoor climate on the other side. 2 different exterior coatings were applied. The experiment lasted one year. In addition, numerical simulations were carried out. The model was used to determine the material properties and to help understand the behaviour measured. The results show that an important humidification of the wall can occur if the coating is not well chosen. The exterior coating must be very permeable to water vapour, but it seems to be important to prevent the absorption of rain as well, otherwise, the humidity inside the wall can lead to degradations such as mould growth or increased thermal conductivity. Both numerical simulation and measurements show that applying a vapour permeable coating on the blocks does not slow down the drying process, the hempcrete itself being the limiting factor.

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... Several researchers have published varying results for the density of hempcrete, ranging from 300 to 900 kg/m 3 (Arnaud and Gourlay, 2011;Cerezo, 2005;Cigasova et al., 2014;Elfordy et al., 2008;Evrard, 2003;Kioy, 2005;Nguyen et al., 2009;Piot et al., 2017). However, the material has never lost its lightweight status always remaining well below the 1000 kg/m 3 density mark. ...
... However, they had found that hemp concrete is fairly resistant to sodium chloride salt exposure and biological deterioration due to microbial attack (Walker et al., 2014). Contrarily, Piot et al., 2017 had reported the growth of mould just beneath the surface of the coating they had applied to their test specimens. They had tested their hemp concrete specimens for an entire year (Piot et al., 2017). ...
... Contrarily, Piot et al., 2017 had reported the growth of mould just beneath the surface of the coating they had applied to their test specimens. They had tested their hemp concrete specimens for an entire year (Piot et al., 2017). emissions made from all other processes related to constructing the structures. ...
Conference Paper
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With the alarming global increase in carbon emissions and its implications, the need for carbon neutral or carbon negative technologies is of utmost importance and urgency. Cellulose aggregate concrete (CAC) or bio-aggregate concrete has not only the multi-benefits of low density, better thermal insulation and low embodied energy, it can also make use of industrial wastes such as fly ash, slag, etc. One such CAC is called hemp concrete, which is a composite made of hemp shiv and lime based binder. Hemp is one of the world's earliest cultivated crops and has a variety of applications including construction. This paper discusses various properties and applications of hemp and hemp concrete such as mechanical performance and durability, with a focus on its carbon sequestration ability and carbon negativity, and the current research interest as well as its possible contribution towards solution of climate change problems.
... Binder type can affect capillary action within the material and increasing the hydraulicity of the binder as well as using water retainer can reduce capillary absorption [169,186]. Hempcrete isn't degradation proof against long-term exposure to rain or extreme humidity [187] and noticeable deformation may occur above 60% moisture content [172], although in the short term exposure, moisture might not propagate deeply into the hempcrete [195]. In a normal situation, shiv shows slow mineralization under the action of lime which makes the composite inert and reduces the risk of rot and mold growth [177]. ...
... In a normal situation, shiv shows slow mineralization under the action of lime which makes the composite inert and reduces the risk of rot and mold growth [177]. To prevent the absorption of rain and excessive humidification inside the wall, some researchers suggested using coating or breathable finishing [196] to avoid the possible problem of mold growth over the long run [195]. ...
... In the case of building materials, this phenomenon is critical since the energy efficiency of a building is greatly affected by the hygrothermal behavior of constituent materials [197]. Air has a low thermal conductivity; therefore, bio-based materials like hempcrete having a highly porous structure result in a lightweight and low thermally conductive material offering better thermal comfort inside the building [186,187,195]. The heat transmission of hempcrete ranges from 0.06 to 0.19 W.m -1 .K -1 for dry densities between 200 and 840 kg.m -3 [174]. ...
Article
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Global warming as a result of climate change has become a major concern for people all over the world. It has recently drawn the attention of the entire conscious community, with the fear that if not addressed properly, it will result in the extinction of numerous species around the world. At the same time, it will pose a threat to human health, food security, living environment and standard of living. Thereby, possible solutions are being explored accordingly, regulations have been imposed in places binding green production practices, limiting the emission of CO2 and emphasis is given on renewable resources along with the search for alternatives to carbon-positive materials. Cannabis sativa L. (hemp) has received a lot of attention because of its multipurpose usability, short production cycle, low capital demand in cultivation, possibility of carbon-negative transformation and easy carbon sequestering material. This paper reviews hemp as a very promising renewable resource including its potential uses in paper, textiles, composites, biofuel, and food industry.
... The higher the moisture buffer value, the greater is the ability of the material to regulate the ambient relative humidity. Piot et al. (2017) had studied the hygrothermal behavior of a wall made from a proprietary mix of hempcrete having a dry density of 350 kg/m 3 in outdoor climatic conditions. Their test setup consisted of two test cells, which were coated with two types of exterior coatings e industrial pre-mixed additives, lime, and cement based; and hand mixed lime and cement based. ...
... The hygric inertia of hempcrete results in the presence of a "perennial wetness" within the wall, which is detrimental to the building performance on two fronts e thermal conductivity and durability. Piot et al. (2017) had reported that choosing an exterior coating or plaster that absorbs water affects the thermal conductivity of the hempcrete wall by making it more conductive. Another risk associated with choosing a water-absorbing exterior coating is the growth of mold just underneath the coating. ...
... Walker et al. (2014) had suggested the use of additives to improve the strength and durability of lime-pozzolan binder based hemp concretes. Piot et al. (2017) had discovered mold growth just underneath a hand-mixed exterior coating on their hempcrete walls, which were studied for an entire year exposed to outdoor conditions. Their test procedure is outlined in section 4.7. ...
Article
The growing concerns surrounding the rising carbon emissions have impelled the leaders around the world to make efforts to prevent catastrophic manifestations of climate change and global warming. This has led to the resurrection of vegetal concrete building materials using biomass, which have the added benefits of carbon sequestration apart from low embodied energy and renewability. Vegetal concretes are made up of an organic or inorganic binder, and biomass originating from agro-forestry industries such as rice husk, straw bale, hemp, kenaf, cork, and so on. Hemp concrete, a variety of vegetal concrete has been widely researched and is arguably one of the most researched building materials in current times. This paper presents a review of the state-of-the-art of hemp concrete research, with a view to identifying research gaps that shall guide future research for its implementation in the fast-growing green buildings industry. The reviewed aspects of hemp concrete include properties of hemp relevant to construction, binder characteristics, mechanical properties, durability, hygric and thermal properties, environmental credentials, manufacturing processes, and current applications. Several research gaps with regards to the hydraulicity of the binder, strength and durability, and fire resistance of hemp concrete were identified. It was also established that hemp concrete has very low embodied carbon and embodied energy, making it ideal for green building applications. The paper ends with a discussion outlining the need and direction for future research on improving the manufacturing processes and mechanical performance of hemp concrete for wider adoption by the construction industry.
... The ability of a substance to modify ambient relative humidity is proportional to its moisture buffer value. Under outdoor climatic conditions, Piot et al. (2017) [86] evaluated the hygrothermal behaviour of a wall composed of a proprietary hempcrete mix with a dry density of 350 kg/m 3 . A computer model was used to calculate heat conduction and storage, as well as vapour diffusion, liquid capillary movement, and moisture storage. ...
... The ability of a substance to modify ambient relative humidity is proportional to its moisture buffer value. Under outdoor climatic conditions, Piot et al. (2017) [86] evaluated the hygrothermal behaviour of a wall composed of a proprietary hempcrete mix with a dry density of 350 kg/m 3 . A computer model was used to calculate heat conduction and storage, as well as vapour diffusion, liquid capillary movement, and moisture storage. ...
Article
A simple mixture of hemp hurd, water, and lime is used to make hemp concrete. It is indeed one of the few materials that can continue to absorb carbon after being employed in construction, storing more carbon in the atmosphere over the building's lifetime than was emitted during construction. Furthermore, hemp can be harvested in as little as 60 days. Hemp concrete is a “carbon-negative” or “better-than-zero-carbon” substance because the hemp plant absorbs more carbon from the atmosphere than it emits during its production and application on site. It is a bio-composite material that can be utilised as an alternative to concrete and standard insulation in building. Hemp concrete is also recyclable at the end of the building's lifespan. This study summarises the fast-developing body of knowledge about hemp concrete, which was recently developed.
... Dans le cas d'enduits isolants, le matériau devra au minimum supporter son poids propre, la norme allemande DIN 4108-10 concernant les matériaux d'isolation thermiques manufacturés fixant la contrainte à atteindre en compression simple à 0,02MPa.La quantité d'eau présente à l'instant t dans un matériau d'isolation impacte sensiblement ses performances thermiques, les concepteurs peuvent chercher à profiter de cette caractéristique et favoriser l'absorption de vapeur d'eau avec pour objectif de lisser les pics d'humidité à l'intérieur des pièces d'un habitat pour en augmenter le confort et profiter des effets thermodynamique liés à la condensation et l'évaporation de vapeur d'eau dans les matériaux engendrant des phénomènes passifs de climatisation. La connaissance des propriétés hydriques de ces matériaux est par conséquent nécessaire pour l'interprétation de ses performances.La connaissance des phénomènes de capillarité propres aux matériaux d'isolation à base de végétaux est également cruciale car outre les performances thermiques fortement dégradées d'un matériau poreux imbibé d'eau, lorsque le liant utilisé est à base de terre-crue, la dégradation des propriétés mécaniques est un risque élevé menaçant l'intégrité du matériau et enfin, le risque d'un développement de moisissures comme cela a été constaté sur des bétons de chanvres exposés aux intempéries(Jay et al. 2017) avec des conséquences néfastes pour l'aspect sanitaire de la qualité de l'air intérieur.Optimiser les matériaux à base de terre-crue pour améliorer leurs performances mécaniques et diminuer leur sensibilité à l'immersion est devenu un axe de recherche pour l'amélioration des techniques de construction à base de terre crue. L'emploi d'additifs est une piste d'optimisation des mélanges terre-végétaux qui a été investiguée également ici de manière exploratoire et qui demanderait une étude plus approfondie dans un avenir immédiat ; de même l'empreinte environnementale engendrée par la stabilisation est questionnée. ...
... Ces simulations permettent également de mettre en avant que la durée de séchage de l'isolant biocomposite recouvert d'un enduit de finition à base d'argile est deux fois et demie plus importante que celle sans enduit. Toutefois, il a été constaté par Jay et al.(Jay et al. 2017) que la mise en place ou non d'un enduit de finition sur des blocs de chaux-chanvre non secs a un impact moindre sur la durée de séchage. La diminution de la période de séchage étant un facteur essentiel pour éviter l'apparition de moisissures dans l'isolant bio composite, une attention particulière doit être apportée sur le type d'enduit de finition à utiliser (ou son absence) au moment de la mise en oeuvre. ...
Thesis
Full-text available
The building sector (both for the construction and operation) is a major source of CO2 emissions worldwide, due to the energy consumption (heat, air ventilation and cooling) and materials production involved. Furthermore, the depletion of natural resources is becoming a critical issue; the use of renewable and recyclable resources, with low embodied energy is therefore relevant. In that respect, the use of agricultural by-products as lightweight aggregates for thermal insulation purposes is particularly judicious. They have low embodied energy and can be considered as waste with a positive carbon balance as they store CO2. Replacing Portland cement by local crude earth improves the material’s carbon footprint. The work presented here that claims the use of those ecologically friendly materials is carried out in the frame work of BIOCOMP project which aims to develop locally produced biocomposites to be used as houses interior insulating materials. This, to offer refurbishment solutions for vernacular buildings in Touraine, Center of France. In this study, samples have been prepared using 4 different vegetal aggregates (rape straw, sunflower bark, sunflower pith and a mix of sunflower pith and bark) and a characterized crude earth as binder for a same binder/aggregates ratio. The purpose of this study was to compare hygrothermal acoustical and mechanical properties of different materials based on vegetal aggregates and clay in order to characterize the performances of different biocomposites with a view to valorizing agricultural waste. We first analyzed the raw materials in order to get the density, thermal and hydric properties of the vegetal aggregates in one hand and the mineralogy and gravimetric data of the selected crude earth in the other hand. Thermal behavior of earth:vegetal aggregates mixes have been investigated at different humidity rates and different density ranges. Additionally, hydric properties have been measured to produce sorption and desorption curves and moisture buffer values (MBV) in one hand and capillarity of both aggregates and biocomposites on the other hand. Studying those hydric properties is relevant as a suitable insulating material for the refurbishment of the locally porous limestone made houses should offer good water vapor regulation. For the first time, we investigate here the thermal properties of mixes of crude earth with rape-straw and sunflower stem (bark and pith). According to the french NF P 75-101 standard, in order to be considered as building thermal insulator, a material should have a thermal conductivity below 0.065W.m-1.K-1. Lime-vegetal or clay-vegetal plasters can hardly reach those performances, but one of their major advantages is their indoor climate regulation capacity as well as their compatibility with vernacular buildings made with crude earth or limestone. The weaknesses of these materials are their poor mechanical performances avoiding any structural use and also their sensitivity to liquid water. In order to enhance both characteristics, ethyl silicate tends to offer interesting guarantees as an additive that need to be further studied. On the contrary, an addition of a low amount (5%) of lime is counterproductive, decreasing both mechanical and capillarity resistance. Masons use to recover those kind of insulating materials with a finishing plaster, we then found interesting to measure the impact of this coating on the MBV and acoustical (absorption and transmission loss) performances of the biocomposites. It appears that the influence of those coating decrease hydric dynamical regulation and the sound absorption but enhance the transmission loss. Lastly, we investigate the behavior of the thermal flow through a limestone wall covered with a clay:rape-straw plaster in a climatic chamber. We compared the found results with a WUFI 2D software simulation and tried to also simulate the changes in the drying kinetic of a fresh composite covered with different kinds of finishing plasters pointing the important drying delays depending on the coating used. One of the main interests of this study is to confirm that a wide range of locally produced vegetal byproducts could be used as bioaggregates for concretes. Local biomaterials industries could therefore emerge depending on the locally available resources at country scale. Despite its lower mechanical performances and vulnerability to liquid water compared to lime or pozzolanic binders, the use of crude earth as binder for vegetal concretes deserves further studies. Besides its ecological and hygrothermal performances, clay production is practically ubiquitous, enabling the emergence of very local clay-vegetal aggregate concrete industries to develop a green, carbon-light and circular economy.
... Dans le cas d'enduits isolants, le matériau devra au minimum supporter son poids propre, la norme allemande DIN 4108-10 concernant les matériaux d'isolation thermiques manufacturés fixant la contrainte à atteindre en compression simple à 0,02MPa.La quantité d'eau présente à l'instant t dans un matériau d'isolation impacte sensiblement ses performances thermiques, les concepteurs peuvent chercher à profiter de cette caractéristique et favoriser l'absorption de vapeur d'eau avec pour objectif de lisser les pics d'humidité à l'intérieur des pièces d'un habitat pour en augmenter le confort et profiter des effets thermodynamique liés à la condensation et l'évaporation de vapeur d'eau dans les matériaux engendrant des phénomènes passifs de climatisation. La connaissance des propriétés hydriques de ces matériaux est par conséquent nécessaire pour l'interprétation de ses performances.La connaissance des phénomènes de capillarité propres aux matériaux d'isolation à base de végétaux est également cruciale car outre les performances thermiques fortement dégradées d'un matériau poreux imbibé d'eau, lorsque le liant utilisé est à base de terre-crue, la dégradation des propriétés mécaniques est un risque élevé menaçant l'intégrité du matériau et enfin, le risque d'un développement de moisissures comme cela a été constaté sur des bétons de chanvres exposés aux intempéries(Jay et al. 2017) avec des conséquences néfastes pour l'aspect sanitaire de la qualité de l'air intérieur.Optimiser les matériaux à base de terre-crue pour améliorer leurs performances mécaniques et diminuer leur sensibilité à l'immersion est devenu un axe de recherche pour l'amélioration des techniques de construction à base de terre crue. L'emploi d'additifs est une piste d'optimisation des mélanges terre-végétaux qui a été investiguée également ici de manière exploratoire et qui demanderait une étude plus approfondie dans un avenir immédiat ; de même l'empreinte environnementale engendrée par la stabilisation est questionnée. ...
... Ces simulations permettent également de mettre en avant que la durée de séchage de l'isolant biocomposite recouvert d'un enduit de finition à base d'argile est deux fois et demie plus importante que celle sans enduit. Toutefois, il a été constaté par Jay et al.(Jay et al. 2017) que la mise en place ou non d'un enduit de finition sur des blocs de chaux-chanvre non secs a un impact moindre sur la durée de séchage. La diminution de la période de séchage étant un facteur essentiel pour éviter l'apparition de moisissures dans l'isolant bio composite, une attention particulière doit être apportée sur le type d'enduit de finition à utiliser (ou son absence) au moment de la mise en oeuvre. ...
Thesis
Full-text available
Le secteur du bâtiment est une source majeure d'émissions de CO2 dans le monde (à la fois pour la construction et l'exploitation des bâtiments), en raison notamment de la consommation d'énergie (chaleur, ventilation et refroidissement) et de la production de matériaux. Parallèlement à cela, l'épuisement des ressources naturelles tend à devenir un problème critique. Parmi les réponses pouvant être apportées pour faire face à ces défis, l'utilisation de ressources renouvelables et recyclables, à faible énergie grise apparait pertinente. À cet égard, l'utilisation de co-produits agricoles en tant que granulats légers à des fins d'isolation thermique est une solution méritant d’être étudiée. Ces matières premières génèrent une faible énergie grise et peuvent être considérés comme des déchets avec un bilan carbone positif car ils stockent du CO2. La substitution de la chaux ou du ciment par de la terre crue locale améliore également sensiblement l'empreinte carbone d’un matériau de construction. Le travail présenté ici qui a pour objet de mesurer les performances de ces matériaux respectueux de l'environnement a été réalisé dans le cadre du projet BIOCOMP ayant pour but de développer des biocomposites produits localement ayant pour vocation d’être utilisés en tant que matériaux isolants intérieurs. L’intérêt pour les partenaires du projet est d’offrir des solutions de rénovation pour les bâtiments vernaculaires de Touraine. Dans cette étude, des échantillons ont été préparés en utilisant 4 granulats végétaux différents (paille de colza, écorce de tournesol, moelle de tournesol et mélange de moelle et d'écorce de tournesol) avec une terre crue servant de liant pour un même rapport liant / granulats.Cette étude a pour objet de comparer les propriétés acoustiques, mécaniques et hygrothermiques de différents biocomposites à base de granulats issus de co-produits végétaux et d'argile. Nous avons d'abord analysé les matières premières afin d'obtenir d’une part la masse volumique et les propriétés thermiques et hydriques des granulats végétaux et les caractéristiques minéralogiques et gravimétriques de la terre crue sélectionnée d'autre part. L’évolution de la conductivité thermique des mélanges terre:granulats végétaux a été étudiée à différents taux d'humidité et différentes masses volumiques. D’un point de vue hydrique, les capacités de sorption/désorption de ces matériaux ont été mesurées en régime statique de même que la capacité de tampon hydrique simulant un régime dynamique. La capillarité des granulats et des biocomposites a également été étudiée. L'étude de ces propriétés hydriques permet d’estimer l’adéquation de solutions de rénovation basées sur ces matériaux avec le bâti local constitué de pierres calcaires très poreuses possédant une forte capacité de réguler l’humidité. Les conductivités thermiques de mélanges de terre-crue: colza et terre-crue:tournesol (écorce et moelle) doivent être inférieure à 0,065W.m-1.K-1 pour que ces matériaux soient considérés comme isolant thermique de bâtiment selon la norme NF P 75-101. Les enduits chaux:végétaux ou terre-crue-végétaux peuvent difficilement atteindre ces performances, mais l'un de leurs principaux avantages tient à leur capacité de régulation du climat intérieur ainsi que leur compatibilité avec les caractéristiques des bâtiments vernaculaires. Le point faible de ces matériaux réside dans leurs faibles performances mécaniques empêchant toute utilisation structurelle ainsi que leur sensibilité à l'eau liquide. Afin d'améliorer ces deux aspects, l’ajout de silicate d'éthyle semble offrir des garanties intéressantes nécessitant la mise en place d’essais complémentaires. Au contraire, l'ajout d'une faible quantité (5%) de chaux est contre-productif, diminuant à la fois la résistance mécanique et la résistance à la capillarité. Lors de la mise en œuvre de ce type de matériaux isolants, les maçons ajoutent généralement un enduit de finition, il nous est par conséquent apparu pertinent de mesurer l'impact de ce revêtement sur les capacités de tampon hydrique et les performances acoustiques (absorption et affaiblissement) des biocomposites. Cette couche de finition diminue la régulation dynamique hydrique et l'absorption acoustique, mais augmente la perte de transmission. Pour finir, nous avons étudié le comportement du flux thermique à travers une paroi en pierre de tuffeau locale recouverte d'une couche isolante d’argile: colza placée à l’intérieur d’une chambre climatique. Nous avons comparé les résultats avec ceux obtenus via une simulation via le logiciel WUFI 2D. Ce logiciel nous a également permis de simuler l’effet de différentes compositions d’enduits de finition sur les capacités de séchage du biocomposite à l’état frais ainsi que les changements dans la cinétique de séchage d'un composite induisant des augmentations de la durée de séchage différentes selon le type d’enduit.L'un des principaux intérêts de cette étude est de confirmer qu'une large gamme de co-produits végétaux produits à l’échelle locale pourrait être utilisée en tant que granulats pour l’élaboration de bétons végétaux. Malgré ses performances mécaniques plus faibles et sa vulnérabilité à l'eau liquide par rapport aux liants à la chaux ou à la pouzzolane, l'utilisation de la terre-crue comme liant pour les bétons végétaux mérite d’être étudiée plus avant aux vues de sa forte disponibilité, de son bilan environnemental positif et de ses propriétés hygrothermiques. Des filières locales de matériaux biosourcés pourraient donc être mise en place sur de nombreux territoires en fonction des ressources disponibles localement permettant le développement d’une économie circulaire vertueuse pour l’environnement.
... The building and construction sector is responsible for 32% of global energy use and 19% of greenhouse gas emissions [4]. For this reason, the production and use of environmental-friendly building mate-materials in the design of environment-friendly buildings [8]. Environmental concerns about conservation of natural resources and sustainability have been a significant source of motivation for researchers to work on environment-friendly composite materials which contribute low environmental impact, long-term community benefits as well as profitability [9,10]. ...
... Minguela [61] observed that the thermal conductivity of earth blocks had been largely reduced after the addition of fine hemp shiv. Piot et al. [8] reported that using a water-absorbing exterior coating or plaster increases the thermal conductivity of the hempcrete wall. Another risk of using a water-absorbent coating is the growth of mold just below the coating. ...
Article
Full-text available
Background Environment-friendly materials attract attention whilst the construction sector causes excessive global energy consumption and emission of greenhouse gas. Renewable plant-based biomaterials, which have a low environmental impact, are very beneficial in order to prevent environmental pollution and to preserve natural resources. Hempcrete provides environment-friendly construction materials as well as thermal and hygroscopic properties. Objective This paper presents a review of hempcrete research about understanding the environmental effects and construction methods of hempcrete; moreover, the benefits and innovations it has provided throughout its life cycle, have been investigated. Methods For this purpose, experimental studies of hempcrete were compared to each other in all aspects in order to determine density, thermal conductivity, vapor permeability, hygrometric behavior, durability, acoustic absorption, mechanical properties and life cycle analysis. Moreover, binder characteristics, hemp shiv proportions, water content, curing conditions and results have been focused on to explain the benefits of hempcrete. Results The results obtained show that hempcrete has high porosity and vapor permeability, medium-low density, low thermal conductivity, Young’s modulus and compressive strength. Conclusion Based upon the findings of the studies reviewed, hempcrete is an advantageous material in buildings with its extraordinary thermal and hygrometric behaviour. Hemp is also an eco-friendly and economical plant-based raw material for the construction industry.
... The building and construction sector is responsible for 32% of global energy use and 19% of greenhouse gas emissions [4]. For this reason, the production and use of environmental-friendly building mate-materials in the design of environment-friendly buildings [8]. Environmental concerns about conservation of natural resources and sustainability have been a significant source of motivation for researchers to work on environment-friendly composite materials which contribute low environmental impact, long-term community benefits as well as profitability [9,10]. ...
... Minguela [61] observed that the thermal conductivity of earth blocks had been largely reduced after the addition of fine hemp shiv. Piot et al. [8] reported that using a water-absorbing exterior coating or plaster increases the thermal conductivity of the hempcrete wall. Another risk of using a water-absorbent coating is the growth of mold just below the coating. ...
Article
Full-text available
Background: Environment-friendly materials attract attention whilst the construction sector causes excessive global energy consumption and emission of greenhouse gas. Renewable plant-based biomaterials, which have a low environmental impact, are very beneficial in order to prevent environmental pollution and to preserve natural resources. Hempcrete provides environment-friendly construction materials as well as thermal and hygroscopic properties. Objective: This paper presents a review of hempcrete research about understanding the environmental effects and construction methods of hempcrete; moreover, the benefits and innovations it has provided throughout its life cycle, have been investigated. Methods: For this purpose, experimental studies of hempcrete were compared to each other in all aspects in order to determine density, thermal conductivity, vapor permeability, hygrometric behavior, durability, acoustic absorption, mechanical properties and life cycle analysis. Moreover, binder characteristics, hemp shiv proportions, water content, curing conditions and results have been focused on to explain the benefits of hempcrete. Results: The results obtained show that hempcrete has high porosity and vapor permeability, medium-low density, low thermal conductivity, Young's modulus and compressive strength. Conclusion: Based upon the findings of the studies reviewed, hempcrete is an advantageous material in buildings with its extraordinary thermal and hygrometric behaviour. Hemp is also an eco-friendly and economical plant-based raw material for the construction industry.
... The issue could be compounded further if a water-absorbing render such as lime plaster is applied to the walls. The external render was suggested to be water-resistant to prevent mold growth and improve durability (Piot et al. 2017). However, considering that the thermal capacity of hemp concrete increases with higher RH, the time taken to reach thermal equilibrium would be much longer. ...
... Phillip and De Vries [7] have developed a model basically for soil materials, this model took into account temperature gradients inside materials, it represents the origin of most new models, it was lately well studied and represented by Mendes et al. [8]. Kunzel et al. [9] have carried out a comprehensive parametric study of heat and mass transfers for the specific case of building materials, where his developed model was adopted by many works and gave satisfactory results [10][11][12]. In this work, we aim to validate Phillip & De Vries and Kunzel models by doing a confrontation against simulations performed on an already validated commercial simulation tool using a classic material, for a next work that will be dedicated to the use of these models for bio-based building materials. ...
Chapter
In this work, we study the two most used mathematical models (Phillip & De Vries model and Kunzel’s model) which describe heat and moisture transfers in porous building materials. These models were implemented in COMSOL Multiphysics and solved numerically with the finite elements method. To validate the representation of the physical phenomena made by the numerical models, results were compared with data obtained by Wufi using a concrete wall. The results indicate that values estimated by both models are relatively in good agreement with those obtained by Wufi especially for temperature, while in humidity variations an underestimation by Phillip and De Vries model was Highlighted. Consequently, results confirm the suitability of these models to be used in further studies in order to predict hygrothermal behaviors of bio-based building materials and walls under various thermal and hygric conditions at different scales.
... 167 Piot et al., 2017. 168 Chaban, 2015. ...
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Updated toolkit available at www.cannabis2030.org – También en español: www.cannabis2030.org/es –––––– Subtitled "Recommendations for the implementation of Cannabis policies aligned with international Human Rights standards, the 2030 Agenda for Sustainable Development and the 2016 UNGASS outcome document", this report explains how the reform of hemp and cannabis policies can sustain or make harder – depending on the policy options chosen – the attainment of the 2030 United Nations agenda for Sustainable Development. | The reformist trend in Cannabis policy globally is an ongoing movement unlikely to be stopped. A deficit of democratic monitoring of the generalization of legal Cannabis markets could represent a threat for affected populations and public health. Ethics are needed. A renewed interest and takeover of the topic Cannabis by all categories of the population are urgent. A one-size-fits-all policy seems neither desirable nor possible, both for geographical imperatives and for the diversity of uses and products of the plant. This makes consensual policy models (exportable and generalizable) difficult to emerge. Rather than trying to solve the equation of the perfect Cannabis policy and its infinite variables, a more feasible approach would be to step aside, list all the different public policies that affect, or are involved with Cannabis, and address them individually. The 2030 Agenda for Sustainable Development and its 17 Goals is but a perfect tool for this purpose. This discussion paper highlights important research and experiential outcomes from scholars, civil society organizations, affected populations, and market stakeholders. It seeks to show the potential of the Cannabis plant in appropriately regulated settings as transformative for our societies – so long as ethical practices and sustainable approaches are kept central. This document is not intended to be an exhaustive guide. It is designed as a valuable resource to contribute to post-prohibition studies, and help understand, from diverse public policy perspectives, the links between the policies of Cannabis and the Sustainable Development Goals, and the impact of the former on the latter. The latest updated 2021 version is available at www.cannabis2030.org
... Hemp lime composite owes its excellent thermal conductivity properties to high hemp shiv porosity [16]. Its properties attract even more people both in this country and abroad to launch investigations and promote hemp-lime composite applications in the construction of new or improving thermal insulation performance of the existing buildings [17][18][19][20]. ...
Article
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The main goal of the paper is to calculate the heat conductivity for three experimental hemp–lime composites used for structural construction purposes with the use of the experimental stand inside two compartments. Due to current construction trends, we are constantly searching for eco-friendly materials that have a low carbon footprint. This is the case of the analyzed material, and additional thermographic heat distribution inside the material during a fire resistance test proves that it is also a perfect insulation material, which could be applied in addition of popular isolating materials. This paper presents the results of certain hemp–lime composite studies and the potential for using hemp–lime composite for the structural construction industry. Hemp–lime composite heat transfer coefficient, fire resistance, and bulk density properties are compared to those of other commonly used construction materials. The obtained results show that the material together with supporting beams made of other biodegradable materials can be the perfect alternative for other commonly used construction materials.
... Hemp concrete or hempcrete has been employed increasingly as a 'green' building material in the past 1-2 decades (Bevan and Woollley, 2008). Similar to traditional structures, such as wattle and daub, it can be used to moderate the indoor temperature due to its hygrothermal responsiveness (Piot et al., 2017). It is a lightweight material which, as with traditional concrete, requires some reinforcement to be used as load-bearing, has a low CO 2 -footprint and can be made from wholly renewable material (Gołębiewski, 2017). ...
Preprint
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This work presents a comprehensive review of how the landscape of fire safety challenges of ‘green’ attributes of buildings has developed since 2012. It is based on a global information search into: fire events involving ‘green’ and/or sustainable building materials, systems and features; emerging ‘green’ building materials, systems and features; and research, regulatory changes, engineering approaches, risk mitigation strategies, and firefighting tactics associated with fire challenges with ‘green’ and/or sustainable building materials, systems and features. While the research is comprehensive is scope, it is not exhaustive in detail, given the extent of advancement in these areas which has occurred since 2012. And, while significant advancements have been made, gaps remain, and strategies for proactively incorporating fire performance into development of new ‘green’ building materials, systems and features (product development) are lacking, the tools to proactively assess the fire performance of ‘green’ building materials, systems and features at the product level (e.g., fire performance testing), and as installed in buildings, are lacking, and a broader building regulatory framework and design philosophy for achieving sustainable and fire resilient (SAFR) buildings is also lacking. Based on the overview conducted and the analysis undertaken, a set of recommendations for future work to address gaps and to advance the concept of SAFR buildings and communities have been identified.
... The behavior of this material in different climatic conditions and its properties have been considered in numerous studies [8]. Different characteristics of hemp as a building material, including its thermal characteristics as well as the properties of hempcrete with several binders have been investigated [9,10]. ...
Article
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Nowadays, sustainable construction is a key factor for reaching net-zero emissions of carbon dioxide all over the world. This goal is impossible to achieve by merely reducing the energy consumption of end-users. A more holistic approach should be taken, adopting sustainable industrial practices that use environmentally friendly materials on a large scale. This paper presents the analysis of the hydrothermal properties of hemp thermal insulation plates. We carried out extensive measurements and the analysis of the thermal conductivity coefficient, drying-out dynamics, and water absorption. The study was performed with experimental insulation samples based on the fiber obtained from hemp stems, prepared using different adhesive powders. The dimensions of the analyzed samples were 300 × 300 mm. The proposed samples are not yet available in mass production. Hemp does not flower in the Baltic region and was traditionally used for soil regeneration. Thus, using this raw material increases the added value of agricultural residues. Three series of hemp fiber samples with different substances and pressing modes were evaluated in the study. Each set of samples consisted of four plates with varying thicknesses and two different densities: 200 kg/m3 and 300 kg/m3. All samples exhibited a significant increase in moisture absorption and a strong correlation with the increase in thermal conductivity. The average thermal conductivity of the test samples ranged from 0.0544 to 0.0594 W/mK. The impact of the adhesive powder on the thermal conductivity was found to be extremely small. However, the values obtained were much higher than those for traditional thermal insulation materials, allowing to utilize the local agriculture residues and providing material for the construction of eco-friendly buildings.
... The hemp-based insulating material thus better regulated the indoor air environment by moderating changes, which is likely to translate to reduced need for air conditioning, and ultimately energy savings. Extensive research has been carried out with similar hemp-lime wall assemblies for internal partitions [3,7,[12][13][14][15][16][17][18]. In the example of a hemp-lime assembly, protection against biodegradation is offered via the highly alkaline lime present [18]. ...
Article
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New bio-materials have recently gained interest for use in insulation panels in walls, but wider adoption by the building industry is hindered by their intrinsic properties. The fact that such materials are mainly composed of cellulose makes them combustible, and their hydrophilic surface presents a high water uptake, which would lead to faster biodegradation. A hydrophobic treatment with silica particles was successfully synthesised via Stöber process, characterised, and deposited on hemp shiv. The surface of hemp shiv coated several times with 45 and 120 nm particles were uniformly covered, as well as extensively water repellent. Those samples could withstand in humidity chamber without loss of their hydrophobic property and no sign of mould growth after 72 h of exposure.
... In addition, the measurement of thermo-hygrometric properties is fundamental to determine the response of the material to variations of temperature or relative humidity. If these tests are performed in situ, the efficacy of the material and of the selected coating can be determined in the climatic conditions of application as well as the effect on the indoor comfort can be evaluated [14][15][16][17]. Hence, the modelling of hygrothermal behaviour is crucial to predict the behaviour of the material when different constructive strategies are applied, e.g. ...
Article
In the framework of Circular Economy policies aimed at reducing the consumption of raw materials, shives, an agricultural by-product of hemp cultivation, have gained a renovated life in the construction sector; new building materials, suitable for various executive techniques, have been developed exploiting the excellent thermal insulating properties of shives. When this vegetal material is mixed with a mineral binder such as lime or cement, the mixture is usually referred to as hemp-lime. In Italy, the use of hemp-lime blocks and the development of new production chains dates back only to about the last decade, while other European countries have more long-lasting experiences. In order to assess the potential benefits of hemp-lime blocks in the construction sector, it is necessary to evaluate the performance of these materials in situ, i.e. on the construction site, to obtain fundamental data to ensure that consumers and designers receive trustworthy and relevant information on products and their durability. This research work aims to be a solid base for the development of future guidelines and/or regulations at national and international level, in order to guarantee the maximum diffusion of this type of product. Then, a study plan has been carried out regarding the functionality of hemp-lime blocks in masonry, layered with finishing plaster made of fine hemp shives, to evaluate the in situ thermo-hygrometric building performance. In particular, experimental methods were developed and measurements were carried out on two structures, one in northern Italy and one in southern Italy, and precisely in Sicily, focusing the study on the performances of the walls subjected to warm Mediterranean climates.
... Hemplime composite, been regarded as one of the possible sustainable replacements or supplements to traditional thermal insulation materials [1], is yet to be properly evaluated. Various studies [2][3][4][5] were usually based on pointing the possible scope of properties of hempcrete depending on both mixture composition and method of sample preparing. As previous research [6] have already shown the best way of obtaining material with desired attributes, it seems vital to focus on assessing specific hempcrete mixtures by their usability. ...
Chapter
One of the most important issue in multicriteria assessment is finding proper way of criteria weights estimation. It is especially problematic in assessment of newly introduced building materials, when almost none historic data is available. In this paper various methods of weights estimation are compared in valuation of various HLCs (Hemp-lime composites), commonly referred to as hempcrete. New method based on standard deviation of ratings in each criterion is proposed and compared with traditional, well-known algorithms such as Simos method, both variants of calculation proposed by Hokkanen and Salminen and REMBRANDT system.
... In some cases, plant biomass is advantageous to use because of its low production cost, fast growth, and self-sustaining character due to the quicker renewability of their source. The speed of their growth shows very promising results from an environmental impact and commercial point of view if the proper technological application is utilized [10,[13][14][15][16][17]. ...
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Research was performed into the use of hemp shive as a fast-growing and carbon-storing agricultural waste material in the production of particleboard for the construction industry. Hemp shives were acquired and prepared for board production with the use of milling and sieving to reach two target groups with 0.5 mm to 2 mm and 2 mm to 5.6 mm particle size ranges. The cold pressing method was used to produce hemp boards with Kleiberit urea formaldehyde resin as a binder. The boards were made as 19 mm thick single-layer parts with a density range of 300 ± 30 kg/m3, which qualifies them as low-density boards. Exploratory samples were made using milled hemp fibers with higher density. Additional components such as color pigments and wood finishes were added to test improved features over raw board samples. Tests were performed to determine moisture contents, density range, structural properties, and water absorption amounts. Produced board bending strength reached 2.4 MPa for the coarser particle group and thermal conductivity of 0.057 ± 0.002 W/(mK). The results were compared with existing materials used in the industry or in the development stage to indicate options of developed board applications as indoor insulation material in the construction industry.
Article
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The negative impacts of cement-based material (CBM) production are way bigger than ever expected. To illustrate the scale of this phenomenon, all the forests in the world, regardless of the fact that they are disappearing at an alarming rate, are not enough to offset even half the environmental impact (EI) of global aggregates and cement production. Thus, it is necessary to promote scientific research and guide more researchers and professionals in the construction industry to investigate the undiscovered sustainability paths, namely for concrete before and after end-of-life. For that purpose, a global and extensive review is made here to provide an overall view of concrete sustainability in all possible paths. Then, each path is organized as follows: (i) brief introduction, (ii) presentation of non-traditional materials and techniques that can be used for the selected strategy, (iii) their limitations and (iv) future trends. The study also identifies what is already known to avoid putting valuable research resources into redundant scientific studies. The following paths of concrete production sustainability were identified: mix composition (e.g. reduce the EI and resources use of binders, aggregates, water and reinforcement), materials manufacturing (e.g. new production techniques of cement, aggregates and steel bars), concrete mixing (e.g. mixer type and mixing method), on-site application (e.g. regular casting and digital concrete/3D printing), and in-service performance (e.g. increase the durability of reinforced concrete and carbon capture and thermal conductivity). On most of these paths, many studies have been made on the same non-traditional materials and techniques and similar outputs were obtained. Yet, many other non-traditional materials and techniques have not been explored before, or are incomplete in terms of the characteristics analysed. More than providing definite solutions, this contribution intends to open the minds of the readers to the vastly unexplored world of “green concrete”.
Article
Biobased composites are widely used for building insulation because of their hygrothermal performance, and their economic and environmental benefits. Among the different types of organic fibers for these materials, hemp shives are interesting because of their high availability in France and their low price. Nevertheless, the wide application of the hemp-based insulation mortars is hampered by the lack of data on its durability and behavior over the long term. The objective of this study, in a first part, consists in providing an original accelerated aging protocol inspired by the standardized one used for External Thermal Insulation Composite Systems (ETICS). In a second part, the selected aging weathering cycles were applied to investigate the hygrothermal stresses on the morphology, chemical composition and properties of hemp mortar samples. Experimentally, microstructural characteristics (as total porosity, SEM observation) and hygrothermal properties (as thermal conductivity, Moisture Buffer Value (MBV) and water vapor permeability) were measured and evaluated for both the reference state (after 28 days of conditioning) and after aging (after 28 days of conditioning and the aging cycles). Furthermore, X-ray diffraction and PH analysis were performed to investigate the chemical composition, especially the effect of carbonation. The obtained results reveal the presence of two processes in the aged hemp mortars: the carbonatation of the mineral matrix and the cracking of the interface between the hemp shives and the cement matrix. This later was quantified too. Despite the microstructural degradation, small deteriorations were recognized concerning the hygrothermal properties and behavior of hemp mortar, that is essential for an insulation material. These results provide data for better forecast on the degradation of the hemp mortars.
Article
Bio-based building materials are composites of vegetal particles embedded in an organic or mineral matrix. Their multi-scale porous structure confers to them interesting thermal, hygroscopic and acoustic properties. These performance properties have spurred research on these materials as alternative building materials with low embodied energy. This review contains a comprehensive critical analysis of mechanical, thermal, and acoustic properties of bio-based building materials with a particular focus on the interactions of various constituents and manufacturing parameters. Alkali-activated binders are reviewed for their potential use in high strength bio-based composites. A detailed physico-chemical characterisation of the aggregates and compatibility analysis allow a comprehensive understanding of fundamental phenomena affecting mechanical, thermal, and acoustic properties of bio-based building materials. A wide range of biomass materials is available for building composites, and hemp shives remain the most prevalent bio-aggregate. In the context of England, the farming of industrial hemp remains limited, due in part to the long, costly licencing process and the abandonment of processing subsidy as part of the EU common agricultural policy in 2013. On the other hand, Miscanthus (elephant grass) is a perennial, low-energy, and well-established crop in the England which is gaining interest from farmers in the South West region. Its development aligns with actual agricultural, land management and environmental policies with potential to fuel innovative industrial applications. This review performs a critical assessment of the performance of bio-based materials in an attempt to identify potential frameworks and opportunities to develop building insulating materials from miscanthus.
Article
The present work proposes a generalized method for designing moldable bio-concretes, incorporating three types of vegetable residues (wood shaving, bamboo particles and rice husk) which are employed as bio-aggregates within a cement-based matrix. The above-mentioned procedure is based, first of all, on a fundamental physical and morphological characterization of the bio-aggregates as well as on the analysis of their compatibility with cement-based matrices. Then, considering the specific features of the employed bio-aggregates, a novel approach is also presented for the mixing production process of bio-concretes mixtures with the aim of warranty an adequate consistency and easy moldability at the fresh state. Finally, a comprehensive experimental campaign is performed with the aim of analyzing the influence of bio-aggregates on the bio-concretes performances at hardened state. The analysis proposed herein unveils the existing relationship between compressive strength, water-to-cement ratio, cement consumption and bio-concrete density leading to a proposed simplified design abaci. Considering the rational nature of the proposed approach, it can be easily extended to others kind of bio-aggregates that could be considered for producing workable bio-concretes.
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At present buildings contribute a third of total greenhouse gas emissions. There is a need for sustainable solutions and natural materials, which offer low-embodied energy and their low impact has a promising potential as construction alternatives. Hempcrete is a lightweight insulation material, which provides natural, airtight, and vapor-permeable insulation. Straw panels are also natural construction materials and they consist of extruded wheat straw and are surrounded with recycled paper on all sides. There are some risks, which can be associated with the use of such materials - infestation, biological degradation, presence of moisture, and structural degradation. The aim of the study is to determine the critical moisture level and mould resistance of hempcrete and straw panels. The results of this study are valuable to both scientists and structural engineers.
Article
Straw concrete is a biobased composite developed for thermal insulation of new buildings and thermal rehabilitation of old buildings. It is made of the combination of wheat straw, lime or plaster binder and natural additives (hemoglobin, casein, gelatin). The natural additives are used to improve the thermal and mechanical properties of the material. The characterization of these composites has shown an attractive thermal conductivity and an acceptable mechanical strength. The present paper focuses on the hygric characterization of these materials which have different constituents (straw aggregates, binder and additives). Three properties were experimentally determined, namely, sorption–desorption curves, water vapor permeability and moisture buffer value (MBV). These hygroscopic properties are of great importance when it comes to the comfort of the building. The isothermal water vapour diffusivity was also estimated from the sorption curve and the water vapor permeability. The impact of the sample thickness on the moisture buffer value (MBV) was also highlighted. The results showed that the studied composites have excellent hygric properties which can contribute significantly to ensure hygrothermal comfort in buildings. These hygric performances are competitive with those of other insulating bio-based materials studied in the literature and better than those of conventional materials used in construction.
Conference Paper
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In recent years, several studies on the durability of cementitious materials combined with vegetable fibers have been developed. In order to understand the properties of these materials in different environmental conditions, they can be subjected to accelerated aging through several cycles of controlled variations of humidity-temperature, wetting-drying, freezing-thawing. However, analyzes that expose such materials to real conditions of use during their useful life are scarce. As a result, this study analyzed the physical, thermal and mechanical behavior of bamboo bio-concretes produced with different volumes of bio-aggregates, which were exposed to the natural aging of the summer in the city of Rio de Janeiro (Brazil). The cementitious binder was is composed, by mass, of cement (30%), metakaolin (30%) and fly ash (40%). The water-to-cement ratio was as 0.30. The mixtures were produced with bamboo volumetric fraction of 30%; 40% and 50%. After 3 months of natural aging during the Brazilian summer (from December to March), the property determined in the hardened state was the compressive strength. In addition, a visual analysis by photograph was also realize. The results revealed that higher the volumetric fraction, higher the decrease of compressive strength. The visual analysis showed several changes of the external aspect of the bio-concretes.
Article
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Hempcrete is a very promising bio-based insulating material with a minor or even negative CO2 footprint and low thermal conductivity. To utilize it efficiently, it must be possible to make predictions regarding hempcrete hygrothermal performance and whether it is up to the modern standards—this requires a verified material model for use in numerical simulations. The results of ∼8 months of in situ temperature and relative humidity monitoring for a hempcrete wall are presented along with a documented manufacturing process, and the experiment is reproduced in silico, obtaining good agreement and observations in line with previous studies. Given the scarcity of in situ studies, the presented data could be used as a reference for simulations of moisture and heat transfer in building envelopes that contain hempcrete. Validation for hempcrete as a good insulating material for Latvian or similar climate conditions is also provided. Its high mold growth resistance even at high humidity is experimentally demonstrated. Combined with good water and vapor conductivity, this leads to consistently low mold growth risk as shown experimentally and in simulations.
Article
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Internal thermal insulation composite system (ITICS) can be an important measure for the energy-saving retrofitting of buildings. However, ITICS may cause harmful effects on the hygrothermal performance of building envelopes. This work investigated the influence of the materials' hygric properties on the hygrothermal performance of a typical ITICS in different climate conditions in China. Two base wall materials, the traditional concrete and a new type aerated concrete, were tested and compared for their hygric properties firstly. The influence of the hygroscopicity of exterior plasters, the permeability of insulation materials and the climate conditions were then analyzed with WUFI simulations. The hygrothermal performance was evaluated with consideration of the total water content (TWC) of the walls and the moisture flux strength, the relative humidity (RH) and the mould growth risk at the interface between the base wall and the insulation layer (B-I interface). The numerical analysis implies that the TWC of internal insulated walls depends mainly on the hygroscopicity of exterior plaster and the wind-driven rain intensity. The upper limits for the water absorption coefficient of exterior plasters used in Beijing, Shanghai and Fuzhou are 1e-9, 1e-10, 1e-10 m²/s respectively. When such limits are guaranteed, a vapour tight system created by using insulation materials with a large vapour resistance factor or adding a vapour barrier can improve the hygrothermal performance of ITICS, especially for concrete walls in cold climate.
Chapter
One of the key drivers of the alarming increase in anthropogenic carbon emissions is the construction industry and the built environment. Conventional building materials are harmful to the planet because of non-renewable resources and energy-intensive manufacturing processes. Conventional insulation materials, masonry materials, and concrete are highly polluting and cause significant amounts of damage to the global environment. Researchers have recently started studying natural alternatives to overcome the current materials’ environmental challenges and functional disadvantages. Hemp has emerged as a resource with immense potential because of its renewability, ease of cultivation, and low maintenance as an agricultural crop. Many applications of hemp were also found in ancient and modern history before it was replaced with petroleum-based products that were easy and faster to produce. Also, it has found renewed interest amongst the scientific community because of its beneficial properties such as tensile strength, thermal insulation, and lightweight. Many new applications have emerged, such as insulation mats, fiber-reinforced cement concrete, walling material, polymer composites, boards, etc. This chapter synthesizes the research on hemp’s construction applications, namely, hemp insulation mats, hemp fiber-reinforced concrete, and hemp concrete.
Article
This paper evaluates two types of concrete with hemp fibres as natural aggregates prepared with inorganic binders, based on reactions (Si-Na) and (Si-Ca). It also was tested two states of conservation of the hemp: 1) fresh and 2) preserved in moist conditions for six months. The results indicate that the changes induced by wet preservation, above all the increase in the percentage of cellulose, improve the mechanical properties of the concretes and is equivalent to other pretreatments conducted to improve the conditions of the hemp fibres confirmed by performing compositional, mineralogical and physical studies of the raw materials and the concretes. The dosages used in this study provided high quality concretes in comparison with other studies with similar dosages.
Chapter
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This paper compares the properties of hemp concrete made with hydrated lime and pozzolan with those of composites made with commercial binders containing hydraulic additions, in an effort to make hemp concrete more sustainable. The binder type affects the properties and microstructure of hemp concrete. The results indicate that increasing the binder’s hydraulicity enhances compressive strength and lowers capillary action. As in lime and cement-lime mortars, this is probably due to the presence of hydrates. Despite the high hydraulic content of the commercial binder evidenced with Scanning Electron Microscopy, the ultimate strength of the commercial concrete is similar to that of the lime-pozzolan concrete. The commercial composite did not reach its full potential strength due to the strong hydraulic nature of its binder and the competition for water with the hemp. The paper also concludes that, initially, composites including highly hydraulic binders dry faster however, at later ages, composites with hydrated lime binders dry faster. The slow early drying of the lime is likely due to its high water retention while drying becomes faster at later ages due to its higher permeability.
Conference Paper
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The aim of this work is to understand the hygrothermal behaviour of hempcrete based on cement at a wall size level. For this both simulation and experimental measurements are conducted in parallel. In the experimental study two Passys test cells are used to compare 2 test walls, subjected to weather solicitations outside and hygrothermal regulation inside. The only difference between walls is the coating, in order to analyse its effect on moisture transfer: one cell is supplied with traditional lime render and the other one with industrial, cement based render. The ability of the coating to regulate relative humidity is shown in this paper. Simultaneously the numerical study is used to calibrate a model to this material in order to have a more complete understanding than the experimental study. A parametric study on material parameters is done to emphasize the impact of coatings, and to analyse the effect of material characteristics’ variation on global behaviour. For this, a coupled heat and moisture transport model is applied with boundary condition from the monitored data (outside and inside). This study show that the hempcrete is sensitive to the applied coating’s properties: in particular, the exterior coating must protect from rain absorption, and be permeable to vapour, otherwise the moisture inside the hempcrete rises, which can reduce the wall performances.
Conference Paper
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The use of bio-based materials in construction is significantly improving. One of the bio-based materials is hemp concrete which is a composite obtained by mixing a binder and the nonfibrous part of hemp, called shiv. This specific hemp concrete developed by Vicat is made with Prompt Natural Cement (PNC). Hemp concrete is used for its insulating properties and its capacity to control humidity which is obtained due to the hydrophilicity of shiv. Therefore to reach the same level of binder hydration more water is needed in hemp concrete than in traditional concretes. This excess of water combined with insufficient drying of hemp concrete may quickly lead to the development of mould. In fact, the binder alkalinity is not sufficient to stop the microorganism development. This study presents results from two tests to quantify mould development in PNC-based hemp concrete. The first series of test was carried out respectively on the shiv only and on hemp concrete specimens which were a few hours and a few days old. During the first 24 hours the number of microorganisms identified on hemp concrete specimens decreases more significantly than on the raw shiv. So the hemp concrete formula prevents concrete from developing mould. A second part of the study was carried out on a hemp concrete of same formula than previously but coated with two different renders: one coating permeable to both liquid and vapour water while the second one is permeable to vapour water but not to liquid water. The coated hemp concretes had been exposed to external conditions for four seasons. After one year, some samples were removed in order to study the microorganism development. The tests show that the exterior coating must be well chosen. Using a waterproof coating which is permeable to moisture does not present development of mould.
Conference Paper
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The use of bio-based materials in construction is significantly improving. One of the bio-based materials is hemp concrete which is a composite obtained by mixing a binder and the non-fibrous part of hemp, called shiv. This specific hemp concrete developed by Vicat is made with Prompt Natural Cement (PNC) as binder. In situ hygro-thermal performance assessment of this material was performed in this paper. For this both simulation and experimental measurements are conducted in parallel. In the experimental study two PASSYS test facilities are used. They are parallelepiped test cells around 30 m3 volume each. One test wall is built with the interesting façade while the five other walls are highly insulated and are non-tested walls. Test walls are subject to weather solicitations outside and hydrothermal regulation inside. The two test cells are next to each other, and the hempcrete wall is south oriented. The only difference between cells is the external coating in order to analyze the coating effect on moisture transfer: one cell is supplied with traditional hemp lime render and the other one with cement based render. In parallel, 2D numerical simulation of hygrothermal behavior of the wall was carried out using a coupled heat and moisture transport model with boundary condition from the monitored data (outside weather conditions and inside regulation). Results show a good agreement between measured and simulated data.
Article
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Experiments were carried out according to the Nordtest protocol to study the moisture buffer potential of hemp-lime walls with a range of different internal linings and surface treatments. It was observed that the moisture buffer value was ‘Excellent’ when the inner surface of hemp-lime was exposed. ‘Excellent’ moisture buffer values were also obtained for hemp-lime with lime plaster. All other assemblies demonstrated ‘Good’ moisture buffer value. Moisture buffer values of the assemblies, after application of paint on the upper surfaces, were also determined. It was observed that application of synthetic pigment based trade paint could reduce the moisture buffer performance of the assembly consisting of hemp-lime and lime-plaster from ‘Excellent’ to ‘Good’ while between 61 and 69% reduction of moisture buffer value was observed for the other assemblies. However, the reduced buffer values of the assemblies are still comparable with other moisture buffering building materials. It was further observed that moisture buffer performance was improved when clay based organic paint was used instead of trade paint.
Conference Paper
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Alternative products such as green materials are either back or newly implemented in the construction field. The low environmental impact of hemp concrete and its thermo-hydric behaviour show the possibilities of healthier construction and let obtain a better comfort of users. In contrast with usual concrete, the hemp concrete has huge hygroscopic buffer capacity. The aim of this work is to study the hempcrete with prompt natural cement, which is a concrete block made of a mixture of hemp shivs and "Prompt natural cement". For that, its behaviour in energy consumption and comfort at a wall and building size level are analysed thanks to simulation and experimental measurements, which are conducted in parallel. Experimental tests have been run at wall scale in two PAS SYS test facilities. Test walls are subject to weather solicitations outside and hydrothermal regulation inside. For numerical study, a 2D coupled heat and moisture transport model is defined. Numerical analysis gives results in the same trends as experimental data.
Article
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Lime-hemp concrete (LHC) is a sustainable building material that combines hemp shiv and building limes. Moisture fixation and thermal properties of LHC were determined so as to gain knowledge about the material's behaviour in a cold, wet climate. Sorption isotherms were produced over the whole moisture range for two LHC mixes by means of glass jar tests and a pressure plate apparatus. Thermal properties were determined for the mixes at different relative humidities using a transient plane source method. The results showed relatively low thermal conductivity and a steep sorption isotherm in the interval between 95% and 100% RH.
Article
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Performance and service life of building components are to a large extent determined by their hygrothermal behaviour. Since experimental examinations, apart from being expensive, can cover only small aspects of the real phenomena, the demand for computational tools has increased in recent years. In contrast to previous moisture calculations depending on sophisticated material parameters which were difficult and sometimes impossible to measure, new investigations have led to rather simple yet very accurate models requiring mostly standard material properties. Numerous applications have already proven the validity of the described calculations, which are based on physically plausible formulations.
Patent
The present invention relates to a novel construction material including: 10% to 60% of a hydraulic binder and/or an air-cured binder; 16% to 50% of a plant-based aggregate; 0.05% to 5% of a water-retention agent; and 10% to 50% of water. The invention also relates to a kit which is useful for preparing such a construction material.
Article
An in situ experiment on a full-scale timber frame test building was carried out to study the hygrothermal performance of wood-hemp composite insulation in timber frame wall panels with and without a vapour barrier. The heat transfer properties and the likelihood of mould growth and condensation in the panels were compared. Step changes in the internal relative humidity were performed to explore the effects of high, normal and low internal moisture loads on the wall panels. No significant difference in the average equivalent thermal transmittance (U-values) between the panels with and without a vapour barrier was observed. The average equivalent U-values of the panels were close to the U-values calculated from the manufacturers’ declared thermal conductivity values of the insulation. The likelihood of condensation was higher at the interface of the wood-hemp insulation and the oriented strand board (OSB) in the panel without a vapour barrier. In terms of the parametric assessment of the mould germination potential, the relative humidity, the temperature and the exposure conditions in the insulation-OSB interfaces of the panel without a vapour barrier were found to be more favourable to the germination of mould spores. Nonetheless, when the insulations were dismantled, no mould was visually detected.
Article
Over half of the global raw materials are consumed in the construction of buildings and roads, their associated greenhouse gas emissions from excavation to final disposal are pivotal to the change in global climate. Hemp is a natural resource that has recently been used as a low environmental impact material in a number of composite products. In buildings, it is increasingly used with a lime base binder in wall constructions. There are limited data available to evaluate the environmental impact of this type of construction in the UK. This research aims to identify the processes and materials involved in the construction of hemp-lime walls and to establish their life cycle impact on climate change. The study follows assessment procedures and guidelines of international (ISO14040) and UK (PAS2050) standards. The functional unit defined for the hemp-lime wall construction is 1 m square in area, 300 mm thick with timber frame support inside. Primary data were collected for processes and materials that have no existing information. Other processes with impact data available from credible database were adapted in the assessment by taking into account the conditions and practice in the UK. Assessment was carried out using the SimaPro LCA tool over a lifetime of 100 years. Within the boundary and assumptions made, results showed the functional unit could sequestrate 82.7 kg of carbon dioxide with a net life cycle reduction of greenhouse gas emission of 36.08 kg CO2e. Crown Copyright
Article
This study investigates the hygrothermal behaviour of a timber-framed hemp concrete wall made of precast blocks. Measurements are performed on an uncoated wall as well as on a coated wall. The experimental device consists in two air-conditioned rooms where ambient conditions are selected to induce temperature and/or vapour pressure gradient between the two sides of the wall. The monitoring deals with temperature and relative humidity within the wall. Kinetics of temperature and of vapour pressure are given. Profiles are drawn at several times of the transient phase. In the regular part of the wall, several kinds of hygric behaviours are highlighted such as homogeneous vapour diffusion and huge vapour pressure variations due to evaporation–condensation and/or sorption-desorption phenomena. The results in the line of frame show that the frame doesn't induce disturbances in the hygrothermal behaviour of the wall. It is also shown that the coating reduces and delays vapour diffusion.
Article
This study investigates the effect of formulation, density and water content on the thermal conductivity of hemp concretes. The investigations are based on experimental measurements and on self-consistent scheme modelling. The thermal conductivity of studied materials ranges from 90 to 160 mW/(m.K) at (23 degrees C; 50%HR). The impact of density on thermal conductivity is much more important than the impact of moisture content. It is shown that the thermal conductivity increases by about 54 % when the density increases by 2/3 while it increases by less than 15 % to 20 % from dry state to 90%RH.
Article
This study deals with dynamic characterization of hydric behaviour of sprayed hemp concrete. The measurement of moisture buffer value (MBV) is held according to the NORDTEST protocol (Rode, 2005). Specimen are exposed to daily cyclic variation of relative humidity: 8 h at 75%RH and 16 h at 33%RH the test is held under isothermal conditions (23 °C). The experimental set-up is validated by comparison of moisture buffer value measured on cellular concrete with values given in the NORDTEST project for the same kind of material. Results show that sprayed hemp concrete has an excellent moisture buffer capacity (MBV = 2.15 g/(m2 %RH)). So, it is an excellent hydric regulator that improves hygrothermal comfort and reduces energy needs. Moisture effusivity is then calculated from sorption and water vapour permeability value and from dynamic test of MBV. The results (respectively 5.8 × 10−07 and 4.8 × 10−07 kg/(m2 Pa s1/2) show a slight discrepancy between values obtained from steady-state and from dynamic conditions. Finally, the penetration depth for daily cyclic variation is estimated about 5.8 cm for sprayed hemp concrete. Also, the experimental data set can be used for benchmarking buffering models.
Article
A detailed Life Cycle Assessment (LCA) has been conducted on a low energy family house recently built in Northern Italy. The yearly net winter heat requirement is 10 kWh/m2, while the same unit with legal standard insulation would require 110 kWh/m2. As the building was claimed to be sustainable on the basis of its outstanding energy saving performances, an ex post LCA was set up to understand whether, and to what extent, the positive judgement could be confirmed in a life cycle perspective. The dramatic contribution of materials-related impacts emerged. The shell-embedded materials represented the highest relative contribution, but maintenance operations also played a major role. The contributions of plants, building process and transportation were minor. The important role of the recycling potential also emerged. Unlike standard buildings, where heating-related impacts overshadow the rest of the life cycle, there is no single dominating item or aspect. Rather, several of them play equally important roles. The study has confirmed that the initial goal of environmental sustainability was reached, but to a much lower extent than previously thought. In comparison to a standard house, while the winter heat requirement was reduced by a ratio of 10:1, the life cycle energy was only reduced by 2.1:1 and the carbon footprint by 2.2:1.
Article
Le principal objectif de cette thèse a été de contribuer au développement d'un matériau de construction répondant aux nouvelles exigences des consommateurs et des législations en termes d'impact environnemental, d'impact sanitaire et de confort. Pour ce faire, une matrice pouzzolanique originale a été formulée et les adjuvants, renforts et granulats conventionnels ont été substitués par des matières premières renouvelables d'origine agricole. Les mécanismes de prise et de vieillissement du liant ainsi que les bénéfices de l'incorporation de deux adjuvants organiques sur ses propriétés à l'état frais et durci ont été décrits. Une étude comparative du renforcement mécanique de cette matrice par des fibres de lin, chanvre et yucca a ensuite été menée. Enfin, la compatibilité de ce liant avec des granulats végétaux (chènevotte du chanvre et moelle de tournesol) a été vérifiée, dans le but de formuler des composites permettant d'assurer une fonction d'isolation répartie.
Method for constructing a building using bricks connected using dry joints
  • D Baumer
D. Baumer, Method for constructing a building using bricks connected using dry joints, 2011.
Microbial growth after incubation in the different samples
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Fig. 12. Microbial growth after incubation in the different samples.
  • Météo France
Météo France, Bulletin climatique Rhône-Alpes, Avril, 2013a.
Bulletin climatique Rhône-Alpes, mai
  • Météo France
Météo France, Bulletin climatique Rhône-Alpes, mai, 2013b.