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International audience; The fire reaction of various types of flammable lightweight materials is investigated using a cone calorimeter. The influences of parameters such as sample density, sample mass, effective heat of combustion and heat flux on the mass loss after exposition are discussed. Interpretations of the hemp fibers’ tests results lead us to propose a phenomenological model able to calculate the peak of heat release rate (pHRR) of such thermally thin materials, with or without flame retardant. A database gathering the whole results of tests performed on a large set of materials including fibers, bio-resources panels, bio-based concretes and fabrics is used to validate the proposed model. Interestingly, the model is found to be relevant also for denser wood specimens. The model is based on the distinction of the contributions of the exposed top layer and the deeper layer to the combustion. Indeed, in such materials, the heat conduction is limited (either by the intrinsic properties of the material or by the formation of an insulating char) and therefore the pHRR only depends on a limited volume of materials directly absorbing the heat flux from the radiant cone. Accuracy and limitations of the model are discussed.

International audience; L’utilisation de ressources végétales dans la formulation des matériaux permet de réduire l’impact environnemental du secteur de la construction. De telles ressources restent sensibles au feu. Cette étude vise à développer un traitement ignifugeant adapté aux isolants thermiques à base de fibres de chanvre. Le but est de limiter les impacts sanitaires et environnementaux du traitement, tout en optimisant les performances techniques des produits traités. Un protocole de laboratoire est mis en place pour évaluer l’effet retardateur de flamme du traitement. Les fibres traitées avec des solutions commerciales ou des formulations spécifiques sont soumises à différents essais de caractérisation incluant des essais d’inflammation directe, des essais à la petite flamme, des analyses thermiques (ATD-TG) et des essais au calorimètre à cône. Les résultats obtenus permettent d’orienter la formulation d’un traitement mais mettent également en évidence la complémentarité de ces méthodes d’analyse. Le couplage des résultats permet également de proposer un ajustement de modèles prédictifs conduisant à l’estimation du classement de réaction au feu selon l’Euroclasse des matériaux testés.

De nombreuses études portent sur les géopolymères, elles montrent qu’il est nécessaire d’adapter la formulation aux composants utilisés. Les différentes étapes permettant d’atteindre la géopolymérisation d’un alumino-silicate en milieu alcalin sont sensibles à toute modification des rapports molaires entre les atomes de Si, Al et M (cation). La présente étude est focalisée sur les Na-géopolymères. Plusieurs formulations sont testées et font l’objet d’un suivi massique et de retrait dimensionnel en jouant sur les conditions de conservation. Il apparaît des temps de stabilisation longs, de l’ordre du mois, et des retraits importants, de l’ordre de 10%. Le lien entre variation de volume et de masse évoque un retrait de séchage associé à la géopolymérisation. Par ailleurs, les résultats permettent d’estimer que près de 15% d’eau restait piégée dans la matrice après les différentes phases de géopolymérisation. Afin de réduire le retrait, l’introduction de charges de type silicate de calcium est testée. Elle conduit à la stabilisation dimensionnelle des échantillons durant le séchage., Academic Journal of Civil Engineering, Vol 37 No 1 (2019): Special Issue - RUGC 2019 Sophia Antipolis

Le béton de chanvre est composé de liant minéral et de fibres de chanvre. Les caractéristiques principales de tels bétons sont leurs propriétés hydrique et isolante très intéressantes. Cette étude entre dans le cadre du projet européen ISOBIO. L’un des enjeux est la contribution de la chaux dans les propriétés thermo-hydriques du béton de chanvre. Le présent article s’intéresse en particulier à la chaux commerciale Thermo®, BCB. Des mousses minérales ont été fabriquées à partir de ce liant minéral. Des densités comprises entre 500 kg/m3 et 1100 kg/m3 ont été atteintes. Après stabilisation massique, des essais de conductivité thermique et de Moister Buffer Value ont été réalisés. Les résultats obtenus sur la chaux sont très intéressants. Des conductivités thermiques comprises entre 0.11 et 0.25 W/(m.K) ont été obtenues, pour des valeurs de MBV respectivement de 2.5 à 1.9 g/(m².HR%). Les mousses de chaux fabriquées apparaissent comme de bons régulateurs hydriques, avec des valeurs de MBV semblables à celles du béton de chanvre. Les bulles d’air peuvent donc remplacer avantageusement les fibres de chanvre., Academic Journal of Civil Engineering, Vol 35 No 1 (2017): Special Issue - RUGC 2017 Nantes

Les objectifs de ce travail sont de développer et caractériser des éco-matériaux pour la réalisation de faux plafonds ou de cloisons. Les charges utilisées sont issues de papier recyclé (granules produits à partir de déchets de papier ou ouate de cellulose) ou de fibre de bois. Les liants choisis sont l’amidon, pour sa disponibilité et son faible coût en Côte d’Ivoire, et le plâtre, liant usuel en France qui servira pour comparaison. Cette étude examine premièrement la faisabilité de tels composés. La masse volumique des composites produits avec le plâtre s'étend de 400 à 1200 kg/m3, selon la formulation. Celle des composites granules de papier, réalisés avec l'amidon, est d’environ 500 kg/m3. La conductivité thermique, mesurée à la sonde fil à 23°C, 50%HR, augmente avec la masse volumique et se situe entre 0.09 et 0.5 W/(m.K). Les valeurs tampon hygriques, mesurée selon la méthode du Nordtest project, sont comprises entre 0.61 et 2.85 g/(m².%HR) selon les formulations testées, incluant plus ou moins de charge et plus ou moins d’eau., Academic Journal of Civil Engineering, Vol 34 No 1 (2016): Special Issue - RUGC 2016 Liège

Le projet européen ISOBIO cherche à développer de nouveaux matériaux isolants biosourcés de manière à réduire l’impact environnemental des constructions. L’énergie grise de ces matériaux doit être faible de même que leur bilan carbone. Ils doivent également réduire les besoins énergétiques des bâtiments tout en assurant un bon niveau de confort thermique et hydrique pour les usagers. Cette étude s’intéresse à la valorisation des agro-ressources en tant que granulats et en tant que liant afin de produire des composites intégralement biosourcés. Les composites développés sont réalisés à base de chènevottes liées avec de la paille de blé. Après une étude de faisabilité qui considère plusieurs protocoles d’utilisation de la paille de blé comme liant et plusieurs ratios chanvre/paille, trois composites sont sélectionnés. Des échantillons sont fabriqués pour déterminer leurs performances hygrothermiques. Les propriétés mesurées sont intéressantes : leur conductivité thermique est faible (0.071 à 0.076 W/(m.K)) et les matériaux s’avèrent être d’excellents régulateurs hygriques (MBV > 2 W/(m².%RH))., Academic Journal of Civil Engineering, Vol 34 No 1 (2016): Special Issue - RUGC 2016 Liège

The classic models describing the hygric mass transfers inside building materials seem unsuitable in the case of bio-based materials. They are based on the assumption of an instantaneous local equilibrium between relative humidity and water content evolving according to the diffusive fluxes and the sorption isotherms and predict much shorter times of stabilization than those obtained experimentally. A new approach is presented here, it frees from the local instantaneous equilibrium introducing a local kinetics to describe the transformation of water from vapor state to absorbed liquid state and vice versa. In the framework of the European ISOBIO project, a multilayered wall mainly made of bio-based materials has been developed. The different layers have been characterized in terms of sorption, vapor permeabilities and thermal conductivities. The sorption measurements performed on representative samples have allowed to determine the local kinetics constants. Then, the hygrothermal behavior of the test wall has been studied thanks to an instrumented demonstrator (HIVE demonstrator, Wroughton, UK). The recorded measurements are compared to simulations based on the instantaneous local equilibrium model (TMC code) and on the local kinetics of sorption model (TMCKIN code). It appears that TMC very significantly underestimates the dynamics of the local relative humidities variations whereas TMCKIN succeed in predicting this dynamics and leads to results close to measurements., Academic Journal of Civil Engineering, Vol 37 No 2 (2019): Special Issue - ICBBM 2019

The European ISOBIO project allowed to both develop new bio-based building insulation materials and improve industrial products from the partners of the project. It leaded to several multi-layers solutions to be used as typical wall for new building or for retrofitting. The hygrothermal behavior of these walls is studied experimentally (two demonstrator buildings and one laboratory test-wall) and numerically. This study investigates the hygric characterization of the materials used to produce the core of the new wall solution: compressed straw board (CSB), commercial oriented strand boards (OSB), soft insulation panels (Biofib trio, CAVAC), rigid insulation panels developed within ISOBIO project (CAVAC panel). This paper presents the methods and the results obtained on absolute and apparent densities, total porosity, sorption isotherm, water vapor permeability at dry point and at wet point, and moisture buffer value. The studied materials are highly to very highly porous (60 to 98 %). They are hygroscopic. Their water vapor resistance factor is low for Biofib insulation, high for OSB and medium for CSB and CAVAC panels. It decreases between dry point and wet point in link with the hygroscopicity of materials. Their MBV gives them moderate to good moisture buffering ability (respectively for CSB and OSB, and for Biofib and CAVAC panel). The study provides an entire set of results that widely characterize the hygric behavior of studied materials and allow to compare them. It underlines very different behaviors, particularly under transient conditions. These data are useful to be implemented in numerical models that simulate hygrothermal behavior at wall scale., Academic Journal of Civil Engineering, Vol 37 No 2 (2019): Special Issue - ICBBM 2019

In the frame of Isobio project, several multi-layers solutions were developed to be used as typical wall for new building. The proposed solution wall is made of a wood frame and a commercial oriented strand board (OSB) filled with flexible insulation panel (hemp-flax-cotton panel). Rigid insulation panels placed on each faces (compressed straw board and rigid hemp panel) support a lime based external render and a clay-based plaster. Alternatives solutions are derived from the referent solution. The fire resistance of three building solutions is evaluated at a representative scale using ISO 834 fire curve. Four test configurations are tested placing thermocouples at each interface of the multilayer wall to record the heating kinetic. Smoke resistance, cracks and color changes are quoted during the test. The analysis of specimens degradation during fire test is full of interest to understand the fire behavior of such type of bio-based materials and to confirm the design of the proposed building solutions. It is confirmed that the plaster or the render layers have a key role in the fire behavior. The results obtained with the referent solution highlight the relevance of the solutions., Academic Journal of Civil Engineering, Vol 37 No 2 (2019): Special Issue - ICBBM 2019

This study deals with the development of novel fire-retardant formulations to reduce the flammability of a low density rigid insulation panel made from hemp shiv glued with a thermosetting bio-binder. The objective is to identify possible substitutes to conventional fire-retardants, which are free from ammonium salts or boron compounds. The effect of the different treatments on the thermal decomposition of hemp shiv was analyzed by TGA/DA. The fire reaction of the insulation panel made of treated hemp shiv and bio-binder was characterized using the standardized cone calorimeter test. Two conventional treatments are used as references: a commercial ammonium phosphate/sulfate flame-retardant and a commonly used flame-retardant composition based on boric acid. Results showed that magnesium sulfate heptahydrate, phosphoric acid, sulfuric acid, functionalized silica particles and a combination of these could provide better fire retardancy effect than the conventional treatment based on boric acid. However, some treatments were not compatible with the selected panel formulation because they hindered the thermosetting binder polymerization leading to poor mechanical properties., Academic Journal of Civil Engineering, Vol 37 No 2 (2019): Special Issue - ICBBM 2019

The European ISOBIO project aims to develop new bio-based insulation panels and coatings showing low embodied energy and high hygrothermal efficiency. After optimization of composites, typical walls for new building and retrofitting will be designed, targeting energy saving and indoor comfort. These multi-layers walls will include indoor plaster that will highly contribute to indoor comfort. This paper investigates the moisture buffering capacity of clay-based plasters. Three formulations developed within the ISOBIO Project, are investigated. These formulations are clay-based and include hemp powder and pumice. After weight stability, drying shrinkage is measured and thermal properties are evaluated for densities ranging from about 1250 to 1425 kg/m3. Thermal conductivities are closed to values commonly measured on earthen materials. The measurement of Moisture Buffer Value (MBV) is performed following two type of protocols. After stabilization, specimens are exposed to daily cyclic variation of ambient relative humidity. For each formulation, three thicknesses of specimens are considered. The lower thickness, about 1.3 centimeters, is representative of the plaster in-use. So, the MBV is representative of in-use behavior. The two higher thicknesses are used with the aim to study the effect of thickness on MBV and to identify MBV representative of the material’s one. Consequences of protocol modification in MBV measurement is evaluated and discussed. The three tested plasters are classified as good hygric regulators. A slight discrepancy appears between the three formulations (about 6.5 % for the in-use thickness) showing the limited incidence of formulation changes., Academic Journal of Civil Engineering, Vol 37 No 2 (2019): Special Issue - ICBBM 2019

La durabilité d’un coulis géothermique est évaluée dans les conditions d’usage d’une sonde géothermique verticale. L’étude intègre une approche expérimentale et des modélisations géochimiques. Le vieillissement accéléré du coulis géothermique est évalué en laboratoire en reproduisant le type d’agressions géochimiques et thermiques auxquelles le coulis peut être soumis. Les paramètres liés à la conductivité thermique et la perméabilité sont particulièrement suivis. Un montage expérimental permet de reproduire les conditions d’exploitation d’une sonde géothermique dans des conditions de confinement réalistes. Les résultats expérimentaux alimentent des modèles de dégradation géochimique permettant de simuler sur une échelle de temps longue la dégradation autour de la sonde. Des conclusions portant sur la durée de service découlent de cette étude., Academic Journal of Civil Engineering, Vol 36 No 1 (2018): Special Issue - RUGC 2018 St Etienne

The need to reduce greenhouse gases emission produced by the building sector leads to the research of renewable and less impacting materials that can replace traditional ones. This study focuses on development of a new sustainable building material using hemp and natural clay. In this work, experimental investigation was carried out to study the mechanical performance of hemp clay composite. The composites are made with different Hemp to Binder mass ratio. The hemp to Binder ratio is estimated regarding traditional mix proportioning of hemp concrete used for floor, wall and roof. Firstly, hemp shiv was characterized in term of density, particle size distribution and water absorption. Then, the mechanical properties are determined to compare the mechanical behavior of the hemp clay composites with hemp concrete. The results show that the density of the composite materials varies with the H/B ratio. The density range between 373 kg/m3 and 510 kg/m3. It is shown that mechanical properties depend strongly on the Hemp to Binder ratio and on density. The tensile strength ranges from 0.021 to 0.026 MPa and the compressive strength ranges from 0.39 to 0.48 MPa. The results show that the mechanical performance of produced composite materials meets the requirements of the intended use., Academic Journal of Civil Engineering, Vol 35 No 2 (2017): Special Issue - ICBBM 2017

ISOBIO Project aims to produce highly insulating panels from bio-resources. This study focuses on the constrains associated to the production of panel at the industrial scale using thermal treatment. Three types of processes are considered (wet processes for rigid panels, dry processes for rigid or flexible panels and Stramit process®) and the limits of each process are identified according to the formulation characteristics (moisture content, binder type and content), binding mechanisms (melting, thermosetting or drying), process parameters (pressure, time and temperature) and targeted material properties (density and thickness). Cavac Biomatériaux industrial oven is used to study the dry and wet processes for the production of rigid panels. The temperature distribution in the material thickness was recorded. Difficulties to reach sufficient temperature level for high panel thicknesses or for high water content are observed. As a consequence, an excessively long drying time is needed to produce rigid panel using the wet process. Only small panel thicknesses are possible options. The addition of thermosetting binder is an alternative way to reduce water content and processing time. Rigid panel are easily produced using the dry manufacturing process and a hydraulic press with hot plates. Various tests are performed adjusting panel characteristics and formulations. Interesting results are obtained with hemp shiv bonded with a bio-based thermosetting binder. The binder content ranged from 5% to 23% and the targeted density from 155 to 245 kg/m3. Mechanical characterization shows that the binder formulation, proportion, water content and panel density are crucial parameters to be adjusted to optimize panel manufacturing process and properties. The dry process appears more versatile than wet process and leads to lower processing time. It allows the production of hemp shiv insulation panels within a large range of density and having compressive and flexural strength reaching 1 and 1.7 MPa respectively., Academic Journal of Civil Engineering, Vol 35 No 2 (2017): Special Issue - ICBBM 2017

The ISOBIO project proposes an innovative strategy to bring bio-based construction materials into the mainstream. A key innovation consists of the use of bio-based aggregates from a local culture, with green binders for the production of ecofriendly composites. This work aims to combine existing technologies in order to develop bio-based panels with high insulating properties, low embodied energy, low embodied carbon and hydrothermally efficient. This study aims to value the agro-resources by-products from flax, hemp, corn, rape and wheat, provided by one of the project partner, for find out new alternative materials that respond to sustainable development criteria. In the present work, the chemical characterization of agro-resources’s byproduct are studied by Van soest method and Phenol sulfuric method to determine the content of cellulose, hemicellulose, lignin and polysaccharides. Measurement of thermal conductivity and Moisture Buffer Value are also achieved in these raw materials to determine their hygrothermal properties at bulk density. Thermal Conductivity and MBV evolve according to the density whatever the agro- resources type. All these materials have different properties but they are all excellent hygric regulators. These results suggest that agro-resources’s by-product may be used as a raw building material but not for the same types of use. In fact, some raw materials would be more suitable for thermal insulating products and others would be better suited to indoor facing panels., Academic Journal of Civil Engineering, Vol 35 No 2 (2017): Special Issue - ICBBM 2017

The European ISOBIO project aims to develop new bio-based building insulating materials which contribute to reduce environmental impacts of buildings. The developed materials shall have low embodied energy and low carbon footprint and shall contribute to reduce energy needs of buildings ant to ensure high hygrothermal comfort of users. This study investigates the valuation of agro-resources as bio-based aggregates and as binding material to produce wholly bio-based composites. Two types of aggregates: hemp shiv and corn cob residues (obtained after alkali treatment on the corn cob), and five types of green binders are investigated. Specimens are produced to characterize thermal and hygric properties of developed composites and to identify the best mixture between aggregate and binder. They show interesting thermal and hygric properties. They have low thermal conductivity ranging from 0.067 to 0.148 W/(m.K) and depending on the mix (aggregate with binder). They are excellent hygric regulators (MBV >2 g/(m².%RH)). These results suggest that developed composites can be used as building materials but not for the same types of use. In fact, some composites would be more suitable for thermal insulating products and others would be better suited to indoor facing panels., Academic Journal of Civil Engineering, Vol 35 No 2 (2017): Special Issue - ICBBM 2017

This study aims to design cheap and environmentally friendly materials well suited for ceiling or interior walls of buildings. This project focuses on valorization of raw materials available in Ivory Coast. Developed composites are realized with eco-materials issued from local recycled or biobased materials: recycled paper (granules or cellulose wadding) and wood fiber. Aggregates or fibers are bonded with starch. This study investigates several water to starch ratio for each kind of load and two loads to binder ratio are also considered for paper granules. After production, hygric and thermal characterization of the composites is performed. At dry state, the densities of produced composites range from 300 to 600 kg/m3 and thermal conductivities range from 0.09 to 0.17 W/m/K. Moisture buffer values of the composites are measured as defined in the Nordtest protocol. All composites are at least good hygric regulators according the Nordtest project classification. When the paper granule content increases, the composites reach excellent hygric regulator levels whereas their thermal conductivities increase., Academic Journal of Civil Engineering, Vol 35 No 2 (2017): Special Issue - ICBBM 2017

Hemp lime concrete is a mix of hemp shiv glued in a mineral binder. Such concrete is characterized by low thermal conductivity and interesting hygric properties. The aims of this study realized in the frame of ISOBIO Project is to understand which is the contribution of each component of the hemp lime concrete to the thermo-hygric properties of the mix. The study focuses on the case of a commercial hemp shiv (Biofibat®, CAVAC France) and a lime based binder (ThermO®, BCB). The measurement of thermal conductivity and Moisture Buffer Value are performed on some conventional hemp lime concrete formulations. On the other hand, the same measurements are performed on hemp shiv alone (at different density) for several grading showing that thermal Conductivity and MBV evolves according to the density. The last measurements are realized on samples realized with ThermO® lime matrix foamed to achieve sufficiently low densities ranging from 500 kg/m3 to 1100 kg/m3. The comparison of results obtained on each component and on mixes for the same range of density is full of interest to evaluate occurrence of a synergetic effect, or not. The data are used to adjust a model useful for the optimization of the mix proportioning., Academic Journal of Civil Engineering, Vol 35 No 2 (2017): Special Issue - ICBBM 2017

International audience; The objective of the present study is to show how recording the changes in the rotation torque according to the rotation speed can lead to identifying a characteristic flow curve for the tested concrete. The concrete rheometer used for the study is composed of a vane tool. The rotation speed of the tool is imposed and the resulting torques are measured. The experimental rotation protocol used in this study corresponds to a rapid speed increase followed by a steady speed then the rotation speed slows down. The evolution of the torque measured as the rotation speed decrease (restructuring phase) is considered as being a succession of stationary states. By considering the fluid equivalent to a Bingham fluid for which the yield stress has already been identified and by using an analogy with a coaxial-cylinders rheometer, relevant relationships between the rotation speed of the vane and the rate of shearing along the tool are identified. Shear stress and shear rate calculations for each value of torque and rotation speed lead to the complete flow curve of the tested fluid. The data treatment method is adjusted to accurately evaluate the parameter linked to the flow stop in the case of a non-nil shear rate when the yield stress is reached. The comparison of the characteristic rheological parameters of SCC obtained from the rheometer and both spreading and V-Funnel tests indicate very satisfactory correlations.

International audience; The efficiency of thin mineral passive fire protection layer applied on concrete is analyzed. The more suitable fireproofing material formulations are selected from results of laboratory scale fire test. Such tests consist in the direct exposure of protected concrete samples to the flame of a burner, at constant temperature (850°C). Various formulations of mineral fireproofing materials have been tested to identify the effects of binder type and the density. Formulation compromises are highlighted regarding requested fire performances. Selected formulations are used to protect real scale concrete slab exposed to standard fire (ISO 834). During the test, the concrete/fire protection layer interface temperature and the steel reinforcement temperature have been recorded. For small size slabs, fire proofing layer is completely efficient. The temperature increases are strongly delayed. For large size slabs, delamination of fire proofing layer appears, leading to rapid concrete degradation. To understand the mechanics of cracking and delamination of fire protection layer, laboratory scale tests are performed with two selected formulations varying the implementation methods (surface treatment of concrete, intervention on interface roughness, precracking). It appears that the occurrence of fire protection layer delamination can be avoided choosing the optimal implementation method without adjustment of the optimized formulations. From the 8th International Conference on Concrete under Severe Conditions - Environment and Loading, CONSEC 2016