Thibaut Lecompte

Université Bretagne Sud | UBS · IRDL – Institut de Recherche Dupuy de Lôme

La terre allégée est un mélange de terre et d'agrégats végétaux (comme la chènevotte), dont la conductivité thermique est inférieure à celle de la terre crue (80 mW/m.K) et pour lequel l'impact environnemental est moindre que celui des mélanges chaux/chanvre. Ce matériau est utilisé actuellement pour de la rénovation de bâti ancien ou les construct...

Insulating building envelope is an efficient way to increase building energy efficiency and minimize greenhouse gas emissions related to heating. After building refurbishment, on-site measurements are suitable for verifying the actual thermal transmission properties of plane building components. For instance, the standard ISO 9869-1 describes a HFM...

Light earth is a natural insulating material composed of earth and vegetal fibres. It can be used to insulate existing and new buildings to reduce energy and resources consumption, and excavated earth generation by the construction sector. A pedological database is crossed with suitability thresholds in order to evaluate spatially the availability...

Dans le cadre de la lutte contre le dérèglement climatique, les matériaux à base de chanvre ont un rôle à jouer, grâce d’une part à leurs propriétés physiques singulières, et d’autre part car ces matériaux stockent du carbone : les matières végétales captent le dioxyde de carbone de l’atmosphère lors de la photosynthèse, et gardent une part de carb...

Il est nécessaire d'optimiser la mesure de la conductivité thermique pour améliorer l'estimation de la consommation énergétique des bâtiments. L'effet de la migration de l'humidité sur la mesure de la conductivité thermique des matériaux humides est examiné au cours d'un test HFM. Tout au long de l'essai, l'humidité se déplace du côté chaud au côté...

Du fait de leur contenu carbone, les matériaux biosourcés pour le bâtiment sont a priori de bons candidats pour lutter contre le réchauffement climatique. Cet article propose un bilan des enjeux autour de la substitution des matériaux conventionnels par des matériaux biosourcés. Pour juger du potentiel réel d'atténuation du réchauffement climatique...

The common reed, Phragmites australis, is a plant species quite similar to the currently used bio-based aggregates and available on most continents. The purpose of this work is to characterise this common reed and compare its properties to other plants already studied for building use. This study presents the different properties focussing on Phrag...

The global challenge of large-scale climate change mitigation requires action also in the building and construction sector. From a life cycle perspective, and considering the mitigation timeframe, the issue of reducing embodied GHG emissions is gaining attention. Effective ways to reduce embodied GHG emissions have been proposed by the use of fast-...

The global challenge of large-scale climate change mitigation requires action also in the building and construction sector. From a life cycle perspective, and considering the mitigation timeframe, the issue of reducing embodied GHG emissions is gaining attention. Effective ways to reduce embodied GHG emissions have been proposed by the use of fast-...

Thermal conductivity is of high importance for insulating materials since it strongly influences the thermal performance of the building. Generally, it is recommended to measure this property with steady-state methods like guarded hot plate (GHP) or heat flow meter (HFM). These methods are reliable, but steady-state condition can take a long time t...

This paper concerns the packing of plant particles (hemp shiv) used for building applications and aims to quantify skeletal, particle and packing densities and associated porosities. These parameters were measured on hemp particles as a case study and were used to assess the physical behaviour of this material in terms of water adsorption and absor...

The Hot Disk transient plane source (TPS) method allows characterizing the thermal properties of various materials in a few minutes. Particularly, it is increasingly used for evaluating thermal conductivity of insulation building materials. However, the results of such measurement frequently differ from steady state measurements because of the sign...

During cement hydration, solid, fluid, and total volumes vary as water is consumed by chemical reactions. Those volume variations lead to pore water pressure decrease during the first hours of hydration. The deformations induced by early hydration are quantified in order to understand their consequences on the internal stress state within the harde...

In a slipforming process, concrete is continuously poured and the formwork simultaneously raised so that the older concrete on the bottom supports the fresher on the top after a few hours of hydration. The objective of the present study is to examine the evolution of the concrete/formwork interface at very early age. An experimental device was desi...

This study focuses on the compression behavior of hemp shiv layers for bio-based floating floor applications. An experimental campaign was performed to measure the instantaneous and creep behavior of different hemp shiv. The effect of humidity was also taken into account. A model was developed to assess both instantaneous and creep behavior of the...

In a static Life Cycle Assessment (LCA), the global warming potential (GWP) is calculated assuming Green House Gas (GHG) impact to be independent of their emission or uptake timing.This study investigates if this approach is adequate to fully capture the global warming impact (GWI) of building materials. Static LCA (sLCA) was compared to dynamic LC...

Composites based on lignocellulosic fillers such as wood, miscanthus or common reed have received much attention due to their low cost and positive impact. Knowledge of the physico-chemical characteristics of plant flour is essential to obtain indications of the thermal stability and humidity behaviour of the resulting biocomposite. The different m...

This experimental study provides complete datasets of hygrothermal properties of numerous hemp-clay with density ranging from 200 to 350 kg m⁻³ for building thermal insulation. In addition, attention is also paid on protocols and methods, on the measurements repeatability and on the influence of conditioning temperature and relative humidity: mean...

For concrete and other cement-based materials, cement hydration induces Le Chatelier contraction. This phenomenon creates negative pore water pressure, which increases the bulk and interfacial granular stresses and affects both the interfacial and bulk rheological behavior of the dense mineral suspension. An original device was developed to assess...

h i g h l i g h t s Cohesive behaviors of 6 earth are studied through yield stress measurement. The study is based on samples representative of Brittany and Normandy earth natural variability. Existing or new rheological tests are compared to evaluate their accuracy and validity range. Results allow to control an earth slip yield stress knowing its...

(https://www.techniques-ingenieur.fr/) Dans le contexte actuel de recherche de solutions pérennes de lutte contre le réchauffement climatique induit par les gaz à effet de serre (GES), le milieu de la construction a un rôle à jouer. L’utilisation de matériaux bio-sourcés dans les bâtiments neufs et en rénovation apparaît comme une piste crédible d...

Hygrothermal simulation of bio-based materials requires heat or moisture storage and transfer properties. Even if their determination is defined in numerous standards, characterization implies uncertainties. In this work, we aim to evaluate the uncertainties in the determination of heat and moisture storage properties of light earth insulation mate...

Wood-plastic composites (WPCs) are water-sensitive materials. Standards describe water absorption protocols on composites to obtain results after a long period of aging. From an industrial point of view, it is necessary to obtain the same information (i.e. equilibrium water content and absorption kinetics) over a short time. In this paper, we propo...

The present study aims to evaluate the impacts of raw material variability (earth and hemp) on hemp–earth performances. This work is performed in the framework of the ECO-TERRA R&D project in collaboration with four French research laboratories, short circuit hemp producers and craftsmen specialized in hemp and earth constructions. This article is...

In the present experimental work, 28 reinforced concrete beams were manufactured and tested in bending under 2 concentrated loads. The beams, which were made in high strength concrete and in ordinary concrete for comparison purposes, had different quantities of fibres, with two aspect ratios. During the testing, a special attention was given to the...

Due to aerodynamic instabilities induced by combination of rain and wind, civil engineering cables are submitted to cyclic loadings during their whole operating life. To prevent them from fatigue issues, internal and external dampers are increasingly used. Recently, innovative damping devices based on Shape Memory Alloys have demonstrated a true ef...

Due to its low environmental impact, earth construction has received lot of consideration in recent years. Furthermore, in order to improve the quality of earth construction, there is a need for a better description and control of the earth consistency or rheology. Just as for concrete with the Abrams cone, there is need for a simple and robust tes...

Necessité de la prise en compte du temps de stockage temporaire de carbone pour distinguer les apports des matériaux biosourcés en termes de limitation du dérèglement climatique: importance de la pratique cultural, des transports, de la fin de vie et du temps de stockage (durée de vie du produit et des bâtiments)

Four-points bending tests were carried out on high performances concrete beams without stirrups and with stirrups, designed to consider shear behavior, and using digital image correlation technique (DIC). In the experimental device, the shear zone between the support and the loading point was digitized by high resolution camera. The numerical analy...

The present study aims to evaluate the impacts of raw materials variability (earth and hemp) on hemp-earth performances. This work is performed in the framework of the ECO-TERRA R&D project in collaboration with four French research laboratories, short circuit hemp producers and craftsmen specialized in hemp and earth constructions. This article is...

The present study aims to evaluate the impacts of raw materials variability (earth and hemp) on hemp-earth performances. This work is performed in the framework of the ECO-TERRA R&D project in collaboration with four French research laboratories, short circuit hemp producers and craftsmen specialized in hemp and earth constructions. This article is...

It is commonly considered that the yield stress of SCC increases linearly at rest. This increase is due to the SCC structural build-up. This behavior can be explained by the cement particle nucleation at the contact points. During the first dozens of minutes, the cement particle nucleation induces a linear increase of the yield stress in time. Howe...

The well-known martensitic transformation is not always the unique solid-solid phase change in NiTi shape memory alloys (SMA). For this material, R-phase can occur from both austenite and martensite. In some applications, macroscopic strain of the material can be limited to 2%. In these cases, R-phase contribution can not be neglected anymore when...

Straw bales are seen as increasingly viable for building insulation and even for the construction of small load-bearing straw houses in the last decades, especially in view of the need to seek low environmental footprints. Straw bales can be used as load-bearing structures but they are currently mainly used as a filler insulation material associate...

This paper deals with the mechanical behaviour of lime hemp composites. LHC blocks have been produced by compression in a rigid die at a relatively high compression pressure. This process allows the production of LHC with a high proportion of hemp shiv. New mechanical parameters are proposed to compare experimental results of this study with those...

Shear failure of reinforced concrete beams is generally affected by a large number of parameters among which the a/d ratio (shear-span/effective depth) is the most important. The other main parameters are the compressive strength, the longitudinal reinforcement ratio, the aggregate and the presence of transverse stirrups. The addition of steel fibe...

This paper deals with the use of plant fibres, such as coconut, as reinforcement in cementitious materials; such additions modify the mechanical properties of the composite in its hardened state. This enhancement depends on both the fibre’s physical and chemical properties. For reinforcement of the mineral matrix, the interfacial properties are par...

This study deals with the inclusion of micro encapsulated phase change materials (PCM), up to 29% in volume, in concretes and mortars. Thermal and mechanical characteristics of hardened mixes are measured and compared with classical civil engineering models. PCM microcapsules behave as voids on a mechanical point of view, and as properly dispersed...

Cement-based materials typically exhibit low tensile strength and their behaviour is generally brittle. Fibres can be added to make composites with enhanced tensile response and toughness. This study focuses on the effects of flax fibre content, mix design and processing on the hardened product properties (density, fibre orientation, surface qualit...

This paper deals with the processing of lime hemp composite blocks by compaction. A rigid compression die has been developed to reach relatively high compression pressure. This has been fitted with force and strain transducers to measure the stress state during compaction. It provides some means of understanding the effect of mix design and stress...

Low rise buildings and rural houses in Indonesia are often constructed with non-standard bricks. In some provinces, like West Java, fired clay and unfired soil lime bricks co-exist as non standard bricks. These bricks are traditionally produced in home run plants with little adherance to appropriate mix designs. These unfired soil lime bricks enter...

For perfect and homogeneous plastic materials, the extrusion stress and flow typology have previously been well described. However for firm pastes, during extrusion, liquid phase migration may appear leading to unsuccessful processing. Reviewed literature explains that there is a competition between the extrusion velocity and the liquid filtration...

The structural build-up of rigid fiber reinforced cement-based materials is studied. It has recently been shown that the behaviour of fiber reinforced concrete depends on the orientation of the fibers that has to be optimized during casting. As a result, there is a great interest to study the rheology of fiber reinforced concrete. One of the most i...

The coconut fiber presents higher ductile properties than other natural fibers. In previous studies, it demonstrated than Indonesian coconut fibers presents an improved tensile strength and failure strain after washed with water and dried. The coconut fibers have the potential to reinforce material for construction, especially in earthquake areas s...

In this work, ternary mixes of sand, cement and kaolin are studied in order to design extruded building products with reduced environmental impact. Firstly, the amount of water required to reach the extrusion rheological criterion and the immersed mechanical strength are studied. Results lead to a compressive strength prediction tool (derived from...

Les structures à câbles de génie civil sont soumises à de sévères sollicitations mécaniques dans un environnement extérieur agressif. En particulier, la fatigue et le fretting-fatigue sont dus à des phénomènes d’instabilités aérodynamiques, provoquant la mise en vibration transversale des câbles. Pour allonger la durée de vie des câbles, il est don...

Most of civil engineering cable structures are subjected to potential damages mainly due to dynamic oscillations induced by wind, rain or traffic. If vibration amplitudes of bridge cables for example are too high, it may cause a fatigue phenomenon. Recently, researches had been conducted dealing with the use of damping devices in order to reduce vi...

Natural fibers such as coconut fibers are numerous in Indonesia. The tensile strength of coconut fibers produced in this country is among the highest of natural fibers ones. This paper is to determine the tensile strength of coconut fibers with or without special treatment (water washing dry) and assessment the ability of coconut fiber for reinforc...

We focus in this paper on a potential correlation between yield stress and bleeding. We suggest that the conditions under which a fresh cement paste is able to display a yield stress result from the competition between Brownian motion and colloidal interactions whereas the conditions under which the suspension is stable result from the competition...

Dans cette étude, nous présentons l'évaluation des performances de plusieurs mélanges ternaires de ciment, de sable et de kaolin. Le but est de valoriser par extrusion et stabilisation au ciment des matériaux locaux et de fournir des informations sur leurs caractéristiques mécaniques et leurs stabilités dimensionnelles. La quantité d'eau permettant...

This study presents original results on the rheological measurement of concrete mixes. It focuses on how to determine their mechanical and physical behavior under shearing stress. More specifically, the in fluence of aggregate content on shearing properties is studied. A vane rheometer was developed to characterize fresh cement-based materials. In...

Mechanical characteristics (i.e., stiffness, internal friction angle, peak strength) and crushability of a soft granular material were evaluated by performing a comprehensive series of laboratory tests using the following devices: standard and non-standard triaxial apparatus, direct and annular shear box, oedometer and hydrostatic devices. The init...

Fresh cement paste permeability is a key parameter to understand the hydro-mechanical behavior of cementbased materials, i.e., rhelogical properties and static stability. However, its permeability measurement is not easy to assess. The porous medium is not rigid and tends to change due to hydration kinetics. Two measurement methods, with 70 mm and...

Société Française de Thermique, 24-27 Mai 2011 Perpignan.

Some preliminary studies, dealing with the process optimisation of pre-cast building elements made of Lime and Hemp Concrete (LHC), have shown that compression during casting lead to significant improvements: better mechanical characteristics and facing. However, this compaction leads to an increase of the weight to volume ratio and to a decrease i...

Some preliminary studies, dealing with the process optimisation of pre-cast building elements made of Lime and Hemp Concrete (LHC), have shown that compression during casting lead to significant improvements: better mechanical characteristics and facing. However, this compaction leads to an increase of the weight to volume ratio and to a decrease i...

A new device, consisting of a rough plate immersed in the fluid sample, was developed to enable a simpler measurement of the sedimentation and yield stress increase of non-Newtonian suspensions. Due to the deformation of the material at rest or due to changes in the solid volume concentration by sedimentation along the vertical axis, the plate appa...

A method is presented to measure elastic parameters of green powders compacted into a die. It requires an instrumented rig fitted with force transducers on the two punches and a die allowing the measure of radial stresses. Following compaction, the unloading phase is analysed assuming for the powder an isotropic linear elasticity. The equations of...

La granulation sèche de poudres organiques pose des problèmes : parfois il faut une mise au point très longue avant d'obtenir les paramètres optimaux de compaction ; d'autres fois on n'y parvient pas. Bien connaître l'aptitude à la compaction et à la granulation des poudres reste ainsi un enjeu très important pour les industriels qui utilisent ou p...

Nowadays dry granulation of powders has become a very important research topic because it is the most economic way of granulation, making the particle handling easier, and avoiding the loss of material during particle processing, or particle transfers. This kind of process has been deeply studied but a better knowledge appears necessary to control...