Épron, France
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Page J.,ESITC Caen | Sonebi M.,Queen's University of Belfast | Amziane S.,CNRS Pascal Institute
Construction and Building Materials | Year: 2016

An experimental investigation was conducted in order to study the properties of a hybrid hemp-flax composite material in term of capillary water absorption, mechanical strength, thermal conductivity and shrinkage. The hemp-flax composite material is made with 90% hemp shives and 10% flax fibers. Hemp aggregates have a high water absorption capacity, which led to a reduction of the hemp concrete mechanical performances. Four mixes were made for: shuttered walls, external coating, floor insulation and roof insulation. Firstly, bio-based aggregates were characterized in term of particle size distribution and water absorption. Then, the compressive strength of these four mixes was determined to compare the mechanical behavior of the hybrid composite material with hemp concrete. The capillary absorption and the total shrinkage of these bio-based materials were also measured. Finally, we measured the thermal conductivity coefficient of these materials. The results of the compressive strength show a significant improvement due to the incorporation of flax fibers. Flax fibers improve the compactness of the material, thus increasing its density, which leads to a greater mechanical strength. It was observed that the capillary absorption of hemp concrete seems to be related to the aggregates/paste ratio. Finally, flax fibers have reduced hempcrete shrinkage of about 15%. © 2016 Elsevier Ltd.


Page J.,ESITC Caen | Page J.,CNRS Crystallography and Material Science Laboratory | Khadraoui F.,ESITC Caen | Boutouil M.,ESITC Caen | Gomina M.,CNRS Crystallography and Material Science Laboratory
Construction and Building Materials | Year: 2017

An experimental investigation was undertaken on the physical characterization of a flax fiber-reinforced concrete (FFRC) in both fresh and hardened state. The objective of this study is to provide guidance for the mix-design of these FFRC. The study was conducted from two points of views: improving the workability of the concrete in a fresh state and improving the flexural strength in the hardened state. Several parameters have been studied independently as fiber length, fiber content, or the paste content. The characterization of flax fibers highlighted a high water absorption capacity which must be taken into account for the concrete mix-design. In addition, the flax fibers significantly impact the compactness of granular skeleton. For the characterization of concrete, testing in the fresh state showed a significant decrease of the workability of concrete with the addition of flax fibers. However, the use of shorter fibers, allows to reduce this damaging influence on the fresh concrete workability. Moreover, increasing the paste content allows compensating this fluidity loss. In the hardened state, the increase of the fiber content enhances the flexural strength, but a decrease of the compressive strength is observed. A greater porosity of the concrete was also observed with the incorporation of flax fibers. An increase in porosity was also observed when increasing the paste content. © 2017 Elsevier Ltd


Fabien A.,ESITC Caen | Fabien A.,CNRS Research Institute in Civil Engineering and Mechanics | Choinska M.,CNRS Research Institute in Civil Engineering and Mechanics | Bonnet S.,CNRS Research Institute in Civil Engineering and Mechanics | Khelidj A.,CNRS Research Institute in Civil Engineering and Mechanics
Key Engineering Materials | Year: 2017

Two approaches can be used to study the size effect: one based on the change in sample size, and the other based on the variation in the aggregates size. The main objective of this research was to study the second approach. We studied 6 various concrete mixes and each test was repeated three times. For each material, uniaxial cyclic compressive tests have been performed to investigate the behaviour of concrete in a partially damaged state. The specimens were submitted to three levels of loading corresponding to 30, 60 and 80% of the maximal compressive strength. The damage indicator chosen is the decrease of Young's modulus and the tightness indicator is the gas permeability. Results show that the concrete composition and more particularly the aggregate size have an important influence on the mechanical and transfer properties of concretes. © 2017 Trans Tech Publications, Switzerland.


Fouzia K.,ESITC Caen | Moussa K.,National Engineering School of Tarbes
Applied Mechanics and Materials | Year: 2011

Creep in cementitious materials is an important part of the delayed strains. It is a complex phenomenon in which many physical and chemical parameters are involved. In this paper, an experimental program was conducted to clarify the creep performance of CFRP strengthened mortar. The main parameters under study are the age at the time of loading and the drying. Specimens are tested at a sustained load of 30% of the ultimate strength. These investigations show the interest of the reinforcement by CFRP of the prismatic mortar specimens, this one allows a notable improvement of the creep behavior. ©(2011) Trans Tech Publications, Switzerland.


Sawsen C.,ESITC Caen | Fouzia K.,ESITC Caen | Mohamed B.,ESITC Caen | Moussa G.,CNRS Crystallography and Material Science Laboratory
Construction and Building Materials | Year: 2015

The association of plant fibers with cement paste raises a number of problems in both fresh and hardened states. Different treatments are applied to flax fibers with various methods within the aim to enhance the rheological properties of the cement mortar-fiber mixtures. Thus, the effects of these treatments on the properties of the fibers are evaluated. The rheological characteristics of the cement mixtures and the mechanical properties of the composites are assessed. Results show an improvement in the properties of the fibers, better rheological behavior of the cement mixtures and an increase of the mechanical strength of the composites. © 2015 Elsevier Ltd. All rights reserved.


Sawsen C.,ESITC Caen | Fouzia K.,ESITC Caen | Mohamed B.,ESITC Caen | Moussa G.,CNRS Crystallography and Material Science Laboratory
Construction and Building Materials | Year: 2014

Because of their hydrophilic nature, flax fibers absorb water during the mixing stage and release it gradually during the curing step. Thus, the rheological properties and the setting of the cement paste are deeply disturbed. In addition, the diametrical shrinkage of the fiber in the desorption stage can lead to a weakening of the fiber-matrix bond. It is therefore necessary to carry out treatment of the fiber and/or cement mixture to prevent the fiber/matrix debonding. The results obtained from these formulations show an improvement in the rheology and the mechanical performances of the composites. © 2014 Elsevier Ltd. All rights reserved.

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