Résumé: This study investigates the performances of a new material composed of cement binder and natural vegetal diss fibers. The main goal is to use a locally abundant plant (diss) as a substitute for aggregates, in order to produce a lightweight material with excellent thermal insulation. Three composites with diss fiber content of 20%, 25% and 30% by weight of cement were produced, and their thermal and mechanical performances were experimentally investigated. At first, the flexural strength, toughness index, compressive strength and toughness energy of the composites were examined. Then, thermal properties in terms of conductivity, diffusivity and effusivity were evaluated for the three composites. The results show that incorporating a large amount of diss fibers in the cement matrix causes an increase in the porosity of the composite and consequently a reduction in density. The high porosity of the composites causes a significant reduction in compressive strength. However, the toughness of the composites in the post-cracking stage is significantly enhanced. Under three-point loading, the diss-fiber-reinforced composites exhibit pseudo-ductile post-peak behavior with high values of toughness index (I5). The low density is accompanied by an improvement in the composites’ thermal performance, with a significant decrease in thermal conductivity, thermal diffusivity and thermal effusivity. According to RILEM, the developed composites could be classified as lightweight insulating materials and can be used in non-load bearing walls and insulating fillers.

Résumé: The viability of using vegetable Ampelodesmos Mauritanicus (Diss) fibers to develop lightweight construction material was investigated in this paper. The objective of this work is to assess the physico-mechanical properties of Diss fibers reinforced concrete sample with fibers to binder volume ratio ranged from 0 (control specimen) to 4. In order to mitigate the inhibitory effect exerted by vegetable materials on binder hydration, Diss fibers were treated with hot water, while air lime-based binder has been selected to replace traditionally used cementitious binder. The most important part of this work is focused on the efficiency of using air lime-based binder to develop lightweight construction material containing Diss fibers. Air lime-based binder is the chosen variety of binder due to its abundance and low emissions from its manufacture. The experimental investigation of the chemical compatibility between treated fibers and binder through the hydration-test has shown the effectiveness of boiling water treatment on the modifications of morphological and mineralogical properties to overcome the inhibitory effect exerted when non-treated Diss fibers were used. The hardened specimen properties included dry density, porosity, compressive and flexural strengths, and elastic behavior have been studied. The results have indicated that despite a reduction in compressive strength, the reinforced specimen remains acceptable to be used in lightweight construction applications, as regards its compressive strength-value and lightening level. The flexural strength of reinforced specimen was found to be significantly enhanced. Depending on the amount of Diss fibers used in the mixture, it was found that the optimal addition of Diss fibers is in the range of 3 volumes content. The corresponding flexural strengthening rate has reached a value of 86.5 % higher, due to the several reinforcement mechanisms like the compaction process, Diss fiber bond reinforcement, and also the undisturbed development of hydrate components of air lime-based binder during hardening. Therefore, the addition of Diss fibers generates failure mode change of specimen from the brittle to ductile behavior, which results in improvement of deflection and toughness capacity.

Résumé: Concerned about the environmental and economic impact, composite materials are increasingly used in the construction sector. Indeed, the use of plant fibers as reinforcement in construction materials have been the subject of several researches in recent years; the main motivation is the weight gain combined with high mechanical characteristics. The objective of this research concerns the study of the physico-mechanical properties of composite materials with cement and clay matrices reinforced with Alfa and Diss fibers with dimensions ranging from 2 to 8 cm. This involves evaluating the performance of these materials according to the formulation, for a volume ratio (Alfa or Diss / Matrix fibers equal to 4), using dry fibers and pre-wetted fibers. The study of the mechanical properties showed a drop of the performance for both compression and bending strength compared to the reference material without adding fibers (cement or clay paste). It should be noted that the best mechanical performance is obtained for the case of composites materials with cementitious matrix with pre-wetted fibers. On the other hand, in the case of composites with clayey matrices, pre-wetting does not improve the mechanical characteristics. It is also noted that the best dimensions of fibers which improve the mechanical characteristics in bending are generally 6 cm for composites with a clay matrix and between 2 and 4 cm for cementitious composites. In all cases, the fibers in composite materials with cement or clay matrix create a bridging effect, making it possible to limit the progression of cracks during loading. This phenomenon gives to the various composite materials a ductile behavior.

Résumé: The experimental study aims to prevent the alkali-silica reaction (ASR) of mortars made with reactive aggregates, where the volume rates of cement ranging from 10% to 50% are substituted by mineral admixtures such as Granulated Slag, Natural Pozzolan and Silica Fume. Their effectiveness in countering the ASR adverse effects; such as weight and dimensional variations, the width and density of cracks and mechanical performance losses was studied. The results obtained show that the rate and the nature of the mineral admixtures influence their effectiveness, for Granulated Slag and Natural Pozzolan the ideal rate is 30%, for Silica Fume the 10% rate seems effective in countering ASR adverse effects. This effectiveness is ensured by the pozzolanic reaction favored by the high temperature of the test and the alkalinity of the system.

Résumé: Abstract: The use of natural fibers in clay matrices is a reinforcement technique used for centuries in construction. Natural fibers incorporated into cement matrices require various specific treatments to overcome the problem of incompatibility between natural fibers and cement paste, due to the sugars contained in the plant. This article is focused on optimization the dimensions of diss and alfa fibers in clay matrices based on mechanical properties. For this, we used fibers of these materials with dimensions of 4, 6 and 8 cm. The three-point bending and compression tests with measurement of deformations have shown that the composites have a very ductile behavior, due to the presence of natural fibers which really play the role of reinforcement for the composite, while the pure clay paste exhibits low resistance and fragile behavior. The dimensions of the fibers have a great influence on the mechanical behavior of the clay matrix composites, and it has been found that the fibers give the best flexural strengths between 6 and 8 cm, and that the compression increases considerably without damage to stresses around 12 MPa, this is due to the great capacity of the fibers to take up the lateral tensile stresses in composites.

Résumé: A significant concern when designing durable concretes structures is the risk of alkali silkai reaction (ASR). The cracks formed by ASR increase the permeability of concrete, reduce the strength and lower the economic lifetime of concrete. The use of mineral and chemical admixtures to prevent expansion due to the alkali-silica reaction (ASR) was first reported 40 to 50 years ago. In this paper, a comprehensive experimental research was carried out to prevent the damages and to be able to improve in concrete structures with the reactive aggregates by using the ground granulated blast-furnace slag (GGBFS) in the mixtures. Furthermore, the engineering properties of blast-furnace slag and the test methodology used in the research were presented and the research findings were also discussed.

Résumé: Diss is a wild vegetal species which can be found in plenty on the shores of the Mediterranean Sea. This fibrous plant can provide cement materials with reinforcement properties similar to classical steel or polypropylene reinforced concrete. However, good adhesion between fibers and cement is required for the fibrous strengthening. The objective of this study is to investigate two types of treatments for Diss-based fibers in order to assess their efficiency. The first treatment consists of extracting the sugars by distillation of the Diss fibers. The second treatment consists of waterproofing the Diss fibers to prevent water absorption. The compressive and flexural strength parameters of Diss-cement composite are used to assess the treatment performances.

Résumé: Le diss est une plante sauvage méditerranéenne, très fibreuse, renfermant un pourcentage élevé de silice à l’état amorphe. Les fibres naturelles incorporées dans des matrices cimentaires nécessitent divers traitements spécifiques pour pallier au problème d’incompatibilité entre les fibres naturelles et la pâte de ciment, à cause des sucres renfermés dans la plante. Nous avons pour cet effet, procédé à l’utilisation de ces fibres dans diverses matrices telles que matrice d’argile et/ou de chaux pour étudier l’effet l’incompatibilité fibres-matrices. Les essais de flexion trois points et de compression avec mesure des déformations ont montré que les composites ont un comportement très ductile, du à la présence des fibres de diss qui jouent réellement le rôle de renfort pour le composite. ABSTRACT. The diss is a Mediterranean wild plant, very fibrous, containing an high percentage of silica in an amorphous state. The natural fibres with cementing matrix require various specific treatments to mitigate the problem of incompatibility between natural fibres and the cement paste, because of the sugars contained in the plant. We have for this effect, process with the use of these fibres in various matrices such as stamps clay and/or lime to study the effect of this incompatibility matrix fibre. The three points flexion and compression with measurement of the deformations showed that the composites have a very ductile behavior, with the presence of the fibres of diss which play really the part of reinforcement for the composite. MOTS-CLÉS : Diss, Ampelodesma mauritanica, fibres naturelles, composites, ductilité, Résistance KEY WORDS: Diss, Ampelodesma mauritanica, natural fibres, composites, ductility, strength.

Résumé: Le Diss (Ampelodesmos mauritanicus, famille des Poacées) est une grande graminée répandue dans l’Afrique-du-Nord méditerranéenne et les régions sèches de la Grèce à l`Espagne. En France, on la trouve dans les départements des Alpes-Maritimes, du Var, de la Corse-du-Sud et de l’Hérault. Cette plante était utilisée auparavant dans la réalisation des habitations anciennes de ces régions en raison de ses qualités mécaniques et hydriques. L’utilisation d’une telle plante fibreuse dans une pâte cimentaire offre des résistances aux tractions très intéressantes, qui font de ce matériau léger un excellent remplissage pour les structures soumises aux efforts sismiques. L’objectif de nos travaux était l’élaboration des composites à base de Diss dans des matrices cimentaires. Le matériau végétal de base, très fibreux, présente une absorption de l’ordre de 90%. L’utilisation des fibres de Diss naturel broyé comme agrégat dans des matrices cimentaires présente un retard de prise assez considérable et des résistances très faibles, alors que les fibres présentent des résistances à la tension considérable. Pour améliorer la contribution des fibres dans les composites à base cimentaire, nous avons donc procédé au traitement par ébullition des fibres de Diss pour extraire les substances causes de la mauvaise liaison entre les fibres et la pâte de ciment. Nous avons constaté que le traitement à l’eau bouillie a été très efficace, et a bien amélioré les propriétés mécaniques du composite.

Résumé: The Diss (Ampelodesmos mauritanicus, family of Poaceae) is a very luxuriant plant growing in wild state around the Mediterranean North Africa and dry areas of Greece and Spain. It grows in France, mainly, in the departments of the Alpes-Maritimes, the Var, the South of Corsica and Herault. In the past, it was used as building material because of its mechanical and hydrous qualities.The purpose of this research is to determine the effects of treated and untreated of the vegetables fibres.The use of such a fibrous plant in a cementitious matrix leads to lightweight materials with very attractive tensile behavior that can be used as advantageous infill in structures subjected to seismic effects. The basic vegetable material, very fibrous and siliceous, presents indeed an absorption of about 90% that would be corrected by using optimum water/cement ratio. Moreover, we noted a considerable retardation of setting and very low resistances during the composite tests with natural crushed diss, despite the fact that the fibres have considerable tensile strength about 100 MPa. To improve the fibres contribution in cementitious composites, we have carried out a treatment by boiling the fibres of diss to extract the substances responsible for the bad connection between fibres and the cement paste. The Diss fibres were also prewetted before introduction into the mixer. This treatment will eliminate a loss in workability due rapid absorption, and improve mechanical properties. Thus diss fibres reinforcements in cimentitious composites having encouraging mechanical properties, which may expand the applicability of these composites as masonry units in constructions.

Résumé: The Diss (Ampelodesmos mauritanicus, family of Poaceae) is a very luxuriant plant growing in wild state around the Mediterranean North Africa and dry areas of Greece and Spain. It grows in France, mainly, in the departments of the Alpes-Maritimes, the Var, the South of Corsica and Herault. In the past, it was used as building material because of its mechanical and hydrous qualities. The use of such a fibrous plant in a cementitious matrix leads to lightweight materials with very attractive tensile behavior that can be used as advantageous filling materials for structures subjected to seismic effects. This study is focused on the optimisation of this kind of material on the basis of mechanical properties. The basic vegetable material, very fibrous and siliceous, presents indeed an absorption of about 90% that would be corrected. Moreover, we noted a considerable retardation of setting and very low resistances during the composite tests with natural crushed diss, despite the fact that the fibres have considerable tensile strength. To improve the fibres contribution in cementitious composites, we have carried out a treatment by boiling the fibres of diss to extract the substances responsible for the bad connection between fibres and the cement paste. The results obtained are encouraging and enable to foresee a later development of this material.

Résumé: In the building sector, issues related to sustainable development have become a major concern. The choice of materials has fundamental importance since it has a considerable influence on the energy consumption of the building and also on the overall environmental impact of the construction. Materials reinforced with vegetable fibres and/or particles are currently considered amongst the most promising materials in sustainable engineering technologies due to their several potential applications. In addition to its sustainable credentials, the application of these elements is interesting as they exhibit a set of important advantages, such as wide availability at relatively low cost, bio-renewability, ability to be recycled, biodegradability, non-hazardous nature, zero carbon footprint, and interesting hygro-thermal and mechanical properties. The viability of using vegetable Diss fibers for developing a sustainable lightweight construction material was investigated in this paper. The produced specimen contained 4/1 volume ratio of Diss fibers to Binder. In order to mitigate the inhibitory effect exerted by vegetable materials on binder hydration, Diss fibers were treated with hot water, while air lime-based Tradical PF70 binder has been selected to replace traditionally used cementitious binder. The study conducted on hardened material properties has indicated that despite a significant reduction in mechanical strength, the material exhibits higher residual stress that highlighted a ductile behaviour, compared to the reference specimen containing neat binder without Diss fibers

Résumé: L'effet de la substitution progressive de 10 % à 50 % du volume de ciment par le laitier granulé et la pouzzolane naturelle sur les propriétés physicomécaniques des pâtes et des mortiers à base de verre recyclé a été étudié. L'effet de ces additions sur la consistance et les temps de prise des pâtes de ciment ainsi que sur les propriétés physiques et mécaniques des mortiers a été determiné. L’effet inhibiteur de la réaction alcali- silice (RAS) par l'essai accéléré sur mortier a éré aussi vérifié. L'utilisation du laitier granulé et de la pouzzolane naturelle engendre l'augmentation des temps de prise des pâtes de ciment. Elle provoque aussi un besoin en eau important. Elle améliore les propriétés mécaniques et la rigidité des mortiers et peut réduire les expansions et les pertes de performance mécaniques dues à la RAS.

Résumé: Construction field has to play an important role in resolving environmental problems related to recycling and exploitation of the biomass. In the category of cementitious materials, various types of wastes and byproducts derived from agriculture have already been used, either as particles, in total or partial replacement of mineral aggregates, or as fibers for reinforcement. In this study we were interested at the potential use of jute fibers as reinforcing elements for mortars. The jute fiber was used in partial replacement of sand at different rates; the control mortar was without fibers. A Memorandum of experimental tests was conducted in order to study the composite in fresh and hardened state. The chemical compatibility of jute fibers with cement was evaluated using tests of hydration which consist in recording the temperature rise in the heart of the composite during the exothermic reactions between the components of the cement and the mix water. The results of these tests revealed very low index of inhibition confirming the compatibility of the jute fiber with cement. The mechanical tests showed a decrease in performances according to the increase of fiber and a substantial gain weight.

Résumé: The Diss (Ampelodesmos mauritanicus, family of Poaceae) is a very luxuriant plant growing in wild state around the Mediterranean North Africa and dry areas of Greece and Spain. It grows in France, mainly, in the departments of the Alpes-Maritimes, the Var, the South of Corsica and Herault. In the past, it was used as building material because of its mechanical and hydrous qualities. The use of such a fibrous plant in a cementitious matrix leads to lightweight materials with very attractive tensile behavior that can be used as advantageous filling materials for structures subjected to seismic efforts. This paper is focused on the optimisation of this kind of material on the basis of mechanical and hydrous properties. The basic vegetable material, very fibrous, presents indeed an absorption of about 90% that would be corrected. Moreover, we noted during the composite tests with natural crushed diss a considerable retardation of setting and very low resistances, despite the fact that the fibres have considerable tension strength. To improve fibres contribution in cementitious composites, we have carried out the treatment by boiling the fibres of diss to extract the substances responsible for the bad connection between fibres and the cement paste. We have also carried out treatments with the linseed oil, and the bitumen to attenuate the fibres absorption rate. The results obtained are encouraging and enable to foresee a later development of this material.