Study of Mortars Made with Natural and Artificial Pozzolans

The objective of this work is to evaluate the thermal activation potential of clay soils, particularly the clay fraction of dam mud, for the production of artificial pozzolan which can be substituted to cement in concrete and mortars applications and also to make a comparative study with the natural pozzolan available in the area of Beni Saf in considerable quantities. The research study is carried out on three mortars 10, 20 and 30% of natural pozzolan of Beni Saf and artificial pozzolan from the mud calcined at 850 ° C / 3 hours of the dredged sediments of the dams of Fergoug and Ouizert, and on a control mortar without additions for the need of comparison. Several physical, mechanical, microstructural and sustainable tests have been carried out to carry out this research study: maneuverability in the fresh state, impeded shrinkage, mechanical performance, absorption, acid attack (5% CH3COOH, 5% HNO3 and 5% H2SO4), mass loss and pH reading follow-up in the hardened state. Compressive strengths indicate that pozzolan-based mortars have the best results in particular over the long term, whereas the results of acid attack tests show that the calcined mud has a significantly greater influence than natural pozzolan

Prevention of alkali silica reaction risks in mortars by mineral admixtures.

Cette étude expérimentale a pour but de prévenir la réaction alcali-silice (RAS) des mortiers formulés avec des granulats réactifs, où on substitue des taux volumiques de ciment allant de 10% à 50% par des additions minérales telles que le laitier granulé, la pouzzolane naturelle et la fumée de silice. Leur efficacité à contrer les effets néfastes de la RAS, tel que les variations pondérales et dimensionnelles, la largeur et la densité des fissures et les pertes des performances mécaniques ont été étudiés.Les résultats obtenus montrent que le taux et la nature de l'addition influent sur leur efficacité. Pour le laitier granulé et la pouzzolane naturelle le taux idéal est 30%, pour la fumée de silice le taux 10%semble efficace à contrer les effets néfastes de la RAS. Cette efficacité est assurée par la réaction pouzzolanique favorisée par la haute température de l'essai et l'alcalinité du système.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

Prevention of alkali silica reaction risks in mortars by mineral admixtures.

Cette étude expérimentale a pour but de prévenir la réaction alcali-silice (RAS) des mortiers formulés avec des granulats réactifs, où on substitue des taux volumiques de ciment allant de 10% à 50% par des additions minérales telles que le laitier granulé, la pouzzolane naturelle et la fumée de silice. Leur efficacité à contrer les effets néfastes de la RAS, tel que les variations pondérales et dimensionnelles, la largeur et la densité des fissures et les pertes des performances mécaniques ont été étudiés.Les résultats obtenus montrent que le taux et la nature de l'addition influent sur leur efficacité. Pour le laitier granulé et la pouzzolane naturelle le taux idéal est 30%, pour la fumée de silice le taux 10%semble efficace à contrer les effets néfastes de la RAS. Cette efficacité est assurée par la réaction pouzzolanique favorisée par la haute température de l'essai et l'alcalinité du système.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

Properties of construction material based-Diss fibers: Physico-mechanical characterisation

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

Study of Mortars Made with Natural and Artificial Pozzolans

The objective of this work is to evaluate the thermal activation potential of clay soils, particularly the clay fraction of dam mud, for the production of artificial pozzolan which can be substituted to cement in concrete and mortars applications and also to make a comparative study with the natural pozzolan available in the area of Beni Saf in considerable quantities. The research study is carried out on three mortars 10, 20 and 30% of natural pozzolan of Beni Saf and artificial pozzolan from the mud calcined at 850 ° C / 3 hours of the dredged sediments of the dams of Fergoug and Ouizert, and on a control mortar without additions for the need of comparison. Several physical, mechanical, microstructural and sustainable tests have been carried out to carry out this research study: maneuverability in the fresh state, impeded shrinkage, mechanical performance, absorption, acid attack (5% CH3COOH, 5% HNO3 and 5% H2SO4), mass loss and pH reading follow-up in the hardened state. Compressive strengths indicate that pozzolan-based mortars have the best results in particular over the long term, whereas the results of acid attack tests show that the calcined mud has a significantly greater influence than natural pozzolan

Viability of flax particles to develop cellular construction materials: Physico-mechanical characterisation

The problems related to environmental issues have motivated extensive research on environmentally friendly materials. The built environment is responsible for high primary energy use and more of energy related CO2 emissions. However, it is important to develop low-embodied energy, carbon-negative, sustainable construction materials to replace conventional products. In this context, agricultural wastes are the excellent alternative materials to substitute mineral aggregates because they are widespread and easily accessible. The application of these elements is interesting as regards the recycling of the vegetable particles, since these are easily available and renewable low-cost raw materials, and has advantage for economy and environment. However, the reduction of energy consumption in construction, production of thermal insulation materials, and the solution of environmental problems by recycling waste are becoming greater problems. Various types of agriculture waste, after being processed, have been used as particles in concrete or mortars. These materials display lower density and have several potential applications such as acoustic and thermal insulation, fire resistance cladding…etc. The study reported in this paper was undertaken to investigate the physico-mechanical properties of cellular materials based on flax particles, in order to produce usable materials in cellular concrete applications. The material produced containing different volumes of flax particles (0V (control mortar), 1V, and 2V) was lightened by creating a porous structure in the matrix through a chemical reaction between aluminium powder and free lime. A study conducted on hardened material properties has indicated a significant reduction in sample unit weight, thereby resulting in a level of compressive strength compatible with a load-bearing wall. The reduction in flexural strength was lower than that in compressive strength. These results shown that the cellular material based on flax particles can be used as suitable insulated load-bearing walls

Abrasion resistance of sustainable green concrete containing waste tire rubber particles

The development of new environmental friendly concretes such as rubberized concrete is being promoted due to the environmental problems created by the waste tire rubber. Every year millions of tires are discarded, thrown away or buried all over the world, representing a very serious threat to the ecology. In this study, we analyse the potential of waste tire rubber particles as a partial substitute for fine aggregates in normal strength and high strength cement concrete and the resistance to abrasion has been measured. Statistical Analysis was carried out to strengthen the results obtained from experiments. The results show that the use of tire rubber particles can improve the abrasion resistance of concrete, and this can ensure its applications in pavements, floors and concrete highways, or in places where there are abrasive forces between surfaces and moving objects. (C) 2016 Elsevier Ltd. All rights reserved

Etude de la faisabilité d'un composite à matrice cimentaire renforcé de fibres de jute

Le domaine de la construction doit jouer un rôle important dans la résolution des problèmes environnementaux lies au recyclage et l'exploitation de la biomasse. Dans la catégorie des matériaux cimentaires, différents types de déchets et coproduits issus de l'agriculture ont déjà été utilises, soit sous forme de particules, en remplacement total ou partiel des granulats minéraux, soit sous forme de fibres pour renforcement. Dans cette, étude nous nous sommes intéresses au potentiel d'utilisation des fibres de jute comme éléments de renfort pour mortiers. La fibre de jute a été utilisée en substitution partielle du sable à différents taux, le mortier de référence étant sans fibres. Un protocole d'essais expérimentaux à été mène pour étudier les composites a l'état frais et a l'état durci. La compatibilité chimique des fibres de jute avec le ciment à été évaluée a l'aide des tests d'hydratation qui consistent a enregistrer l'élévation de température au cœur du composite lors des réactions exothermiques des composants du ciment avec l'eau de gâchage. Les résultats révèlent un faible indice d'inhibition confirmant la compatibilité de la fibre avec le ciment. Les essais mécaniques montrent une baisse des performances avec l'augmentation du taux de fibres, mais un gain substantiel en poids.Mots clés: Composite cimentaire - Mortier de fibres - Fibres de jute - Compatibilité chimique. 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.Keywords: Cementitious composite - Fiber mortars - Jute fibers - Chemical compatibility

Comportement mécanique et hydrique des composites à matrice cimentaire et argileuse à base de diss «Ampelodesma mauritanica»

L’objectif de cette étude porte sur l’examen des potentialités de l’utilisation de fibres de diss broyé, dans une matrice cimentaire, en vue de l’utilisation du composite dans le domaine d’application des bétons légers. Par ailleurs, l’ajout de matières lignocellulosiques entraîne une inhibition de la réaction d’hydratation du ciment, due au relargage de substances hydrosolubles renfermées dans le végétal. Ce phénomène se manifeste par un retard dans la prise, qui affecte le durcissement du composite. Pour pallier cet effet inhibiteur, les fibres de diss ont subi un traitement thermique, et ce afin de neutraliser le relargage des sucres et des constituants hydrosolubles renfermés dans le végétal. Ce phénomène d’incompatibilité du végétal avec des matrices argileuses n’a pas été observé. Des essais comparatifs entre les composites à base de diss naturel et de diss bouilli à matrice cimentaire ont été réalisés pour déterminer les résistances mécaniques

Approche du comportement dynamique d'un oxyde liquide dans un matériau composite autocicatrisant MAC

Les matériaux composites à matrice céramique CMC, sont généralement formés d au moins deux matériaux ayant une forte capacité d adhésion. Ces matériaux sont principalement composés de renforts fibreux assurant la tenue mécanique de la structure et d une matrice qui permet sa cohésion. Utilisées principalement dans le domaine de l aéronautique, elles sont reconnues pour leur bonne tenue mécanique, leur réfractarité élevée tout en conservant une densité faible. Par contre, l inconvénient majeur associé à ces matériaux est l apparition de fissures qui sont dues soit au procédé de fabrication soit aux sollicitations mécaniques externes.Dans ce travail, une attention toute particulière est consacrée aux composites à matrice auto-cicatrisante dont la principale propriété est l'aptitude à "réparer" les effets de la fissure par formation d'un verre visqueux.Ces verres visqueux se forment au sein de la fissure grâce à l oxydation des éléments qui constituent la matrice. Selon la température, différents verres peuvent être formés.Leur fonction est de reboucher les fissures de taille micrométrique de façon à ralentir la diffusion de l'oxygène en direction des fibres et éviter leur rupture par oxydation.Cependant, pour des systèmes en rotation rapide tels que les turbines basse pression des moteurs d avion (pièce étudiée actuellement), on peut s'interroger quant à la mobilisation du verre visqueux cicatrisant dans un système complexe géométriquement et inhomogène du point de vue de la nature des surfaces. Pour approcher le comportement du verre cicatrisant dans un système modèle mais néanmoins réaliste, une approche de modélisation numérique a été entreprise. L'outil numérique utilisé pour cette étude est le code de calcul Thétis développé à l I2M. Celui-ci est adapté à ce type de simulation puisqu'il permet la modélisation d'écoulements diphasiques incluant des phénomènes physiques complexes tels que le mouillage. Ainsi, l'objectif de ce travail est-il de déterminer les limites d'utilisation de ce type de matériau en fonction des conditions auxquels il est soumis en évaluant la mobilité du verre cicatrisant dans la fissure.The Ceramic Matrix Composites (CMCs) are generally formed of at least two materials having strong adhesion ability. These materials are mainly composed of fibrous reinforcement which ensures the mechanical resistance of the structure and a matrix which allows its cohesion.Used mainly in aerospace, the CMCs are highly valued for their good mechanical strength, their good refractory properties associated with a low density.However, the major drawback of these materials is cracks formation due to manufacturing process or to external mechanical stresses.In this study, we focus on composite materials having self-healing properties. These materials have the ability to produce healing viscous glasses in presence of oxygen.These viscous glasses are formed in the crack under the influence of oxidation of matrix compounds. Depending on the temperature level, glasses of different natures are formed.Their main role is to reseal the micrometric cracks, to limit oxygen access to the fibers in order to prevent their rupture by oxidation.However, for fast rotating systems such as the low pressure turbine of aircraft engines, we may question about mobilization of such a viscous glass in a system characterized by a complex geometry and chemically inhomogeneous surfaces.Therefore, a numerical approach was undertaken, using "Thetis" software. Developed at I2M, this software allows us modelling two-phase flow in model simplified geometry (reflecting however reality) including complex phenomena such as wetting. Numerical results yield to the determination of operating limitations of CMCs in terms of healing efficiency as a function of external mechanical stresses (rotation) and crack geometry.BORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF