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

Valorisation de déchets de caoutchouc dans les matériaux de construction : cas d’un composite cimentaire cellulaire

In this work, the idea is to use rubber waste particles as a raw material, to develop a new lightweight construction materials. The objective of the research reported in this paper is to investigate the physico-mechanical properties of Aerated Cement-Rubber Composites (ACRC), based on rubber particles. The volume content ratio of the rubber particles ranged from 0% to 50%. The aerated composite was produced using a new type of proteinic air-entraining agent, in accordance with a specific aerating process derived in the laboratory. The aerated composite was produced to be used in cellular concrete applications. Results from tests performed on fresh aerated composites have demonstrated many attractive properties, such as improved workability and a high stability of air bubbles within the matrix. A study conducted on hardened composite properties has indicated a significant reduction in sample unit weight, thereby resulting in a level of compressive strength. The composite satisfies the basic requirement of construction materials, and could be used for insulated load-bearing wall this study has also highlighted the effect of the proteinic air-entraining agent on the cementrubber interaction system, as regards the composite’s compressive strength. However, an examination of the composite’s water capillary absorption reveals that the addition of rubber particles tends to restrict water propagation and reduce water absorption; sorptivity values decrease with increasing rubber particles content.Cette étude concerne l’évaluation des propriétés du composite cellulaire ciment-caoutchouc, élaboré à base de poussières de caoutchouc pour des teneurs allant de 0 à 50 %. L’allégement a été effectué suivant un procédé d’allégement par moussage protéinique, mis au point au laboratoire, en vue de l’utilisation du composite dans le domaine d’application des bétons cellulaires. L’étude du composite à l’état frais a montré une amélioration de la maniabilité, avec une bonne stabilité des bulles d’air dans la matrice. L’étude du composite à l’état durci a montré une nette réduction de la masse volumique, avec des propriétés mécaniques compatibles avec l’utilisation en isolant porteur. L’effet de l’agent entraîneur d’air protéinique sur les liaisons matrice/caoutchouc dans la résistance du composite a été mis en évidence. L’étude de l’absorption par capillarité du composite a montré que l’ajout de poussières de caoutchouc réduit la sensibilité à l’eau du composite

Moisture hysteresis influence on mass transfer through bio-based building materials in dynamic state

International audienceBio-based materials are increasingly present in the constitution of the building envelops thanks to their numerous advantages such as good thermo-hygric performances, weak environmental impact, efficient regulation of the perceived indoor air quality and human comfort... The analysis of moisture transfer is necessary to increase the efficiency of these materials and to ensure building sustainability. Actually, most of hygrothermal models neglect the moisture hysteresis effect, arguing the weak impact on the obtained results. Thus, a 3D numerical model was built on COMSOL Multiphysics, taking into account the hysteresis phenomenon to assess the impact of hysteresis effects. The model was validated thanks to experimental tests performed on hemp concrete and rape straw concrete. Tests were carried out under various dynamic hygric solicitations, with a regulated climatic chamber. The results have been compared in steady and transient states, with and without the effect of moisture hysteresis. Results have shown that hysteresis could be neglected in steady state, if the relative humidity range did not reach the capillary condensation. In this case, a model based on the main adsorption isotherm could lead to reasonable approximation, with weak calculation costs. For the analysis of a wall under real climatic solicitations, which corresponds to a non-steady state, neglecting the moisture hysteresis could lead to significant discrepancies, especially in terms of sample moist mass (and consequently moisture content or absolute humidity). (C) 2018 Elsevier B.V. All rights reserved

Assessment of hygrothermal behavior of newly straw-rape concrete material in various conditions

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EpiBrainRad An epidemiologic study of the neurotoxicity induced by radiotherapy in high grade glioma patients

International audienceBackground Radiotherapy is one of the most important treatments of primary and metastatic brain tumors. Unfortunately, it can involve moderate to severe complications among which leukoencephalopathy is very frequent and implies cognitive deficits such as memory, attention and executive dysfunctions. However, the incidence of this complication is not well established and the risk factors and process are poorly understood. The main objective of the study is to improve knowledge on radio-induced leukoencephalopathy based on pluridisciplinar approaches combining cognitive, biologic, imagery and dosimetric investigations. Method/Design The EpiBrainRad study is a prospective cohort study including newly diagnosed high grade gliomas patients treated by radiotherapy and concomitant-adjuvant temozolomide chemotherapy. Patients are included between their surgery and first day of radio-chemotherapy, and the follow-up lasts for 3 years after treatment. Cognitive functioning assessments, specific blood biomarkers measures and magnetic resonance imagery are performed at different moment during the follow-up, and a specific dosimetric assessment of organs involved in the beam fields is performed. Firstly, leukoencephalopathy incidence rate will be estimated in this population. Secondly, correlations between cognitive impairments and dosimetry, biomarkers ranges and anomalies on imagery will be analyzed in order to better understand the onset and evolution of cognitive decrement associated with radiotherapy. Furthermore, a new cognitive test, quickly and easily performed, will be studied to determine its sensibility to detect leukoencephalopathy decrement. Discussion With an original multidisciplinary approach, the EpiBrainRad study aims to improve knowledge on radio-induced leukoencephalopathy in order to improve its early diagnosis and prevention. The main challenge is to preserve quality-of-life after cancer treatments which imply to study the incidence of radiation-induced complications and their associated risk factors. Trial Registration NCT02544178 © 2015 Durand et al