Effects of thermal damage on physical properties and cracking behavior of ultrahigh-performance fiber-reinforced concrete

International audienceIn this work, we study the impact of thermal damage on the physical and mechanical properties of ultrahigh-performance fiber-reinforced concrete (UHPFRC), especially on their cracking process under compressive loading. Four mixtures of UHPFRC were prepared using identical composition but reinforced with different types of fibers: mineral fibers (Steel or Wollastonite) or organic fibers (PP or PVA) and compared with that without fibers (UHPC). To induce a thermal damage on UHPFRC, the samples were subjected to temperatures ranging from 150 to 400 °C. After each degradation stage, the gas permeability and the P-wave velocity were measured. The mechanical behavior under loading has been studied using a uniaxial compression test which combines the gas permeability and the acoustic emission measurement. The results show that the melting of organic fibers at approximately 180 °C builds a tunnel across the cement paste and increases brutally the gas permeability. At 400 °C treatment, a decrease of compression strength by 30 % and of Young modulus by approximately 60 % was observed. However, we can see that the thermal damage results a decrease in the threshold of initial cracking (rk-ci) and that of unstable cracking (rk-pi), and this can be explained by the initiation of new cracks and their coalescence

Comportement de matériaux constitutifs de barrages en enrochement : caractérisation minéralogique, physique, mécanique et altérabilité

CE TRAVAIL DE THESE RENTRE DANS LE CADRE D UNE PROBLEMATIQUE GENERALE QUI PORTE SUR L ETUDE DU VIEILLISSEMENT DE BARRAGES EN ENROCHEMENT APPARTENANT AU PARC HYDROELECTRIQUE D EDF. LE TRAVAIL DE RECHERCHE REALISE A EU POUR OBJECTIF D ETUDIER LE COMPORTEMENT DES MATERIAUX CONSTITUTIFS DE CES BARRAGES ET D EXAMINER LEUR CARACTERE EVOLUTIF.LA CARACTERISATION DES MATERIAUX PRELEVES A PORTE SUR LES ASPECTS SUIVANTS : (I) UNE CARACTERISATION MINERALOGIQUE DONT LES OBJECTIFS SONT LA DETERMINATION DE LA COMPOSITION MINERALOGIQUE, L OBSERVATION DE LA FISSURATION, LA DESCRIPTION DE L ALTERATION ET LA RECHERCHE D UNE EVENTUELLE PRESENCE DE MINERAUX EVOLUTIFS. (II) UNE CARACTERISATION MULTIPHYSIQUE. (III) UNE CARACTERISATION MECANIQUE PAR LA DETERMINATION DES PRINCIPALES PROPRIETES MECANIQUES MACROSCOPIQUES ET L ETUDE DU COMPORTEMENT SOUS CHARGE.POUR L ETUDE DE L ALTERABILITE, SOUS FACTEURS DE DEGRADATION PHYSIQUES ET/OU PHYSICO-CHIMIQUES, LES RESULTATS OBTENUS ONT MONTRE QUE LES MATERIAUX ETUDIES SONT SUSCEPTIBLES D EVOLUER MEME SOUS L EFFET D UNE ALTERATION MODEREE.IN THIS WORK, MATERIALS OF A CONCRETE FACE ROCKFILL DAMS -CFRD- ARE STUDIED. FIRSTLY, THE ROCKFILL MATERIALS ARE CHARACTERIZED BY MEASUREMENT OF THEIRS MINERALOGICAL, PHYSICAL AND MECHANICAL PROPERTIES. THE FAILURE PROCESS UNDER COMPRESSIVE LOADING IS ALSO INVESTIGATED. THE MECHANICAL BEHAVIOR ANALYSIS OF MATERIAL SPECIMEN SUBJECTED TO COMPRESSIVE LOADING IS ACHIEVED BY MEASURING SIMULTANEOUSLY, DURING THE LOADING PATH, THE DEFORMATIONS, THE GAS PERMEABILITY VARIATIONS AND THE ACOUSTIC EMISSION. SECONDLY, ROCK SPECIMENS ARE SUBJECTED TO PHYSICAL AND PHYSICO-CHEMICAL WEATHERABILITY TESTS TO EVALUATE THEIR DURABILITY. IN FACT, IN THIS TYPE OF DAM THE DURABILITY EVALUATION OF ROCK IS VERY IMPORTANT WHEN THE MATERIALS ARE TO BE SUBJECTED TO THE NATURAL ELEMENTS, SEASONAL WEATHER, REPEATED CYCLES OF TEMPERATURE, FREEZE, THAW, AND SERVICE CONDITIONS. RESULTS OF WEATHERABILITY TESTS SHOW THAT THE BEHAVIOR OF STUDIED ROCKFILL MATERIALS CAN BE AFFECTED EVEN IN MODERATED CONDITIONS.RENNES-INSA (352382210) / SudocSudocFranceF

Temperature Effects on Physical Properties and Mechanical Behavior of Granite: Experimental investigation of Material Damage

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Etude expérimentale de l'endommagement thermique du granite: Mesures destructives et non destructives

International audienceIn this paper, the effect of thermal treatment on physical and mechanical properties of a granitic rock is experimentally investigated. Gas permeability, P-wave velocity and attenuation, ultimate strength and Young modulus are measured on samples heated at temperature ranging from 105 to 600°C. Results show good correlation between the evolution of these properties and the amount and nature of the damage induced by the thermal treatment. The effect of temperature on the failure process in granite is also investigated using strain gauge measurements and permeability evolution in uniaxial compressive test.L'objectif de ce travail est d'étudier l'effet de la température sur les propriétés physiques et mécaniques d'un matériau granitique. Des mesures de perméabilité au gaz, de vitesse de propagation des ondes longitudinales, de résistance mécanique à la compression et le module de Young ont été réalisées sur des échantillons sains et traités à des températures croissantes de 105°C à 600°C. Les résultats montrent une très bonne corrélation entre l'évolution de ces propriétés et l'endommagement induit par le traitement imposé. Cette étude est approfondie par une investigation de l'évolution du processus de rupture par analyse des courbes contrainte-déformations et contrainte-perméabilité

Damage in granite under heating/cooling cycles and water freeze-thaw condition

International audienc

MONITORING OF TIMBER STRUCTURES: MOISTURE CONTENT EVALUATION BY USING ELECTRICAL RESISTIVITY METHOD

International audienceIn addition to hygro-mechanical dependency, moisture is a major factor that influence fungal growth, hence the service life durability of wood-based structures. Degradations related to environment aggressions can lead to various damages. Thus, the management of wooden structures requires the development of maintenance strategies associated with appropriated inspection techniques. Non-Destructive Testing (NDT) tools has received more attention from academic researches and manufactures in the last decades in order to establish an optimal and reliable diagnostic of the hydric state of these structures. One of the most common and most easily applicable methods is electrical resistivity measurement. The approach-based tool is essentially a megohmmeter measuring the electrical resistance of wood. It is measured using electrodes which are composed of one or more pairs of needle-shaped probes embedded in the wood. Our study deals with the evaluation of moisture content distribution in timber structures using an electrical resistivity approach, usually developed in geophysics and mainly based on the adaptation of multiplexed methods used for electrical prospecting measurements. This study aims to present an experimental and numerical approaches to evaluate resistivity measurements efficiency. Therefore, a parametric study was set up to analyze the effect of some of the most important experimental variables (species, type of electrode, electrode configurations) on resistance measurements. The results of this research are argued and analyzed to define the operational limits related to measuring tool capacities and wood properties. An experimental data sorting algorithm was implemented to exploit an extensive database and to optimize the numerical inversion procedure accordingly. First measurements on a timber construction are also presented to highlight the experimental strategy concerning in-situ monitoring

Characterization of failure process in concrete using helium gas permeability measurement under compressive loading

International audienc

Influence of thermal damage on physical properties of a granite rock: Porosity, permeability and ultrasonic wave evolution

International audienc

MONITORING OF TIMBER STRUCTURES: MOISTURE CONTENT EVALUATION BY USING ELECTRICAL RESISTIVITY METHOD

International audienceIn addition to hygro-mechanical dependency, moisture is a major factor that influence fungal growth, hence the service life durability of wood-based structures. Degradations related to environment aggressions can lead to various damages. Thus, the management of wooden structures requires the development of maintenance strategies associated with appropriated inspection techniques. Non-Destructive Testing (NDT) tools has received more attention from academic researches and manufactures in the last decades in order to establish an optimal and reliable diagnostic of the hydric state of these structures. One of the most common and most easily applicable methods is electrical resistivity measurement. The approach-based tool is essentially a megohmmeter measuring the electrical resistance of wood. It is measured using electrodes which are composed of one or more pairs of needle-shaped probes embedded in the wood. Our study deals with the evaluation of moisture content distribution in timber structures using an electrical resistivity approach, usually developed in geophysics and mainly based on the adaptation of multiplexed methods used for electrical prospecting measurements. This study aims to present an experimental and numerical approaches to evaluate resistivity measurements efficiency. Therefore, a parametric study was set up to analyze the effect of some of the most important experimental variables (species, type of electrode, electrode configurations) on resistance measurements. The results of this research are argued and analyzed to define the operational limits related to measuring tool capacities and wood properties. An experimental data sorting algorithm was implemented to exploit an extensive database and to optimize the numerical inversion procedure accordingly. First measurements on a timber construction are also presented to highlight the experimental strategy concerning in-situ monitoring

Adaptation of the micro-deval test for assessing the surface weathering degree of granite

International audienc