HAL (Le Centre pour la Communication Scientifique Directe), 2018
L’ecaillage des betons est un phenomene brutal pouvant etre prejudiciable pour la stabilite d'... more L’ecaillage des betons est un phenomene brutal pouvant etre prejudiciable pour la stabilite d'une structure pendant et apres un incendie. Ce phenomene depend de la composition du materiau, du chargement thermique mais aussi du changement mecanique applique. Ces dernieres annees, des etudes theoriques et experimentales ont tente d'examiner les causes possibles de l'ecaillage des betons. En particulier, de nombreuses discussions autour de l'importance relative des mecanismes thermomecaniques et thermohydriques ont ete menees. Afin de mieux comprendre l'effet du chargement mecanique sur l'ecaillage des essais feu ISO ont ete conduits sur des dalles sollicitees en compression biaxiale. Des calculs thermomecaniques (TM), reproduisant le deroulement des essais, ont ete effectues avec le code aux elements finis CAST3M. Le travail realise a permis de bien predire a la fois l'evolution des temperatures mais aussi des deplacements dans les dalles.
This study focus on the effects of both water content and cement stabilization on the fire behavi... more This study focus on the effects of both water content and cement stabilization on the fire behavior of earth bricks. To observe the effect of cement stabilization, two materials are formulated: raw earth with only soil and water, and stabilized bricks with soil, water and cement (3.5% by mass of soil). Since the material’s mechanical strength can strongly influence its fire behavior, the raw bricks were compacted at 50 MPa to reach a compressive strength similar to the one of stabilized bricks. Four different water contents were tested; dry state obtained with oven drying and three others achieved through equalization at 50%, 75% and 100% of relative humidities. Bricks are then subjected to an ISO 834-1 standard fire. Results show that water content has caused a thermal instability behavior on the raw earth bricks after equalization at 50% and 75% relative humidities. Thermally stable bricks displayed a noticeable diffusion of cracks on their heated face. Furthermore, cement stabili...
Permeability is related to the interconnectivity of the pores in the concrete, which measures how... more Permeability is related to the interconnectivity of the pores in the concrete, which measures how fast the gases or liquids will flow through it due to a pressure gradient. Knowledge of permeability will allow us to better understand the fluid transport behaviour in concrete, which could influence its fire spalling behaviour by directly influencing the build-up of pore pressure during heating. Three different gas permeability tests were carried out in SIAME and CSTB on 2 concretes B40-II (3% of slag) and B40-III (43% of slag). They are as follows: i) Residual axial permeability tests under radial confining pressure after unloaded preheating, ii) Residual axial permeability tests under radial confining pressure after preheating under uniaxial loading and iii) Residual radial permeability tests under uniaxial loading. The experimental test results have clearly shown that the presence of loading and their levels have a significant influence on the permeability of concrete. The permeability increase or decrease depends on the orientation and opening of cracking and these two parameters are influenced by compressive loading. The permeability of B40-III (much higher amount of slags) is more sensitive than B40-II in all heating and loading conditions
L’ecaillage des betons est un phenomene brutal pouvant etre prejudiciable pour la stabilite d'... more L’ecaillage des betons est un phenomene brutal pouvant etre prejudiciable pour la stabilite d'une structure pendant et apres un incendie. Ce phenomene depend de la composition du materiau, du chargement thermique mais aussi du changement mecanique applique. Ces dernieres annees, des etudes theoriques et experimentales ont tente d'examiner les causes possibles de l'ecaillage des betons. En particulier, de nombreuses discussions autour de l'importance relative des mecanismes thermomecaniques et thermohydriques ont ete menees. Afin de mieux comprendre l'effet du chargement mecanique sur l'ecaillage des essais feu ISO ont ete conduits sur des dalles sollicitees en compression biaxiale. Des calculs thermomecaniques (TM), reproduisant le deroulement des essais, ont ete effectues avec le code aux elements finis CAST3M. Le travail realise a permis de bien predire a la fois l'evolution des temperatures mais aussi des deplacements dans les dalles.
The paper presents the results of a study on the impact of high temperature on compressive streng... more The paper presents the results of a study on the impact of high temperature on compressive strength and ultrasonic pulse velocity in ordinary (OC) and high performance concrete (HPC). The relationship between concrete residual compressive strength (f cT) and ultrasonic pulse velocity (V T) was investigated and a regression curves f cT (V T) having the similar logarithmic character was proposed. The basic curve proposed in the standard EN 12504-4 appears to be not appropriate in describing the dependency f cT = f(V T) for heated concrete. Due to the basic curve limitation to ultrasonic pulse velocities ranging between 4.0 and 4.8 km/s, its practical implementation for heated concretes seems to be limited. In this study most of V T values even for concrete samples heated to 200 °C were below the value of 4.0 km/s. In the paper the damage extent in thermally affected concrete element was also investigated with exponential transducers using point-by-point analyses on cored samples.
ABSTRACT This paper presents the results of an experimental study carried out on an ordinary conc... more ABSTRACT This paper presents the results of an experimental study carried out on an ordinary concrete. An original equipment allowed us to carry out compression tests at high temperatures by measuring the longitudinal and radial strains of the samples. A first series of hot compression tests allowed us to determine the stress/strain curves of the material at the various temperatures as well as the evolution of compressive strength with the temperature. Short-term creep tests were carried out at various temperatures. The recovery of material was also measured. The influence of certain parameters was studied: heating rate and preheating. At last, Thermal Strain Under Load tests allowed us to calculate the Transient Thermal Strains (TTS) of the material. The influence of certain parameters on the TTS was studied: heating rate, preheating.
HAL (Le Centre pour la Communication Scientifique Directe), 2018
L’ecaillage des betons est un phenomene brutal pouvant etre prejudiciable pour la stabilite d'... more L’ecaillage des betons est un phenomene brutal pouvant etre prejudiciable pour la stabilite d'une structure pendant et apres un incendie. Ce phenomene depend de la composition du materiau, du chargement thermique mais aussi du changement mecanique applique. Ces dernieres annees, des etudes theoriques et experimentales ont tente d'examiner les causes possibles de l'ecaillage des betons. En particulier, de nombreuses discussions autour de l'importance relative des mecanismes thermomecaniques et thermohydriques ont ete menees. Afin de mieux comprendre l'effet du chargement mecanique sur l'ecaillage des essais feu ISO ont ete conduits sur des dalles sollicitees en compression biaxiale. Des calculs thermomecaniques (TM), reproduisant le deroulement des essais, ont ete effectues avec le code aux elements finis CAST3M. Le travail realise a permis de bien predire a la fois l'evolution des temperatures mais aussi des deplacements dans les dalles.
This study focus on the effects of both water content and cement stabilization on the fire behavi... more This study focus on the effects of both water content and cement stabilization on the fire behavior of earth bricks. To observe the effect of cement stabilization, two materials are formulated: raw earth with only soil and water, and stabilized bricks with soil, water and cement (3.5% by mass of soil). Since the material’s mechanical strength can strongly influence its fire behavior, the raw bricks were compacted at 50 MPa to reach a compressive strength similar to the one of stabilized bricks. Four different water contents were tested; dry state obtained with oven drying and three others achieved through equalization at 50%, 75% and 100% of relative humidities. Bricks are then subjected to an ISO 834-1 standard fire. Results show that water content has caused a thermal instability behavior on the raw earth bricks after equalization at 50% and 75% relative humidities. Thermally stable bricks displayed a noticeable diffusion of cracks on their heated face. Furthermore, cement stabili...
Permeability is related to the interconnectivity of the pores in the concrete, which measures how... more Permeability is related to the interconnectivity of the pores in the concrete, which measures how fast the gases or liquids will flow through it due to a pressure gradient. Knowledge of permeability will allow us to better understand the fluid transport behaviour in concrete, which could influence its fire spalling behaviour by directly influencing the build-up of pore pressure during heating. Three different gas permeability tests were carried out in SIAME and CSTB on 2 concretes B40-II (3% of slag) and B40-III (43% of slag). They are as follows: i) Residual axial permeability tests under radial confining pressure after unloaded preheating, ii) Residual axial permeability tests under radial confining pressure after preheating under uniaxial loading and iii) Residual radial permeability tests under uniaxial loading. The experimental test results have clearly shown that the presence of loading and their levels have a significant influence on the permeability of concrete. The permeability increase or decrease depends on the orientation and opening of cracking and these two parameters are influenced by compressive loading. The permeability of B40-III (much higher amount of slags) is more sensitive than B40-II in all heating and loading conditions
L’ecaillage des betons est un phenomene brutal pouvant etre prejudiciable pour la stabilite d'... more L’ecaillage des betons est un phenomene brutal pouvant etre prejudiciable pour la stabilite d'une structure pendant et apres un incendie. Ce phenomene depend de la composition du materiau, du chargement thermique mais aussi du changement mecanique applique. Ces dernieres annees, des etudes theoriques et experimentales ont tente d'examiner les causes possibles de l'ecaillage des betons. En particulier, de nombreuses discussions autour de l'importance relative des mecanismes thermomecaniques et thermohydriques ont ete menees. Afin de mieux comprendre l'effet du chargement mecanique sur l'ecaillage des essais feu ISO ont ete conduits sur des dalles sollicitees en compression biaxiale. Des calculs thermomecaniques (TM), reproduisant le deroulement des essais, ont ete effectues avec le code aux elements finis CAST3M. Le travail realise a permis de bien predire a la fois l'evolution des temperatures mais aussi des deplacements dans les dalles.
The paper presents the results of a study on the impact of high temperature on compressive streng... more The paper presents the results of a study on the impact of high temperature on compressive strength and ultrasonic pulse velocity in ordinary (OC) and high performance concrete (HPC). The relationship between concrete residual compressive strength (f cT) and ultrasonic pulse velocity (V T) was investigated and a regression curves f cT (V T) having the similar logarithmic character was proposed. The basic curve proposed in the standard EN 12504-4 appears to be not appropriate in describing the dependency f cT = f(V T) for heated concrete. Due to the basic curve limitation to ultrasonic pulse velocities ranging between 4.0 and 4.8 km/s, its practical implementation for heated concretes seems to be limited. In this study most of V T values even for concrete samples heated to 200 °C were below the value of 4.0 km/s. In the paper the damage extent in thermally affected concrete element was also investigated with exponential transducers using point-by-point analyses on cored samples.
ABSTRACT This paper presents the results of an experimental study carried out on an ordinary conc... more ABSTRACT This paper presents the results of an experimental study carried out on an ordinary concrete. An original equipment allowed us to carry out compression tests at high temperatures by measuring the longitudinal and radial strains of the samples. A first series of hot compression tests allowed us to determine the stress/strain curves of the material at the various temperatures as well as the evolution of compressive strength with the temperature. Short-term creep tests were carried out at various temperatures. The recovery of material was also measured. The influence of certain parameters was studied: heating rate and preheating. At last, Thermal Strain Under Load tests allowed us to calculate the Transient Thermal Strains (TTS) of the material. The influence of certain parameters on the TTS was studied: heating rate, preheating.
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