Le Centre pour la Communication Scientifique Directe - HAL - Diderot, 2018
Institut français des sciences et technologies des transports, de l'aménagement et des réseaux-If... more Institut français des sciences et technologies des transports, de l'aménagement et des réseaux-Ifsttar 14-20 boulevard Newton-Cité Descartes-Champs-sur-Marne-77447 Marne-la-Vallée cedex 2 www.ifsttar.fr Les collections de l'Ifsttar ouvrages scientifiques Réf : OSI4 ISBN 978-2-85782-747-4
During external sulphate attack, the penetration of sulphates within the material is the rate-lim... more During external sulphate attack, the penetration of sulphates within the material is the rate-limiting step. Thus laboratory tests can last a few years before giving usable results. It is possible to shorten the response time by stimulating the penetration of sulphates. One way to achieve that is to dry the material at 60 °C then to saturate it with a sulphate solution before the test. The impact of this thermal pre-conditioning on the sulphate attack phenomenology still remains unclear. Two external sulphate attack tests have been set on two mortar cylinders each. The monitoring of the degradation process made it possible to investigate the influence of the thermal pre-conditioning. The mechanism of external sulphate attack appeared similar for the two tests. Although the mortar cylinders with thermal pre-conditioning showed stronger degradation earlier according to certain parameters (mass, volume, radius), there was no difference regarding the beginning of the expansion.
This chapter presents the methodology and results of a comprehensive experimental study about ear... more This chapter presents the methodology and results of a comprehensive experimental study about early age behavior of concrete with recycled concrete aggregates (RCA). This study includes the determination of RCA total absorption and absorption rate, the behavior of fresh concrete under standard and severe drying conditions, and the assessment of properties of hardening concrete. The RCA used in this study (provided by RECYBÉTON Project) showed high absorption rate. They reached 90% of the nominal absorption within the first 2 h, and their absorption was even faster in fresh cement paste. The monitoring of RCA water saturation in cement paste also showed a release of absorbed water when exposed to severe drying. When shifting from standard to severe drying, the increase of evaporation rate did not result in increased shrinkage to mass-loss ratios. However higher shrinkage magnitudes were reached because plastic shrinkage development was accelerated in severe drying conditions thus it could develop before setting. The air entry pressure concept was used to analyze the cracking sensitivity of fresh concrete. It was assessed on various concrete mixtures with and without RCA. A strong correlation was found between air entry pressure and negative capillary pressure at cracking time. The Free water to Binder (W f /B) ratio was found to influence directly
A new design for an embedded strain sensor is proposed in this paper. Based on Eshelby's inclusio... more A new design for an embedded strain sensor is proposed in this paper. Based on Eshelby's inclusion model, it may be used to measure the full 3D strain or stress tensor within any solid body. Currently, common embedded strain sensors are only capable of 1D measurements. The spherical shape of our sensor allows the stress or strain that would exist in the structure without the sensor to be calculated with the aid of the Eshelby theorem (in the case of elastic behavior). We used fiber Bragg gratings to measure the deformation of the sphere-other techniques are also available. Experimental testing was performed in two settings. The first test measured the performance of a polymethylmethacrylate prototype under fluid pressure load. In a second test, a steel prototype sensor was embedded in a standardized concrete specimen under axial compression, and was successfully used to measure 3D strain in real conditions.
This study deals with the potential use of treated sediments (TS) in self-consolidating concrete.... more This study deals with the potential use of treated sediments (TS) in self-consolidating concrete. The compressive strengths of mortars have shown a significant activity of TS with cement. This activity is directly related to the particle size distribution of TS, as a higher coefficient of activity was observed for finer TSpowders. Therefore, treated sediments could be used as cementitious materials. TS were incorporated in self-consolidating concrete design as a replacement of limestone filler and aggregates. The average compressive strength of sediment-based concrete specimens is comparable to that of reference concrete. However, the use of TS resulted in a decrease in slump flow due to the high internal porosity of TS. Rheological tests have been carried out on pastes to assess the loss of workability observed on mortars and concrete. An increase in yield stress and plastic viscosity has been observed for sediment-based paste with respect to that of limestone filler leading to a lower slump flow since this parameter is closely related to yield stress. The microstructural analyses of concrete have shown the positive effect of TS on hydration at the microscopic level.
Carbonation affects the performance, serviceability and safety of reinforced concrete (RC) struct... more Carbonation affects the performance, serviceability and safety of reinforced concrete (RC) structures when they are placed in environments with important CO2 concentrations. Since the kinetics of carbonation depends on parameters that could be affected by climate change (temperature, atmospheric CO2 pressure and relative humidity), this study aims at quantifying the effect of climate change on the durability of RC structures subjected to carbonation risks. This work couples a carbonation finite element model with a comprehensive reliability approach to consider the uncertainties inherent to the deterioration process. The proposed methodology is applied to the probabilistic assessment of carbonation effects for several cities in France under various climate change scenarios. It was found that climate change and local relative humidity have a significant impact on corrosion initiation risks
Les ouvrages du génie civil sont victimes de l'apparition de microfissures dans le béton au jeune... more Les ouvrages du génie civil sont victimes de l'apparition de microfissures dans le béton au jeune âge due aux phénomènes de retraits de la pâte de ciment. L'objectif de ce travail est d'étudier l'effet d'un agent compensateur de retrait, sous forme d'adjuvant, sur les déformations libres du béton. Ainsi trois axes ont été suivis : le retrait plastique, le retrait du béton durci, ainsi que l'analyse des propriétés mécaniques. Les essais sont réalisés sur deux formulations ayant deux rapports eau sur ciment (E/C) différents : 0,65 et 0,43. L'effet de l'adjuvant a été étudié en l'ajoutant au béton à hauteur de 1% en masse du liant tout en conservant les autres paramètres de composition constants. L'amplitude du retrait de dessiccation est diminuée de 57% après 7 jours de durcissement pour le béton ayant un E/C=0,65 et 31% pour le béton avec E/C=0,43 à la même échéance. A l'âge de trois mois, cette différence diminue à 33% et 25% pour les deux bétons respectivement. En effet, une légère augmentation de la porosité totale du béton a été mesurée, ainsi qu'une diminution du pourcentage de pores les plus larges de diamètre compris entre 0,13 et 1µm. Ces pores étant les premiers à perdre l'eau interne, cette modification du réseau poreux peut expliquer la diminution du retrait du béton durci.
Recent studies on the durability of concrete structures have shown the relevance to take into acc... more Recent studies on the durability of concrete structures have shown the relevance to take into account the evolution of the strength and the damage of concrete at early ages. Research works conducted at GeM Institute since many years have concerned the characterization of early age cracking. In order to achieve these works specific procedures based on the development of original devices have been proposed. This paper focuses on three of these original procedures. It concerns an application of the ring test method to the study of earlyage autogenous shrinkage in temperature-controlled conditions, a direct tensile test device for the determination of the deformation capacity of early-age concrete, and a flexural test procedure for the measurement of the crack energy of concrete at very early ages. Test results are presented and analyzed. Résumé Les récentes études sur la durabilité des ouvrages du génie civil ont montré l'importance de tenir compte de l'évolution de la résistance et de l'endommagement du béton au jeune âge. Les travaux menés au GeM depuis plusieurs années ont porté sur la caractérisation de la fissuration des matériaux cimentaires au jeune âge. Pour cela, des procédures spécifiques, nécessitant souvent le développement de dispositifs originaux, ont été élaborées. Cet article présente trois des procédures innovantes mises au point plus récemment. Elles concernent l'extension de l'essai à l'anneau pour un contrôle en température de la fissuration au jeune âge, le développement d'un banc de traction du béton jeune pour la détermination de sa capacité de déformation et la mise en oeuvre d'un protocole expérimentale pour la mesure de l'énergie de fissuration de poutre de béton jeune. Des résultats d'essais sont présentés et analysés.
Reducing the greenhouse gas emissions is essential for sustainable development particularly the c... more Reducing the greenhouse gas emissions is essential for sustainable development particularly the carbon dioxide (CO 2). The manufacturing of Portland cement is a highly energy-intensive process requiring about four Giga Joules (4GJ) of energy per tonne of finished product. The less energy intensive materials being sought are industrial by-products that are easily available, require little or no pyro-processing and have inherent or latent cementitious properties. Reducing the cement content in concrete by 40%-60% contributes to reduce CO 2 emissions. A part of the cement content can be replaced by fly ash and other supplementary materials and high range water reducing admixtures. Use of additive minerals improves pozzolanic reaction, micro-aggregate filling and concrete durability. Long term investigations have confirmed that cements containing slag and condensed silica fume impart better resistance to formation of large pores of cement clay or cement-silica fume paste systems, consequently to a decrease in the permeability. The present paper brings the past, present and expected future in the field of concrete with additive minerals using less cement. Studies have been performed on the durability of these concretes under different environmental conditions. Parameters like compressive strength, shrinkage, effects of carbonation and acid attacks have been measured.
Mechanics and Physics of Creep, Shrinkage, and Durability of Concrete, 2013
The study presented in this paper deals with the influence of the water saturation of natural agg... more The study presented in this paper deals with the influence of the water saturation of natural aggregates on shrinkage and cracking sensitivity of concrete at early age. Limestone crushed gravels were specially chosen for this study due to their high porosity. The degree of water saturation of gravels varied, from a given concrete mixture, keeping the total water content constant. Significant variations of the plastic shrinkage and early age autogenous deformations were observed. Due to the kinetics of absorption of gravels, the water content remaining in cement paste was different from the effective water content. This was confirmed by the values of mechanical properties and porosimetry. The evolutions of elastic modulus and tensile strength were experimentally assessed and used to compare the cracking sensitivity of the three studied concretes by evaluating the self generated stresses.
Le Centre pour la Communication Scientifique Directe - HAL - Diderot, 2018
Institut français des sciences et technologies des transports, de l'aménagement et des réseaux-If... more Institut français des sciences et technologies des transports, de l'aménagement et des réseaux-Ifsttar 14-20 boulevard Newton-Cité Descartes-Champs-sur-Marne-77447 Marne-la-Vallée cedex 2 www.ifsttar.fr Les collections de l'Ifsttar ouvrages scientifiques Réf : OSI4 ISBN 978-2-85782-747-4
During external sulphate attack, the penetration of sulphates within the material is the rate-lim... more During external sulphate attack, the penetration of sulphates within the material is the rate-limiting step. Thus laboratory tests can last a few years before giving usable results. It is possible to shorten the response time by stimulating the penetration of sulphates. One way to achieve that is to dry the material at 60 °C then to saturate it with a sulphate solution before the test. The impact of this thermal pre-conditioning on the sulphate attack phenomenology still remains unclear. Two external sulphate attack tests have been set on two mortar cylinders each. The monitoring of the degradation process made it possible to investigate the influence of the thermal pre-conditioning. The mechanism of external sulphate attack appeared similar for the two tests. Although the mortar cylinders with thermal pre-conditioning showed stronger degradation earlier according to certain parameters (mass, volume, radius), there was no difference regarding the beginning of the expansion.
This chapter presents the methodology and results of a comprehensive experimental study about ear... more This chapter presents the methodology and results of a comprehensive experimental study about early age behavior of concrete with recycled concrete aggregates (RCA). This study includes the determination of RCA total absorption and absorption rate, the behavior of fresh concrete under standard and severe drying conditions, and the assessment of properties of hardening concrete. The RCA used in this study (provided by RECYBÉTON Project) showed high absorption rate. They reached 90% of the nominal absorption within the first 2 h, and their absorption was even faster in fresh cement paste. The monitoring of RCA water saturation in cement paste also showed a release of absorbed water when exposed to severe drying. When shifting from standard to severe drying, the increase of evaporation rate did not result in increased shrinkage to mass-loss ratios. However higher shrinkage magnitudes were reached because plastic shrinkage development was accelerated in severe drying conditions thus it could develop before setting. The air entry pressure concept was used to analyze the cracking sensitivity of fresh concrete. It was assessed on various concrete mixtures with and without RCA. A strong correlation was found between air entry pressure and negative capillary pressure at cracking time. The Free water to Binder (W f /B) ratio was found to influence directly
A new design for an embedded strain sensor is proposed in this paper. Based on Eshelby's inclusio... more A new design for an embedded strain sensor is proposed in this paper. Based on Eshelby's inclusion model, it may be used to measure the full 3D strain or stress tensor within any solid body. Currently, common embedded strain sensors are only capable of 1D measurements. The spherical shape of our sensor allows the stress or strain that would exist in the structure without the sensor to be calculated with the aid of the Eshelby theorem (in the case of elastic behavior). We used fiber Bragg gratings to measure the deformation of the sphere-other techniques are also available. Experimental testing was performed in two settings. The first test measured the performance of a polymethylmethacrylate prototype under fluid pressure load. In a second test, a steel prototype sensor was embedded in a standardized concrete specimen under axial compression, and was successfully used to measure 3D strain in real conditions.
This study deals with the potential use of treated sediments (TS) in self-consolidating concrete.... more This study deals with the potential use of treated sediments (TS) in self-consolidating concrete. The compressive strengths of mortars have shown a significant activity of TS with cement. This activity is directly related to the particle size distribution of TS, as a higher coefficient of activity was observed for finer TSpowders. Therefore, treated sediments could be used as cementitious materials. TS were incorporated in self-consolidating concrete design as a replacement of limestone filler and aggregates. The average compressive strength of sediment-based concrete specimens is comparable to that of reference concrete. However, the use of TS resulted in a decrease in slump flow due to the high internal porosity of TS. Rheological tests have been carried out on pastes to assess the loss of workability observed on mortars and concrete. An increase in yield stress and plastic viscosity has been observed for sediment-based paste with respect to that of limestone filler leading to a lower slump flow since this parameter is closely related to yield stress. The microstructural analyses of concrete have shown the positive effect of TS on hydration at the microscopic level.
Carbonation affects the performance, serviceability and safety of reinforced concrete (RC) struct... more Carbonation affects the performance, serviceability and safety of reinforced concrete (RC) structures when they are placed in environments with important CO2 concentrations. Since the kinetics of carbonation depends on parameters that could be affected by climate change (temperature, atmospheric CO2 pressure and relative humidity), this study aims at quantifying the effect of climate change on the durability of RC structures subjected to carbonation risks. This work couples a carbonation finite element model with a comprehensive reliability approach to consider the uncertainties inherent to the deterioration process. The proposed methodology is applied to the probabilistic assessment of carbonation effects for several cities in France under various climate change scenarios. It was found that climate change and local relative humidity have a significant impact on corrosion initiation risks
Les ouvrages du génie civil sont victimes de l'apparition de microfissures dans le béton au jeune... more Les ouvrages du génie civil sont victimes de l'apparition de microfissures dans le béton au jeune âge due aux phénomènes de retraits de la pâte de ciment. L'objectif de ce travail est d'étudier l'effet d'un agent compensateur de retrait, sous forme d'adjuvant, sur les déformations libres du béton. Ainsi trois axes ont été suivis : le retrait plastique, le retrait du béton durci, ainsi que l'analyse des propriétés mécaniques. Les essais sont réalisés sur deux formulations ayant deux rapports eau sur ciment (E/C) différents : 0,65 et 0,43. L'effet de l'adjuvant a été étudié en l'ajoutant au béton à hauteur de 1% en masse du liant tout en conservant les autres paramètres de composition constants. L'amplitude du retrait de dessiccation est diminuée de 57% après 7 jours de durcissement pour le béton ayant un E/C=0,65 et 31% pour le béton avec E/C=0,43 à la même échéance. A l'âge de trois mois, cette différence diminue à 33% et 25% pour les deux bétons respectivement. En effet, une légère augmentation de la porosité totale du béton a été mesurée, ainsi qu'une diminution du pourcentage de pores les plus larges de diamètre compris entre 0,13 et 1µm. Ces pores étant les premiers à perdre l'eau interne, cette modification du réseau poreux peut expliquer la diminution du retrait du béton durci.
Recent studies on the durability of concrete structures have shown the relevance to take into acc... more Recent studies on the durability of concrete structures have shown the relevance to take into account the evolution of the strength and the damage of concrete at early ages. Research works conducted at GeM Institute since many years have concerned the characterization of early age cracking. In order to achieve these works specific procedures based on the development of original devices have been proposed. This paper focuses on three of these original procedures. It concerns an application of the ring test method to the study of earlyage autogenous shrinkage in temperature-controlled conditions, a direct tensile test device for the determination of the deformation capacity of early-age concrete, and a flexural test procedure for the measurement of the crack energy of concrete at very early ages. Test results are presented and analyzed. Résumé Les récentes études sur la durabilité des ouvrages du génie civil ont montré l'importance de tenir compte de l'évolution de la résistance et de l'endommagement du béton au jeune âge. Les travaux menés au GeM depuis plusieurs années ont porté sur la caractérisation de la fissuration des matériaux cimentaires au jeune âge. Pour cela, des procédures spécifiques, nécessitant souvent le développement de dispositifs originaux, ont été élaborées. Cet article présente trois des procédures innovantes mises au point plus récemment. Elles concernent l'extension de l'essai à l'anneau pour un contrôle en température de la fissuration au jeune âge, le développement d'un banc de traction du béton jeune pour la détermination de sa capacité de déformation et la mise en oeuvre d'un protocole expérimentale pour la mesure de l'énergie de fissuration de poutre de béton jeune. Des résultats d'essais sont présentés et analysés.
Reducing the greenhouse gas emissions is essential for sustainable development particularly the c... more Reducing the greenhouse gas emissions is essential for sustainable development particularly the carbon dioxide (CO 2). The manufacturing of Portland cement is a highly energy-intensive process requiring about four Giga Joules (4GJ) of energy per tonne of finished product. The less energy intensive materials being sought are industrial by-products that are easily available, require little or no pyro-processing and have inherent or latent cementitious properties. Reducing the cement content in concrete by 40%-60% contributes to reduce CO 2 emissions. A part of the cement content can be replaced by fly ash and other supplementary materials and high range water reducing admixtures. Use of additive minerals improves pozzolanic reaction, micro-aggregate filling and concrete durability. Long term investigations have confirmed that cements containing slag and condensed silica fume impart better resistance to formation of large pores of cement clay or cement-silica fume paste systems, consequently to a decrease in the permeability. The present paper brings the past, present and expected future in the field of concrete with additive minerals using less cement. Studies have been performed on the durability of these concretes under different environmental conditions. Parameters like compressive strength, shrinkage, effects of carbonation and acid attacks have been measured.
Mechanics and Physics of Creep, Shrinkage, and Durability of Concrete, 2013
The study presented in this paper deals with the influence of the water saturation of natural agg... more The study presented in this paper deals with the influence of the water saturation of natural aggregates on shrinkage and cracking sensitivity of concrete at early age. Limestone crushed gravels were specially chosen for this study due to their high porosity. The degree of water saturation of gravels varied, from a given concrete mixture, keeping the total water content constant. Significant variations of the plastic shrinkage and early age autogenous deformations were observed. Due to the kinetics of absorption of gravels, the water content remaining in cement paste was different from the effective water content. This was confirmed by the values of mechanical properties and porosimetry. The evolutions of elastic modulus and tensile strength were experimentally assessed and used to compare the cracking sensitivity of the three studied concretes by evaluating the self generated stresses.
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