12 results on '"Bourbon, Xavier"'
Search Results
2. Concrete creep modelling for structural applications: non-linearity, multi-axiality, hydration, temperature and drying effects
- Author
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Sellier, Alain, Multon, Stéphane, Buffo-Lacarrière, Laurie, Vidal, Thierry, Bourbon, Xavier, Camps, Guillaume, Laboratoire Matériaux et Durabilité des constructions (LMDC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées, Agence Nationale pour la Gestion des Déchets Radioactifs (ANDRA), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)
- Subjects
modelling ,[SPI.MECA.MEMA]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Mechanics of materials [physics.class-ph] ,concrete ,[SPI.GCIV.MAT]Engineering Sciences [physics]/Civil Engineering/Matériaux composites et construction ,compression ,creep - Abstract
International audience; Concrete creep models have to consider several important phenomena (non-linearity, multi-axiality, hydration, and thermal and drying effects) to be relevant in structural applications. A selection of experimental results of creep tests found in the scientific literature are used to highlight these phenomena. Firstly, regarding the creep rate in different directions of a specimen under various loads, it is shown that creep rate under moderate loading can derive from elastic strains. Secondly, the reason why a Drucker Prager criterion can be chosen to model non-linear creep is discussed. Thirdly the interest of resorting to a creep theory able to decouple ageing (or hydration) effects and consolidation effects is explained. Moreover, interest using a poro-mechanical formulation, in which Biot coefficient depends on stress state, to model drying creep and shrinkage is discussed in the light of short meso-scopic analysis. The effect of temperature on creep is also addressed. The numerical implementation of the proposed modelling is briefly exposed and the model responses are confronted with experimental results.
- Published
- 2016
3. Orthotropic damage coupled with localized crack reclosure processing Part II: Applications
- Author
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Sellier, Alain, Casaux-Ginestet, Géraldine, Buffo-Lacarriere, Laurie, Bourbon, Xavier, Laboratoire Matériaux et Durabilité des constructions (LMDC), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA), Agence Nationale pour la Gestion des Déchets Radioactifs (ANDRA), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)
- Subjects
Reinforced concrete beam test ,[SPI.GCIV]Engineering Sciences [physics]/Civil Engineering ,Anisotropic damage ,Notched beam test ,Biaxial test ,Localization ,Split test ,Shear test ,Cyclic loading ,Crack reclosure ,Concrete - Abstract
WOS:000316092200011; International audience; This paper is concerned with the application of the orthotropic damage model described in the accompanying paper (Part I). The part I of the paper deals with several theoretical cases illustrating model's abilities to treat unilateral behaviour aspect, anisotropic loading and non radial loading pass. The second part illustrates the model's capabilities to simulate traditional laboratory tests using 3D FEM which include three points bending tests of notched beams, and examples which involve curved crack propagation, strongly anisotropic loading, and multiple cracks propagation in reinforced concrete beams. (C) 2012 Elsevier Ltd. All rights reserved.
- Published
- 2013
4. On shrinkage and structure changes of pure and blended Portland concretes.
- Author
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Zhang, Yao, Davy, Catherine A., Tricot, Gregory, Albert‐Mercier, Cyrille, Henry, Natacha, Bertier, Pieter, Cazaux, Frédéric, Damidot, Denis, and Bourbon, Xavier
- Subjects
PORTLAND cement ,CONCRETE ,HUMIDITY ,RIETVELD refinement ,PHASE transitions - Abstract
This research investigates the long-term shrinkage and Relative Mass Loss (RML) of mature Portland concretes (pure CEMI and blended CEMV/A), at temperatures of 20°C and 80°C. When placed at 80°C and at relative humidities (RH) below 50-60%, concrete shrinkage increases with very slow stabilization kinetics by several hundreds of μm/m, while RML remains of about 0.2%. The origins of this continued shrinkage, simultaneously with limited RML, are investigated through the changes in (i) the pore structure of the concretes (by Mercury Intrusion Porosimetry and nitrogen adsorption) and in (ii) their solid phases (by TGA/DTA, FTIR spectroscopy coupled to DVS, quantitative X-Ray Diffraction by Rietveld analysis, and
29 Si and27 Al MAS NMR). While the pore structure coarsens during continued shrinkage, several phase transformations occur, namely ettringite decomposition and changes in the silicate chain length of the C-A-S-H. While these structural changes are documented, their relationship with shrinkage/RML and to the pore structure is novel. [ABSTRACT FROM AUTHOR]- Published
- 2017
- Full Text
- View/download PDF
5. Durability of partially cured GFRP reinforcing bars in alkaline environments with or without sustained tensile load.
- Author
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Delaplanque, Noémie, Tharreau, Maxime, Chataigner, Sylvain, Quiertant, Marc, Benzarti, Karim, Battais, Ludwig, Rolland, Arnaud, Gaillet, Laurent, and Bourbon, Xavier
- Subjects
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CORROSION of reinforcing bars , *CONCRETE durability , *REINFORCED concrete , *REINFORCING bars , *ALKALI metal ions - Abstract
Corrosion of steel reinforcing bars (rebars) in reinforced concrete structures can be addressed by using corrosion-resistant materials like Fiber-Reinforced Polymers (FRP). However, in France, FRP rebars are primarily restricted to temporary applications due to lack of comprehensive durability data. While numerous studies have explored FRP durability in alkaline environments, understanding the combined effect of alkali ions and sustained loading remains limited. Furthermore, the impact of incomplete matrix curing on the long-term performance of FRP rebars is limited. Accordingly, this paper investigates the durability of Glass FRP (GFRP) rebars exposed to alkali environments at varying temperatures. A batch of partially cured rebars was selected for this study, with part of them undergoing post-curing to investigate the effect of curing state on the ageing behaviour. Additionally, some partially cured specimens were subjected to combined sustained tensile loading at 20 % and 40 % of ultimate strength. Mechanical, physico-chemical and microstructural characterizations were conducted after various exposure durations. Results revealed that incomplete curing minimally impacted long-term tensile properties but significantly affected the interlaminar shear strength of aged rebars. Moreover, applying a combined load had little influence on residual properties at 20°C but led to rapid reduction in GFRP residual tensile strength at higher ageing temperatures (40 and 60°C). • Incomplete curing of GFRPs did not affect residual tensile properties after 90 days of direct alkaline aging. • For partially cured GFRP rebars, both post-curing and degradation occur during aging. • Sustained load significantly impacts the durability of GFRPs in alkaline environments. • This load effect exhibits high dependence on temperature. • Partial curing of the GFRPs may amplify the effect of load on long term performance. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
6. Chloride diffusion coefficient: A comparison between impedance spectroscopy and electrokinetic tests
- Author
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Mercado, Hugo, Lorente, Sylvie, and Bourbon, Xavier
- Subjects
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CHLORIDES , *DIFFUSION , *IMPEDANCE spectroscopy , *ELECTROKINETICS , *TITANIUM dioxide , *STRENGTH of materials - Abstract
Abstract: This paper proposes to compare several experimental ways of obtaining the chloride diffusion coefficient through saturated porous materials. The first method is based on the application of the Nernst–Einstein equation for which the conductivity of the saturated sample is measured by impedance spectroscopy for two kinds of materials: inert samples of TiO2, and concretes based on type I and type V cements. The second method is a migration test in which the flux of chloride measured upstream allows calculating the diffusion coefficient by means of the Nernst–Planck equation. In the third case, the diffusion coefficient is calculated by current measurements in an equivalent configuration as the second method. It is shown that the formation factor does not vary neither with the ionic strength of the saturation solution, nor with the change in the pore solution constituents when the material is without mineral additions. The CEM-V concrete exhibits a specific behavior with a strong influence of the addition of chloride in its pore solution on the formation factor. The diffusion coefficients calculated with the three methods are in good agreement provided the metrology of the experiments is carefully controlled. [Copyright &y& Elsevier]
- Published
- 2012
- Full Text
- View/download PDF
7. Comparison of performance of concrete barriers in a clayey geological medium
- Author
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Trotignon, Laurent, Peycelon, Hugues, and Bourbon, Xavier
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CONCRETE , *CLAY soils , *RADIOACTIVE waste disposal , *CONSTRUCTION materials , *CLAY - Abstract
Abstract: Cement based materials play an important role in the design and performance of future deep radioactive waste disposals. The type of materials selected for engineered barrier systems (EBS) is an important issue: protection of waste packages against corrosion and chemical degradation may be greatly enhanced by a proper choice and dimensioning. The long-term geochemical performance of two concrete types, CEM-I (pure Portland cement) and CEM-V (blended Portland, fly ash, blast furnace slag cement) was evaluated using reactive transport simulations of the interactions between the Callovo-Oxfordian mudrock (argillite) and concrete EBS over periods up to 106 years at 25°C. Simulations have been run with cylindrical geometry using the modeling tool Hytec 3.5 (ENSMP/CIG). Diffusion of solutes in the porewater of the solid media was considered to be the dominant transport process. Different scenarios were studied, including the case of sulfate attack. Various assumptions on the transport properties of the EBS and the argillite medium have been considered and compared. The interactions between concrete, CEM-I or CEM-V, and mudrock are in both cases predicted to lead to a significant clogging in the mudrock, in the vicinity of the interface with the concrete EBS. However, the nature and extent of the EBS/mudrock interface transformations greatly differ for the two materials considered. CEM-V, due to lower diffusion coefficients, keeps longer internal high pH conditions which are favorable to the waste packages from a chemical point of view. In addition, simulations predict that CEM-V material should have a better resistance to sulfate attack than CEM-I based barriers. In the case of CEM-I, the altered clay zone has a greater extent (up to 1.3m in 400,000y) and the drop of porosity is mainly due to zeolites and reprecipitated illite, quartz and calcite. For CEM-V, the altered clay zone is much smaller (less than 0.2m in 400,000y) and secondary smectite and calcite precipitation are predicted to cause porosity reduction. [Copyright &y& Elsevier]
- Published
- 2006
- Full Text
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8. Experimental investigation of the first desorption isotherm of a high performance concrete with thin sliced samples.
- Author
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Wu, Qier, Rougelot, Thomas, Burlion, Nicolas, and Bourbon, Xavier
- Subjects
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DESORPTION , *HIGH strength concrete , *ISOTHERMAL surfaces (Thermodynamics) , *RADIOACTIVE waste repositories , *WASTE management - Abstract
The aim of present study is to determine experimentally the first desorption isotherm of a high performance concrete based on CEM I cement for long-term underground nuclear waste storage structures. Thin sliced samples are used in order to reduce the time needed to obtain the complete isotherm. To ensure the experimental representativeness, a great amount of sliced samples with thickness h = 1, 2, and 3 mm have been desaturated from two different initial saturated states till reference dry state. The analysis of size effect in kinetics mass variation for fully water-saturated samples shows that thinner samples lose mass more quickly in the first days, but the size has no clear influence on the total relative mass loss once mass stabilization is reached. An important influence of initial curing condition is observed due to the creation of new surfaces and an increase in porous connectivity. The results obtained with the present experimental technique compare well with previous works on different sample geometries. A pore network model on the basis of Kelvin–Laplace’s capillary theory is implemented and shows the existence of two main desaturation modes corresponding to capillary pores and C–S–H porosity. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
9. Water retention and gas relative permeability of two industrial concretes
- Author
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Chen, Wei, Liu, Jian, Brue, Flore, Skoczylas, Frédéric, Davy, C.A., Bourbon, Xavier, and Talandier, Jean
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PERMEABILITY , *CONCRETE , *RADIOACTIVE waste storage , *MICROSTRUCTURE , *STATISTICS , *ABSORPTION , *IMBIBITION (Chemistry) , *WATER - Abstract
Abstract: This experimental study aims at identifying the water retention properties of two industrial concretes to be used for long term underground nuclear waste storage structures. Together with water retention, gas transfer properties are identified at varying water saturation level, i.e. relative gas permeability is assessed directly as a function of water saturation level Sw. The influence of the initial de-sorption path and of the subsequent re-saturation are analysed both in terms of water retention and gas transfer properties. Also, the influence of concrete microstructure upon water retention and relative gas permeability is assessed, using porosity measurements, analysis of the BET theory from water retention properties, and MIP. Finally, a single relative gas permeability curve is proposed for each concrete, based on Van Genuchten–Mualem''s statistical model, to be used for continuous modelling approaches of concrete structures, both during drying and imbibition. [Copyright &y& Elsevier]
- Published
- 2012
- Full Text
- View/download PDF
10. Effect of temperature on the water retention properties of two high performance concretes
- Author
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Brue, Flore, Davy, Catherine A., Skoczylas, Frédéric, Burlion, Nicolas, and Bourbon, Xavier
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CONCRETE , *TEMPERATURE effect , *ATMOSPHERIC temperature , *SEPARATION (Technology) , *MATHEMATICAL models , *ETTRINGITE , *COMPARATIVE studies - Abstract
Abstract: This contribution aims at (1) determining experimentally the first desorption isotherms of two high performance concretes (based on CEM I and CEM V cements), at three different temperature levels T =20, 50 and 80°C, and (2) showing whether these may be simply described by adsorption and capillarity. Results at 20°C compare well with recently published results; in particular, an important desorption is observed at high RH (≥98%). A simple pore network model, based on Kelvin–Laplace''s capillary theory, is implemented, and shows the existence of two main de-saturation modes, one at high pore radii (capillary pores), the other for pore radii on the order of a few nanometers (C-S-H porosity), where desorption is shown to occur. A complementary drying mechanism is evidenced at 80°C, which is attributed to ettringite and/or C-S-H degradation. Finally, proper numerical fitting of all isotherm data is achieved using the well-known three-parameter BSB model. [Copyright &y& Elsevier]
- Published
- 2012
- Full Text
- View/download PDF
11. Formulating a low-alkalinity, high-resistance and low-heat concrete for radioactive waste repositories
- Author
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Cau Dit Coumes, Céline, Courtois, Simone, Nectoux, Didier, Leclercq, Stéphanie, and Bourbon, Xavier
- Subjects
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HYDROGEN-ion concentration , *NUCLEAR engineering , *RADIOACTIVE wastes , *WASTE products - Abstract
Abstract: Investigations were carried out in order to formulate and characterize low-alkalinity and low-heat cements which would be compatible with an underground waste repository environment. Several systems comprising Ordinary Portland Cement (OPC), a fast-reacting pozzolan (silica fume (SF) or metakaolin (MK)) and, in some cases, a slow-reacting product (fly ash (FA) or blastfurnace slag (BFS)) were compared. Promising results were obtained with some binary mixtures of OPC and SF, and with some ternary blends of OPC, SF and FA or BFS: pH of water in equilibrium with the fully hydrated cements dropped below 11. Dependence of the properties of standard mortars on the high contents of FA and SF in the low-pH blends was examined. Combining SF and FA seemed attractive since SF compensated for the low reactivity of FA, while FA allowed to reduce the water demand, and dimensional variations of the mortars. Finally, low-heat (ΔT <20 °C under semi-adiabatic conditions) and high strength (≈70–80 MPa) concretes were prepared from two low-pH cements: a binary blend made from 60% of OPC and 40% of SF, and a ternary blend including 37.5% OPC, 32.5% SF and 30% FA. [Copyright &y& Elsevier]
- Published
- 2006
- Full Text
- View/download PDF
12. On the origins of transient thermal deformation of concrete.
- Author
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Manzoni, Florent, Vidal, Thierry, Sellier, Alain, Bourbon, Xavier, and Camps, Guillaume
- Subjects
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COMPRESSION loads , *DIFFUSION processes , *TRANSITION temperature , *CREEP (Materials) , *POROSITY - Abstract
The conditions that lead to Transient Thermal Deformation (TTD), also called Thermal Transient Creep (TTC), of concrete subjected to various temperatures and compressive loads in sealed conditions are analysed and a model based on a two-scale porosity is proposed. In this model, water expands in the smaller pores and diffuses progressively to the capillary pores at the upper scale. It is then shown that the water overpressure in smaller pores and the duration of the diffusion process between the two scales of porosity control the TTD. It is also shown that creep or shrinkage before the temperature transition mitigates TTD. The aim is to provide a model able to predict the conditions for TTD to appear and the amplitude of the TTD under various thermo-mechanical conditions. The TTD model is implemented in an existing basic creep model, fitted and compared with different experimental results. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
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