Geomaterials and structures team

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Laboratory for applied mechanical and electrical engineering sciences (SIAME)
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Concretes at high temperatures

People involved

Permanent:          Hélène Carré (Advisor)       
                             Christian La Borderie              
                             Olivier Nouailletas
                             Céline Perlot-Bascoulès

Temporary:    Hatem Kallel
                       Fariza Sultangaliyeva

Research focuses / scientific specificities

Characterization of concrete at high temperatures

The objective here is to determine thermal, mechanical and microstructural properties in order to develop numerical models and simulations. The difficulty lies in performing tests at high temperatures, particularly in the instrumentation.

Numerical simulations - Predicting behavior at high temperatures

Numerical simulations are performed at mesoscopic and macroscopic scales.

Assessment of concrete after a fire

After a fire, a concrete structure needs to be assessed to determine the parts to be kept and those to be demolished. To make this diagnosis easier, we are developing the use of colorimetry and the evaluation of concrete durability after heating. Currently, the condition of the concrete is often assessed based on compressive strength alone. Durability indicators must also be taken into account.

 

Partnerships

Research is conducted with different partners:

  • The CSTB: French construction industry scientific and technical center
  • The CERIB: French concrete industry study and research center
  • The IFSTTAR: French institute of science and technology for transport, development and networks
  • EDF: electricity of France
  • Universities of Bordeaux, Cergy-Pontoise, Grenoble, School of Mines of Douai...
  • Polytechnic University of Milan
  • CUT: Cracow University of Technology
  • El Manar University of Tunis
  • Etc.

Experimental means

The laboratory has various equipment for running characterization tests and small-scale fire tests.

 

Important projects/results

Here are the main projects carried out over the past few years and the key scientific results obtained:

  • Study of the risk of concrete spalling at high temperatures – CSTB project – PhD by J.C. Mindeguia
    • Demonstration of the effect of heating speed on the risk of spalling.
    • Pressure measurements at high temperatures and effect of concrete composition, heating speed, etc.
  • Study of the influence of mechanical loading on the risk of concrete spalling at high temperatures – CSTB and Polytechnic University of Milan project – PhD by Jihad Miah
    • Comparison of the effects of uniaxial and biaxial compressive loading on the risk of spalling.
    • Measurement of concrete permeability before and after heating with different types of mechanical loading.
  • Determination of the mechanical and thermal properties of concrete under controlled temperature and humidity conditions – Funding by EDF – ANR MACENA project – PhD by Hatem Kallel.
    • Development of testing device up to 140°C.
    • Demonstration of the evolution of thermal and mechanical properties under controlled temperature and humidity conditions.
  • Formulation of an ultra-fluid concrete able to resist high temperatures for the storage of nuclear waste – Funded by ANDRA – PIA UCOMP project – Partners: CERIB, CSTB, IFSTTAR
    • Determination of the effect of polypropylene fibers on the rheology of concrete.
    • Optimization of the formulation of fiber-reinforced concretes to limit the risk of spalling (in progress).

 

  Geothermics

People involved

Permanent:          Domenico Gallipoli (Advisor)
                             Christian La Borderie              

Temporary:    Agostino Walter Bruno
                             Hatem Kallel
                             Hui Wang

Research focuses / scientific specificities

The main research activities in geotechnics can be divided into four areas.

Constitutive equations for coupled hydro-mechanical modeling of three-phase porous environments

The aim of this work is to develop mathematical models that describe the behavior of geomaterials whose pores are filled partly with liquid, partly with gas, for engineering purposes. These models, which factor in the interdependence between deformation and water retention (hydro-mechanical coupling), are validated with the help of different experimental techniques:

  • Triaxial tests on partially saturated materials.
  • Observation of the wetting/drying cycle using a scanning electron microscope.
  • Mercury porosimetry and nitrogen adsorption.
  • X-ray tomography.
  • Photogrammetry analysis of high-definition images.

This research was funded by the European Commission and the Royal Society of the United Kingdom.

 

Partially saturated triaxial cells

Simulation of geotechnical problems in partially saturated soils

This work concentrates on applying the constitutive equations for coupled hydro-mechanical modeling described above to real geotechnical problems, such as the effect of rainfall on slope stability or the influence of soil heterogeneity on the behavior of foundations. Research has also been undertaken on the inverted analysis of field tests, such as manometer testing of unsaturated embankments, in order to determine the parameters of the model by combining finite element simulations and optimization algorithms. This project was funded by the European Commission and the Council for Engineering and Physical Research of the United Kingdom.

 

Landslide caused by rainfall

 

 

Evolution of the saturation of a heterogeneous embankment

 

 

 

Modeling of the porosity of a heterogeneous embankment

 

New sensors designed to monitor geotechnical structures

This activity concerns the development of new sensors (high-capacity tensiometers) to measure high capillary pressures of up to 2 MPa in partially saturated soils. The study also focuses on developing the hardware and software solutions necessary for the remote real-time monitoring of geotechnical structures using a web interface.

These sensors could also possibly be used in the agricultural industry, more particularly for smart irrigation systems which water plants depending on the level of hydric stress measured in the ground near the plants’ roots.

Work was carried out in partnership with industries in three countries (Germany, Austria and Italy) and tensiometer prototypes have been made for commercial geotechnical and agricultural applications. This research was funded by the European Commission and the British company Wykeham Farrance Ltd.

 

Sensor developed

 

Sensor developed

 

Field measurement

 

Application to the underground storage of nuclear waste

This research focuses on analyzing the technical response of geomaterials that form the natural and man-made barriers surrounding nuclear waste in the underground storage site. These geomaterials comprise the geological formation (rock) in which the storage tunnel is excavated, the fill and the swelling clay barriers placed around the waste. Studies concentrate on analyzing the mechanical response of these geomaterials to water saturation due to the water of the geological formation and the drying process induced by the exothermicity of the waste. Research is funded by the ANDRA (French national agency for the management of nuclear waste), the Scholarship Council of China and the Council for Engineering and Physical Research of the United Kingdom.

All these research themes benefit from the synergy of various skills ranging from experimental investigation to constitutive modeling to computational mechanics. This encourages the development of multi-disciplinary research with practical applications at the interface between soil mechanics, material engineering, geophysics and environmental engineering.

Partnerships

Research is conducted with different partners:

  • The European Commission
  • The Royal Society of the United Kingdom
  • The Council for Engineering and Physical Research of the United Kingdom
  • The British company Wykeham Farrance Ltd.
  • The ANDRA
  • The Scholarship Council of China
  • The LaSIE, University of La Rochelle

 

Important projects/results

NOVELIANT project

European project MAGIC (insert link to project description)

 

Eco-materials

 

People involved

Permanent:         Domenico Gallipoli
                             Hélène Carré
                             Claire Lawrence
                             Céline Perlot-Bascoulès (Advisor)

Temporary:    Walter Bruno
                             Alessia Cuccurullo
                             Hatem Kallel
                             Olivier Nouailletas
                             Sravan Muguda Viswanath

 

Research focuses / scientific specificities

Development of earth-based eco-materials

Development of a manufacturing process

The objective is to develop a process for manufacturing compressed earth blocks that has the smallest possible environmental footprint.

The end products must present the regulatory characteristics required for use in construction: their properties are therefore evaluated at the scales of the raw material, the wall and the product.

The manufacturing method developed is based on a hypercompaction procedure (up to 100 MPa). Specific molds were created.

 

Mold for manufacturing hypercompressed earth blocks

 

Stabilization and durability 

To limit the environmental impact of the products developed while improving the durability of the compressed earth bricks, stabilization methods other than hydraulic binders are being tested: mechanical, chemical, thermal, by waterproofing agents and biostabilization. To better characterize the effects the stabilization methods have on the properties, the relationship with the microstructure is determined through mercury porosimetry and nitrogen adsorption measurements and through X-ray microtomography.

The materials undergo various water-resistance tests: contact, absorption, suction, erosion, etc. Freeze-thaw-resistance is also studied.

 

Measurement of the compressive strength of compressed earth blocks.

 

Hygrothermal exchanges and indoor comfort

The hygrothermal regulation capacity of stabilized earth-based materials is evaluated through hygroscopic exchange measurements conducted on the material or the product (MBV method) and at wall scale thanks to a dual chamber with controlled temperature and humidity conditions used to simulate winter or summer conditions. Models of how earth contributes to winter or summer comfort in buildings are then developed based on these data.

The effect of incorporating plant fibers on hygrothermal behavior is currently under study.

 

Hygrothermal exchange tests performed through a wall made of compressed earth bricks

 

Measurement of hygroscopic exchanges (MBV)

 

Another area of research looks into how earth could contribute to trapping pollutants to improve indoor air quality and visual properties.

Development of eco-materials based on recycled by-products

The aim of this research project is to develop and characterize cement formulations incorporating industrial by-products (use of steel slag as an aggregate for heavy concretes, sand replaced by oyster shells, use of recycled aggregates resulting from building demolition, etc.). 

Recycling these by-products reduces the environmental footprint of the concretes developed, in particular because it helps limit the depletion of natural resources. A performance approach is applied to ensure that the cement materials developed are durable. The technical and economic aspects of the concrete manufacturing process are optimized based on lifecycle assessments.

 

Crushed oyster shells to be incorporated into concrete as an aggregate.

 

Formulation of heavy concrete incorporating steel slag for riprap.

 

Partnerships

Research is conducted with different partners:

  • The European Commission
  • The University of Durham
  • Basque Country Conurbation
  • Regional Council of Nouvelle Aquitaine
  • C2MA research center, IMT School of Mines of Alès
  • Shellfish farming union of the Bassin d’Arcachon

 

Important projects/results

European project TERRE

 

 

Durability of cement materials subject to physico-chemical stress

 

People involved

Permanent:          Christian La Borderie
                             Hélène Carré
                             Céline Perlot-Bascoulès (Advisor)   

Temporary:   Delphine Lesquerbaoults
                             Amaia Matanza Corro

 

Research focuses / scientific specificities

Evolution of properties and durability in chemically aggressive environments

This particular research aims to characterize and improve the durability of cement materials in chemically aggressive environments.

Exposure in chemically aggressive environments

To identify the parameters that govern the chemical aggressiveness of harsh environments and the phenomenology of the aggression, accelerated degradation test beds are put in place (sulfate attack, underwater carbonation, marine environment).

Mineralogical and microstructural modifications

Modifications of the mineral assemblage induced by aggressive chemical agents and their effect on the microstructure are characterized by: DRX, ATD/ATG, MEB/EDS, X-ray microtomography, mercury porosimetry and BET adsorption.

Modification of properties, evaluation and reinforcement of durability

Mechanical, transfer and interface properties are related to the state of degradation and to the microstructural modification: compressive strength, bending, crack opening, gas permeability, chloride diffusion, carbonation.

Studies are in progress to see how durability can be reinforced by biosourced nanomaterials.

These data are fed into the numerical simulations of structures’ behaviors that predict their resistance over time.

Characterization of residual durability after a fire

The microstructural modifications of the minerals and the durability indices of concretes subject to high temperatures are characterized to determine the residual durability of materials and optimize repairs of the structures.

 

Partnerships

Research is conducted with different partners:

  • The ANDRA
  • Materials Physics Center of San Sebastian, University of the Basque Country (UHV/EHU)

 

Important projects/results

ANDRA project – GL-MOUV group

Modification of mechanical and transfer properties at the interfaces of low-pH concretes induced by sulfate attacks and carbonation – ANDRA – PhD by Delphine Lesquerbault (in progress).

Nano-fiber-reinforced concretes for the durability of infrastructures in marine environments – UPV/EHU – PhD by Amaia Matanza-Corro (in progress).

DINaMO-FiVe project - Infrastructure durability in a marine environment: nanomaterials optimized by green fibers. AAP Aquitaine-Euskadi-Navarre - Partnerships with two companies – Three local authorities.

 

 

Modeling and numerical simulations

 

People involved

Permanent:          Hélène Carré
                             Domenico Gallipoli
                             Christian La Borderie (Advisor)
                             Olivier Maurel

Temporary:    Hatem Kallel
                              Hui Wang

 

Research focuses / scientific specificities

Thermal-hydro-mechanical models and structural behaviors

Nonlinear mechanical models of geomaterials (concretes and rocks) are being developed. These models can describe behaviors at mesoscopic (grain of sand) or macroscopic (homogenous material) scales. They often combine thermo-mechanical or hydro or even chemical parameters, and they are designed for use in numerical simulations to describe behaviors on a larger scale (material or structure). For example, it is possible to simulate the permeability evolution of a structure during cracking.

 

Grid at mesoscopic scale

Diffuse cracking that occurs in incipient damage manifests itself as a spreading of the total opening over several cracks which significantly changes the resulting permeability.

 

Simulation of a splitting tensile test

This effect is usually taken into account by a flow-rate coefficient, difficult to identify. Small-scale simulation makes it possible to evaluate the evolution of this coefficient.

 

Hydraulic flow-rate coefficient based on mesoscopic simulation

Models are identified drawing on lab experiments. For example, some are used to identify the tensile properties of concrete under controlled conditions of temperature and humidity.

Experimental device

Evolution of cracking energy according to temperature and humidity

 

Application to the underground storage of nuclear waste

This research focuses on analyzing the technical response of geomaterials that form the man-made barrier surrounding nuclear waste in the underground storage site. These geomaterials comprise the geological formation (rock) in which the storage tunnel is excavated, the fill and the swelling clay barriers placed around the waste. Studies concentrate on analyzing the mechanical response of these geomaterials to water saturation due to the water of the geological formation and the drying process induced by the exothermicity of the waste. Research is funded by the ANDRA (French national agency for the management of nuclear waste), the Scholarship Council of China and the Council for Engineering and Physical Research of the United Kingdom.

All these research themes benefit from the synergy of various skills ranging from experimental investigation to constitutive modeling to computational mechanics. This encourages the development of multi-disciplinary research with practical applications at the interface between soil mechanics, material engineering, geophysics and environmental engineering.

 

Evolution of stress around the excavated zone due to resaturation (left, after excavation, right, after one year).

 

Partnerships

Research is conducted with different partners:

  • The ANDRA
  • EDF
  • The CSTB

 

Important projects/results

MACENA project

PhD by Hui Wang