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Odile Abraham
Odile Abraham
18:04 Jun-15-2009
NDT Post-Doctorate position

Job Location: Nantes, France
offered by LCPC

Post-Doctorate position
Duration: 12 months, from the 1st of october 2009 (+/- 1 month)
Unite technique : Division RMS . LCPC Nantes
Contrat de recherche : FUI-MAREO : MAintenance and REpair of concrete coastal
structures: risk based Optimization
Responsable local LCPC : G. VILLAIN Tel. : 33 (0) 2 40 84 57 22 E-mail : geraldine.villain@lcpc.fr
Chercheurs associes : X. DEROBERT, O. ABRAHAM, S. PALMA-LOPES
Title : Non destructive testing by ultrasonic and electromagnetic methods of repair of reinforced concrete structures: quantification of the influence of the water content

Detailed content:
For the maintenance and the monitoring of reinforced concrete structures, it is important to evaluate durability and to follow mechanical and physicochemical degradations of the concrete and the reinforcements of the structure. The project FUI-MAREO is interested more particularly in repairs by mortars and concretes (4 different materials) as well as with the surface coatings exposed to the cycles of sea tide. It aims at optimizing repairs by evaluating the performance indicators of durability of these materials, following the time evolution of the parameters characterizing the attack by chlorides and, finally, developing probabilistic models in order to evaluate the residual service life of structures before and after repair. To manage this triennial project, different teams of research laboratories, universities (in particular Nantes-St Nazaire), private companies and building owners collaborate. The present post-doctoral position is financed by this project and thus fits in. The objective of the study undertaken in the RMS department of the LCPC is to evaluate, by non destructive methods (ND), the performance indicators and parameters related to the chloride ingress in concrete (for various concretes and mortars repairs). The ND measurement method used are: on the one hand, surface wave measurements whose results are function of the material density and moduli but are biased by the water content and, on the other hand, capacitive measurements, electric and electromagnetic methods whose characteristics are expressed according to the water and the chloride contents.

The aim of the post-doctoral work will be to quantify, clarify and explain uncertainties of the various indicators of durability obtained by all the ND methods quoted above, useful to the probabilistic models. He will determine the origin of these uncertainties related to materials heterogeneity, its hydric state, the methods of measurement as well as to the useful models passing from the characteristics of propagation to the indicators. The study will stress the influence of the material water content and will be divided into two parts:

- The first one will be devoted to the analysis of a rich set of experimental data, based on methods of determination of uncertainties of measurement available in literature. The post-doctoral scholar will process the whole set of measurement results carried out on repaired test beams (with 4 various materials) exposed in tidal zone (in situ beams) and that of slabs subjected to accelerated conditions of degradation, controlled in laboratory. He will be able to study the results of the ANR-SENSO project to evaluate uncertainties related to variabilities of heterogeneous materials.

- The second will be devoted to the quantification of the influence of the water content by calibration on small-size cores (ƒÓ=70 and h=75mm). The main part is dealing with ultrasonic body waves: the post-doctoral scholar will design a measurement device, will develop the procedure and will perform measurements on 4 studied materials with various water contents. For the electromagnetic waves, he will follow an existing calibration procedure, realize and/or coordinate ND measurements in a cylindrical coaxial cell, then analyze the results. This calibration is indeed essential to be able to correct the bias due to the water content for the mechanical waves and to quantify the influence of the water content on the whole measurements carried out in situ under variable environmental conditions.

The aimed product will consist in a complete procedure to evaluate uncertainties of ND measurements in heterogeneous materials like concrete, to calibrate ultrasonic and electromagnetic measurements according to the material water content.

Post-doctoral scholar background: The applicantfs background should lie either in ultrasonic measurement techniques (in heterogeneous materials) or in a multi-technique CND approach including methods to evaluate statistical parameters and uncertainties of measurement, but preferentially experimental. The applicant has to be a doctor at the date of beginning.

Net income / month : 1851 .
Please send your curriculum vitae and a motivation letter by e-mail to geraldine.villain@lcpc.fr (copy to
odile.abraham@lcpc.fr and Xavier.derobert@lcpc.fr)


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