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Lecieux Y.,CNRS Foton Laboratory | Schoefs F.,CNRS Foton Laboratory | Bonnet S.,CNRS Foton Laboratory | Lecieux T.,CNRS Foton Laboratory | Lopes S.P.,LUnam IFSTTAR
Nondestructive Testing and Evaluation | Year: 2015

In this work, we seek to assess and optimise the performance of an integrated chloride detection sensor based on the DC electrical resistivity measurement. We specifically seek to evaluate the detection threshold of chlorides. The main problem of the resistivity measurements in concrete is the dispersion of results mainly linked to the material heterogeneity and electrical contact limitations. To take into account the uncertainty of the measurement, we used a measurement device and sensors based on Geoelectrical Imaging methods. It gives richer information than the one delivered by conventional resistivity measurement sensors. Thus, it allows the use of statistical analysis and quality assessment methods. Before performing tests in concrete, we worked in a medium of known and homogenous resistivity in order to assess and optimise the performances of the acquisition system. Then we performed tests on concrete specimens containing different contents of chloride ions. Performance assessment of the resistivity probe is based on an analysis of receiver operating characteristic curves and the detection threshold of chlorides is calculated using the αδ method. © 2015 Taylor & Francis.


Lecieux Y.,CNRS Foton Laboratory | Schoefs F.,CNRS Foton Laboratory | Bonnet S.,CNRS Foton Laboratory | Lopes S.P.,LUnam IFSTTAR | Roche M.,CNRS Foton Laboratory
7th European Workshop on Structural Health Monitoring, EWSHM 2014 - 2nd European Conference of the Prognostics and Health Management (PHM) Society | Year: 2014

In this work, we seek to assess and optimize the performances of an integrated resistivity sensor compatible with Geoelectrical Imaging methods. In this way, we have performed tests in a controlled environment. We specifically seek to evaluate the detection threshold of chlorides by doing tests on concrete specimens containing different concentrations of these ions. Performance assessment of the resistivity probe is based on an analysis of ROC curves and the detection threshold of chlorides is calculated using the α-δ method. Copyright © Inria (2014).


Artoni R.,LUnam IFSTTAR | Santomaso A.,University of Padua
Granular Matter | Year: 2014

Wall slip is an important phenomenon for the flow of granular materials in chutes and channels. The appearance of a slip velocity at the wall critically affects wall stresses and flow profiles, and particularly the total flowrate. In this work we show, through numerical simulations and experiments, that the global slip phenomenon at a wall has peculiar features which deviate significantly from simple sliding behavior. At first we present experimental data for the vertical chute flow which highlight that wall slip depends on many operating and system variables such as flow rate, material properties, wall properties. Secondly, we resume a large campaign of numerical data performed in 2D with polygonal particles, and try to analyse the effect of material properties, contact parameters, operating variables, different flow configurations, on the slip phenomenon. The numerical campaign allowed to identify the main parameters affecting the wall slip behavior of a numerical model of granular flow, providing the ingredients for the creation of a framework for the description of wall slip. © 2013 Springer-Verlag Berlin Heidelberg.


Volpato S.,University of Padua | Artoni R.,LUnam IFSTTAR | Santomaso A.C.,University of Padua
Chemical Engineering Research and Design | Year: 2014

In this paper the results from simulations performed using a hydrodynamic model proposed by Artoni et al. [Chem. Eng. Sci. 64 (2009a) 4040-4050] have been compared with published data of an extensive experimental investigation carried out at the Tel-Tek Research Institute in Porsgrunn, Norway. The experiments collected several data and observations on the wall stresses and the flow patterns observed during discharge of a full-scale funnel flow silo with and without inserts. The comparison between simulation and experiments showed the ability of the model to capture quantitatively the main features of both the flow and of the wall stress profiles when flow corrective inserts are put in the hopper of the silo in order to convert the discharge regime to a mass flow regime. Moreover information such as the stresses on the internals, which are difficult or impossible to get experimentally, have been collected from the simulations and discussed. © 2013 The Institution of Chemical Engineers.


Gaudefroy V.,LUnam IFSTTAR | Gros A.,Ecole Centrale Nantes | Chailleux E.,LUnam IFSTTAR | Bouron S.,LUnam IFSTTAR | Laguerre L.,LUnam IFSTTAR
Revue des Composites et des Materiaux Avances | Year: 2013

Non-destructive ultrasonic technique appear as an alternative tool to assess the stiffness of bounded mixture and compacted in addition to the classical measurement of complex modulus obtained by the two points bending test. Compression wave celerity measurements at 250 kHz have been conducted on hot and cold bituminous mixtures. Experimental results show a strong influence of the manufacturing process on the wave celerity. The feasibility of ultrasonic methods for the bituminous materials characterization is strengthened by the identification of well known effects as void content and temperaturedependant behaviour. Finally complex moduli measured from wave propagation test and two points bending test respectively have been compared. © 2013 Lavoisier.

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