XXIII ICTAM, 19–24 August 2012, Beijing, China ADVANCES IN THE COMPREHENSION OF THE MECHANICAL BEHAVIOR OF STEEL CORROSION PRODUCTS. Dehoux Anita *, **a) , Berthaud Yves * & Fatiha Bouchelaghem * * UPMC Univ. Paris 06, LMT-Cachan (ENS Cachan/UMR8535/UPMC), France ** ANDRA, Agence Nationale pour la gestion des Déchets RadioActifs, 92298 Chatenay Malabry cedex, France Summary The study presented below aims to develop the actual knowledge on mechanical properties of steel’s corrosion products. This material shows a complex pattern at the microscale with various corrosion products and crack-like porosity. As a result, we have chosen to follow a coupled modelling and experimental approach at different scales. CONTEXT Accounting for the development of corrosion layers in residual lifetime calculations of reinforced concrete structures requires a good knowledge of the mechanical properties of these products. From literature, it appears that the characteri- zation of the mechanical behavior of such corrosion products still remains to be done. The stakes are high, especially in the nuclear field, as the development of these products at the interface between the reinforcing steel and the surrounding concrete cover leads to concrete cracking. In usual computational models, the corrosion expansion is modelled by a fic- titious thermal loading which can reproduce qualitatively the cracking facies of corroded reinforced concrete. However, the lack of knowledge about the kinematics of growth and mechanics of these products limits the prediction capability of such models. Consequently, our study aims to determine the mechanical properties of these products. Figure 1. Corrosion products from reinforced concrete at different scales. From left to right: High resolution image by TEM of the crystallite sizes of goethite [1], optical microscope image, corrosion sample, corroded reinforced concrete structure [2]. In figure 1, corrosion from the reinforced concrete structure is an inherently heterogeneous porous material requiring a study on different scales. Hence, our study includes test campaigns and statistical analysis at the microscale, concur- rently with homogenization calculations with simplified scheme and effective modulus calculations to obtain the elastic mechanical properties at the mesoscale. MICROSCALE STUDY We have performed microindentation tests coupled with Raman microspectrometry analysis to determined the mechanical properties of each products of the sample [3]. It turned out that the mechanical properties are not clearly distinct because of various degrees of mixing of the different products. To assist the interpretation of microindentation tests, we analysed statistically the data by Gaussian mixture models [4] for a mechanical interpretation of the microstructure heterogeneity. Figure 2. Exploitation of microindentation data by statistical mixture model. Data from the indentation test and Gaussian resulting from the mixture model. As illustrated figure 2 each indentation point give us access to a local hardness and elastic modulus. From the grid of indents, we collected a set of data. With a statistical mixture model approach, we can determine several clusters that are a) Corresponding author. E-mail: dehoux@lmt.ens-cachan.fr