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Huet B.,Schlumberger | L'Hostis V.,Laboratoire dEtude du Comportement des Betons et des Argiles | Tricheux L.,EBTP SOLEN | Idrissi H.,French National Center for Scientific Research
Materials and Corrosion | Year: 2010

The increase in the rebar corrosion rate due to the concrete carbonation is the major cause of reinforced concrete degradation. The aim of this study was to investigate the corrosion behavior of mild steel rebars in simulated carbonated concrete solution. For this purpose, thermodynamic calculations, electrochemical techniques, gravimetric measurements, and surface analyses were used. Thermodynamic investigations of the nature of the interstitial solution provides an estimation of the influence of sulfate (SO2-4) and alkali (Na+, K+) content on carbonate alkalinity of the CO2/H2O open system (pCO2=0.3 mbar). In this system, calcium-silicate hydrates (C-S-H) remain thermodynamically unstable and amorphous silica controls silicate aqueous content at 100 ppm. Electrochemical results highlight a decrease in the corrosion rate with increasing carbonate alkalinity and the introduction of silicate. The introduction of sulfate at fixed carbonate alkalinity shows a dual effect: at high carbonate alkalinity, the corrosion rate is increased whereas at low carbonate alkalinity, corrosion rate is decreased.Those results are supported by surface analysis. Authors conclude that silicate and sulfate release from cement hydrates and fixation of alkali on carbonated hydrates are key parameters to estimate mild steel corrosion in carbonated concrete. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA.

L'Hostis V.,Laboratoire dEtude du Comportement des Betons et des Argiles | Amblard E.,Laboratoire dEtude du Comportement des Betons et des Argiles | Blanc C.,Laboratoire Of Reactivitedes Surfaces Et Interfaces | Miserque F.,Laboratoire Detude Of La Corrosion Aqueuse | And 2 more authors.
Corrosion Engineering Science and Technology | Year: 2011

A large experimental campaign has been developed in order to study the passivity of steel embedded in mortar. Mortar samples, containing steel pill (initially polished or precorroded), have been placed in various conditions [relative humidities of 80, 90 and 95%; solution simulating the clay rock underground water of the French candidate site of Bure at two temperatures (25 and 50°C) and in aerated and anoxic conditions]. The passive corrosion behaviour of steel has been assessed after 6 months and after 1 year for each experiment. Gravimetric measurements(average corrosion rate evaluation), X-ray photoelectron spectroscopy and Raman spectroscopy characterisations (identification of the passive film and corrosion product nature) as well as optical and electronic microscopy analyses (corrosion layer thickness and steel/mortar interface elementary analysis) have been performed. Such analyses have been also carried out after 15 days and 1 and 3 months in order to consider the first stages of passivity in mortars. The results show that average corrosion rates determinate for polished steels are typical of passive conditions (<1 μm/year) and vary from 0.4 to 5 μm/year for the precorroded pills. Moreover, iron is detected within the cementitious material, up to 5-50 mm from the metal, indicating the transport of iron species. © 2011 Institute of Materials, Minerals and Mining.

Dehoux A.,Ecole Normale Superieure de Cachan | Dehoux A.,Andra Inc | Bouchelaghem F.,Ecole Normale Superieure de Cachan | Berthaud Y.,Ecole Normale Superieure de Cachan | And 2 more authors.
Corrosion Science | Year: 2012

A micromechanical characterization had been performed on ancient artefacts corrosion products. The proposed experimental approach allies scanning electron microscopy observations, micro-indentation tests which allow the characterization of the local stiffness of elementary constituents, and finally Raman micro-spectroscopy tests which give access to the local crystallised phases of the samples. The experimental campaign contains a large series of tests, which give us the opportunity to interpret the dispersion of local stiffness measurements. © 2011 Elsevier Ltd.

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