Martin Auroy - Academia.edu (original) (raw)

Papers by Martin Auroy

Corrosion intergranulaire dans l’acide nitrique des aciers inoxydables austénitiques non sensibilisés

Revue de Métallurgie, 2010

Les aciers inoxydables austenitiques non sensibilises peuvent subir dans l’acide nitrique un type... more Les aciers inoxydables austenitiques non sensibilises peuvent subir dans l’acide nitrique un type de corrosion intergranulaire (CIG) particulier. Un modele d’estimation de la duree de vie de ces materiaux dans ces milieux est propose. Il reproduit de maniere fiable les cinetiques de corrosion obtenues experimentalement.

Representativeness of accelerated carbonation testing of cement pastes

XXII nordic Concrete Research Symposium, Aug 13, 2014

Cement and Concrete Research, 2018

The consequences of accelerated carbonation at 3% CO 2 were compared with those of natural carbon... more The consequences of accelerated carbonation at 3% CO 2 were compared with those of natural carbonation (0.04%). Cement pastes (CEM I and CEM V/A) as well as the three major constitutive phases (C-S-H of different C/S ratios, portlandite and ettringite) were used and changes in the mineralogy, microstructure, water retention and cracking were investigated. The main conclusion was that accelerated carbonation at 3% CO 2 was representative of natural carbonation although it promoted the precipitation of metastable calcium carbonate (aragonite and vaterite) in place of calcite. The results also showed that the presence of aragonite and vaterite were characteristic of the carbonation of ettringite and C-S-H respectively.

Http Www Theses Fr, Oct 2, 2014

The French design of deep geological repository involves the use of cement-based materials (vault... more The French design of deep geological repository involves the use of cement-based materials (vault cell and containers). The durability assessment over the operational phase (supply 100 years) is decisive. In operating conditions, a ventilation system would maintain the CO 2 partial pressure within the disposal, subjecting concrete to drying and carbonation. The temperature (due to the waste thermal output) and drying effects on carbonation have been studied in the past. The data acquired must however be complemented. In this sense, taking into account the water transfers simultaneously to carbonation is essential. On the one hand, because carbonation is a common pathology of reinforced concrete that leads to rebar corrosion. On the other hand, because the durability of reinforced concrete structures is dependent on their water content evolution all along their service life. The assessment of water transport properties in carbonated materials, under unsaturated conditions, is an important issue for Andra in charge of the management of radioactive waste in France. Accelerated carbonation test are performed on four hardened cement pastes (CEM I, CEM III/A, CEM V/A and a Low-pH mix) at 3% CO 2 content. The water transport properties of carbonated materials are evaluated using a simplified approach, requiring the knowledge of 3 physical parameters, accessible through experimental way: (i) porosity, (ii) water vapour desorption isotherm and (iii) permeability. The results highlight mineralogical and microstructural changes induced by carbonation: hydrates decomposition and calcium carbonate precipitation (CaCO 3) according to various polymorphs. The high decalcification of C-S-H and the polymerisation of silicates chains, leading to the formation of a calcium-enriched silica gel, are found. This results in carbonation shrinkage, responsible of microcracking. On the other hand, the reduction of porosity and specific surface area are observed. The formed carbonates fill the pores, reducing the total porosity. In this sense, the higher the initial portlandite content, the higher the amount of CaCO 3 and, consequently, the more the porosity decrease. The structure of the carbonated materials is totally different from the initial state. These changes result into a significant reduction of the water content at the equilibrium and a modification of the isotherms morphology, directly related to the microstructure evolutions. The permeability is found to decrease in the case of Portland cement (CEM I), due to porosity clogging. By contrast, it was found to increase significantly for blended cements (CEM III/A, CEM V/A and Low-pH mix), this is directly attributed to the microcracking effect which is more significant compared to porosity clogging. The initial mineralogy (portlandite and C-S-H contents) therefore plays a determinant role regarding to the carbonation impact on the cementitious materials behaviour. Furthermore, the representativeness of accelerated carbonation compared to natural one was verified. The data set acquired during this work can be extended and, applied confidently under real carbonation conditions.

Impact of carbonation on water transport properties of cement-based materials

Cement-based materials would be commonly used for nuclear waste management and, particularly for ... more Cement-based materials would be commonly used for nuclear waste management and, particularly for geological disposal vaults as well as containers in France. Under service conditions, the structures would be subjected to simulta-neous drying and carbonation. Carbonation relates to the reaction between CO2 and the hydrated cement phases (mainly portlandite and C-S-H). It induces miner-alogical and microstructural changes (due to hydrates dissolution and calcium car-bonate precipitation). It results in transport properties modifications, which can have important consequences on the durability of reinforced concrete structures. Concrete durability is greatly influenced by water: water is necessary for chemical reactions to occur and significantly impacts transport. The evaluation of the un-saturated water transport properties in carbonated materials is then an important issue. That is the aim of this study. A program has been established to assess the water transport properties in carbo...

EPJ Web of Conferences, 2013

Within the context of long-lived intermediate level radioactive waste geological disposal, reinfo... more Within the context of long-lived intermediate level radioactive waste geological disposal, reinforced concrete would be used. In service life conditions, the concrete structures would be subjected to drying and carbonation. Carbonation relates to the reaction between carbon dioxide (CO 2) and the main hydrates of the cement paste (portlandite and C-S-H). Beyond the fall of the pore solution pH, indicative of steel depassivation, carbonation induces mineralogical and microstructural changes (due to portlandite and C-S-H dissolution and calcium carbonate precipitation). This results in the modification of the transport properties, which can impact the structure durability. Because concrete durability depends on water transport, this study focuses on the influence of carbonation on water transport properties. In fact, the transport properties of sound materials are known but they still remain to be assessed for carbonated ones. An experimental program has been designed to investigate the transport properties in carbonated materials. Four hardened cement pastes, differing in mineralogy, are carbonated in an accelerated carbonation device (in controlled environmental conditions) at CO 2 partial pressure of about 3%. Once fully carbonated, all the data needed to describe water transport, using a simplified approach, will be evaluated.

MRS Proceedings, 2011

ABSTRACTThe corrosion behavior of three martensitic/ferritic oxide dispersed strengthened (ODS) s... more ABSTRACTThe corrosion behavior of three martensitic/ferritic oxide dispersed strengthened (ODS) steels with different chromium contents (respectively 9, 14 and 18wt %) has been studied in hot and concentrated nitric acid. Immersion and electrochemical tests have been carried out in different experimental conditions (temperature and nitric acid concentration). In each case, the corrosion kinetics has been characterized by mass loss measurement of samples (immersion tests) and the electrochemical behavior by linear sweep voltammetry techniques. The dependency of the corrosion rate with the chromium content in the steel, the nitric acid concentration and the temperature, has been quantitatively established and qualitatively discussed.

Impact of the use of the ferritic/martensitic ODS steels cladding on the fuel reprocessing PUREX process

Journal of Nuclear Materials, 2012

ABSTRACT Some ferritic/martensitic oxide dispersed strengthened (F/M ODS) steels are presently de... more ABSTRACT Some ferritic/martensitic oxide dispersed strengthened (F/M ODS) steels are presently developed at CEA for the fuel cladding of the next generation of sodium fast nuclear reactors. The objective of this work is to study if this change of cladding could have any consequences on the spent fuel reprocessing PUREX process. During the fuel dissolution stage the cladding can actually be corroded by nitric acid. But some process specifications impose not to exceed a limit concentration of the corrosion products such as iron and chromium in the dissolution medium. For that purpose the corrosion behavior of these F/M ODS steels is studied in hot and concentrated nitric acid. The influence of some metallurgical parameters such as the chromium content, the elaboration process and the presence of the yttrium oxides is first discussed. The influence of environmental parameters such as the nitric acid concentration, the temperature and the presence of oxidizing species coming from the fuel is then analyzed. The corrosion rate is characterized by mass loss measurements and electrochemical tests. Analyses of the corroded surface are carried out by X-ray photoelectron spectroscopy.

Cement and Concrete Research, 2015

In unsaturated conditions, the durability of concrete structures is strongly dependent on the evo... more In unsaturated conditions, the durability of concrete structures is strongly dependent on the evolution of the amount of free water within concrete porosity. Reliable durability assessment of concrete structures in relation to their environment thus requires accurate unsaturated water transport description as well as reliable input data. The effect of carbonation on water transport remains poorly studied and data are lacking. It was then the purpose of this article to acquire all the data needed to describe unsaturated water transport in carbonated cementitious materials (porosity, water retention and unsaturated permeability). Four hardened pastes made with four different binders were carbonated at 3% CO 2 to ensure representativeness with natural carbonation. Beyond the modification of the water retention curve and porosity clogging, significant microcracking due to carbonation shrinkage was observed. The consequence on permeability highlighted a competition between porosity clogging and microcracking that was dependent on the initial mineralogical composition.