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Analysis of the relation between water and resistivity isotherms in concrete / M. C. Andrade in Materials and corrosion, Vol. 62 N° 2 (Fevrier 2011) 

Public ISBD [article]  in Materials and corrosion > Vol. 62 N° 2 (Fevrier 2011) . - pp. 130–138 Titre : Analysis of the relation between water and resistivity isotherms in concrete Type de document : texte imprimé Auteurs : M. C. Andrade, Auteur ; F. Bolzoni, Auteur ; J. Fullea, Auteur Année de publication : 2011 Article en page(s) : pp. 130–138 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Concrete  Isotherms  Moisture  Resistivity Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Concrete is a porous material, that contains an alkaline solution, whose pore network enables mass transport from the exterior. The concrete as composite material is quasi an insulator when it is dry and presents relatively low resistivities, in the order of few kΩ cm when it is fully saturated. Concrete resistivity reflects the degree of saturation and is therefore a useful indicator of the risk of chemical attack and of reinforcement corrosion. The dependence of resistivity on the degree of saturation has been studied, yet this subject has still not been fully elucidated. The present paper studies the evolution of concrete drying from the end of curing in order to analyze the water and resistivity isotherms. Four concrete mixes (w/c = 0.4 and 0.7 after 3 and 7 days of curing wrapped in plastic sheets) have been prepared and submitted to conditions of isothermic water desorption in controlled atmospheres with relative humidity (RH) of 55, 65, 75, 85, 95%. Resistivity measurements were simultaneously carried out which enabled to identify for the four mixes the water content and the RH which gives resistivity values higher than 105 Ω cm. The radii of water-filled pores calculated from Kelvin's law were found to be smaller than those calculated by integrating the mercury intrusion porosimetry (MIP) accumulated intrusion curve with the water lost during conditioning at different RHs. The water content measurement that seems to be most adequate for comparison with resistivity values is the volumetric fraction. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005777/abstract [article] Analysis of the relation between water and resistivity isotherms in concrete [texte imprimé] / M. C. Andrade, Auteur ; F. Bolzoni, Auteur ; J. Fullea, Auteur . - 2011 . - pp. 130–138. Génie Mécanique Langues : Anglais (eng) in Materials and corrosion > Vol. 62 N° 2 (Fevrier 2011) . - pp. 130–138 Mots-clés : Concrete  Isotherms  Moisture  Resistivity Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Concrete is a porous material, that contains an alkaline solution, whose pore network enables mass transport from the exterior. The concrete as composite material is quasi an insulator when it is dry and presents relatively low resistivities, in the order of few kΩ cm when it is fully saturated. Concrete resistivity reflects the degree of saturation and is therefore a useful indicator of the risk of chemical attack and of reinforcement corrosion. The dependence of resistivity on the degree of saturation has been studied, yet this subject has still not been fully elucidated. The present paper studies the evolution of concrete drying from the end of curing in order to analyze the water and resistivity isotherms. Four concrete mixes (w/c = 0.4 and 0.7 after 3 and 7 days of curing wrapped in plastic sheets) have been prepared and submitted to conditions of isothermic water desorption in controlled atmospheres with relative humidity (RH) of 55, 65, 75, 85, 95%. Resistivity measurements were simultaneously carried out which enabled to identify for the four mixes the water content and the RH which gives resistivity values higher than 105 Ω cm. The radii of water-filled pores calculated from Kelvin's law were found to be smaller than those calculated by integrating the mercury intrusion porosimetry (MIP) accumulated intrusion curve with the water lost during conditioning at different RHs. The water content measurement that seems to be most adequate for comparison with resistivity values is the volumetric fraction. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005777/abstract

Organic substances as inhibitors for chloride-induced corrosion in reinforced concrete / M. Ormellese in Materials and corrosion, Vol. 62 N° 2 (Fevrier 2011) 

Public ISBD [article]  in Materials and corrosion > Vol. 62 N° 2 (Fevrier 2011) . - pp. 170–177 Titre : Organic substances as inhibitors for chloride-induced corrosion in reinforced concrete Type de document : texte imprimé Auteurs : M. Ormellese, Auteur ; F. Bolzoni, Auteur ; L. Lazzari, Auteur Année de publication : 2011 Article en page(s) : pp. 170–177 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Chloride-induced  corrosion  Concrete  Critical  chloride  threshold  Inhibitor Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Corrosion inhibitors are used to prevent chloride-induced corrosion in reinforced concrete structures. Since performance of commercial organic inhibitors is only partially satisfactory, a 7-year long research has been carried out in order to set-up a new organic inhibitive mixture, able to prevent chlorides-induced corrosion. A first screening, by means of potentiodynamic polarisation test in alkaline synthetic pore solution, was performed on 80 organic compounds, mainly primary and tertiary amines, aminoalcohols, carboxylates compounds and aminoacids, in order to select the best inhibiting substances. The nine best inhibitive organic substances were selected for long-term tests: 2 amines (dimethylethanolamine and triethylentetramine), 4 aminoacids (aspartate, asparagine, glutamate and glutamine) and 3 carboxylates compounds (tartrate, benzoate and EDTA). Potentiostatic polarisation and free corrosion tests in synthetic pore solution were performed, as well as tests in concrete exposed to accelerated chlorides penetration. Five years of tests allow estimating the efficiency of the substances in preventing chlorides-induced corrosion, in term of influence on chlorides penetration and on critical chlorides threshold. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005763/abstract [article] Organic substances as inhibitors for chloride-induced corrosion in reinforced concrete [texte imprimé] / M. Ormellese, Auteur ; F. Bolzoni, Auteur ; L. Lazzari, Auteur . - 2011 . - pp. 170–177. Génie Mécanique Langues : Anglais (eng) in Materials and corrosion > Vol. 62 N° 2 (Fevrier 2011) . - pp. 170–177 Mots-clés : Chloride-induced  corrosion  Concrete  Critical  chloride  threshold  Inhibitor Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Corrosion inhibitors are used to prevent chloride-induced corrosion in reinforced concrete structures. Since performance of commercial organic inhibitors is only partially satisfactory, a 7-year long research has been carried out in order to set-up a new organic inhibitive mixture, able to prevent chlorides-induced corrosion. A first screening, by means of potentiodynamic polarisation test in alkaline synthetic pore solution, was performed on 80 organic compounds, mainly primary and tertiary amines, aminoalcohols, carboxylates compounds and aminoacids, in order to select the best inhibiting substances. The nine best inhibitive organic substances were selected for long-term tests: 2 amines (dimethylethanolamine and triethylentetramine), 4 aminoacids (aspartate, asparagine, glutamate and glutamine) and 3 carboxylates compounds (tartrate, benzoate and EDTA). Potentiostatic polarisation and free corrosion tests in synthetic pore solution were performed, as well as tests in concrete exposed to accelerated chlorides penetration. Five years of tests allow estimating the efficiency of the substances in preventing chlorides-induced corrosion, in term of influence on chlorides penetration and on critical chlorides threshold. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005763/abstract