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Evolution of pore solution chemistry, electro-osmosis

AuthorsAndrade, C.; Castellote, M.; Sarriá, J.; Alonso, C.
Issue Date20-Apr-1998
CitationMaterials and Structures
Abstract[EN]The electrochemical repair methods known as realkalisation or chloride removal, although increasingly applied, still require fundamental understanding. In the case of realkalisation, the development of an electroosmosis is claimed, which would introduce the carbonate ions into the concrete matrix; however this electroosmosis has still not been demonstrated. In the present paper, a laboratory trial is reported showing the different processes occurring throughout the experiment. In carbonated concrete, a noticeable increase in the volume of the catholyte could be identified, with the subsequent increase in the amount of carbonate, and volume decrease in the anolyte, which has been taken as an indicative of electro-osmosis. Variations of pH and the concentration of different ions have been monitored enabling the deduction that OH-, Na + are driven by the electrical field while K + and CO 3- are moved by other types of driven forces. Calculation of the potential zeta of carbonated concrete, as well as the theoretical electrical charge needed for realkalisation, is given. Finally, the corrosion rate values measured two months further after finishing the tests showed that the steel does not seem to be repassivated, although this result has to be interpreted with precaution due to the amount of oxides reduced on the steel during the treatment
[FR]Bien que les m~thodes ~lectrochimiques de r~paration de r~alcalinisation ou d'extraction des chlorures sont de plus en plus utilis&s, on ne poss~de pas de connaissances fondamentales sur les m~thodes. Darts le cas de la r&lcalinisation, une ~lectro-osmose capable d'introduire des carbonates dans la matrice du b&on se produit. Pourtant, cette ~lectro-osmose n'a pas encore pu &re d~montr&. Dans ce travail, on d~crit un essai de laboratoire qui montre les diff&ents processus qui se d&oulent pendant l'&p~rience. On a pu identifier une importante augmentation du volume du catholite et par consequent l' augmenration des carbonates et la diminution du volume de l' anolite. Ces &&ements ont ~t~ consid&& comme indicatifs d'une ~lectro-osmose. Les changements de pH et des autres ions pre'sents ont permis de dMuire que les OH- et Na + sont dirige's par le champ ~lectrique alors que K + et C03-- le sont par d'autres m&anismes. De refine, on pr&ente le calcul du potentiel zeta du b~ton carbonat~ et de la charge ~lectrique th&rique n~cessaire pour la r&Icalinisation. Finalement, la vitesse de corrosion mesur& pendant deux mois apt& la fin de l'exp&ience semble indiquer que l'acier est actif. Ce r&ultat doit ~tre interpr~t~ avec pr&aution en raison de la quantit~ d'oxydes de l'acier qui sont r~duits pendant le traitement.
Publisher version (URL)http://www.springerlink.com/content/119994/
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