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Disappearance of oxygen in concrete under irradiation: The role of peroxides in radiolysis
Under irradiation, the interstitial liquid in concretes is affected by radiolysis. Normally produced with H2 in alkaline medium, O2 is not observed. It is shown that the disappearance of O2 results not only from the fast reaction with the e-aq radical, which causes a negative redox potential, but also from peroxide trapping in CaO2 dot 8H2O, a highly insoluble phase whose solubility product is estimated at 2.8 x 10-11. The disequilibrium that occurs in the redox sequence dioxygen (0) <--> superoxide (-1/2) <--> peroxide (-1) is responsible for depleting most of the oxygenated species in the solution. CaO2 dot 8H2O is formed at the expense of calcium in solution, of portlandite, and of ettringite, but, being unstable, it disappears in the cement paste when H2O2 is no longer present in the medium. Consideration of the reaction between Ca(OH)2 and H2O2 in the CHEMSIMUL kinetic code, which also highlights O2 consumption, seems to describe the long-term radiolysis of concrete accurately.
Disappearance of oxygen in concrete under irradiation: The role of peroxides in radiolysis
Under irradiation, the interstitial liquid in concretes is affected by radiolysis. Normally produced with H2 in alkaline medium, O2 is not observed. It is shown that the disappearance of O2 results not only from the fast reaction with the e-aq radical, which causes a negative redox potential, but also from peroxide trapping in CaO2 dot 8H2O, a highly insoluble phase whose solubility product is estimated at 2.8 x 10-11. The disequilibrium that occurs in the redox sequence dioxygen (0) <--> superoxide (-1/2) <--> peroxide (-1) is responsible for depleting most of the oxygenated species in the solution. CaO2 dot 8H2O is formed at the expense of calcium in solution, of portlandite, and of ettringite, but, being unstable, it disappears in the cement paste when H2O2 is no longer present in the medium. Consideration of the reaction between Ca(OH)2 and H2O2 in the CHEMSIMUL kinetic code, which also highlights O2 consumption, seems to describe the long-term radiolysis of concrete accurately.
Disappearance of oxygen in concrete under irradiation: The role of peroxides in radiolysis
Bouniol, P. (author) / Aspart, A. (author)
Cement and Concrete Research ; 28 ; 1669-1681
1998
13 Seiten, 17 Quellen
Article (Journal)
English
Disappearance of Oxygen in Concrete under Irradiation: The Role of Peroxides in Radiolysis
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