Corrosion of aluminum embedded in concrete:

Pitts, Joseph W

doi:10.6028/nbs.rpt.9521

Cited by 2 publications

(1 citation statement)

References 2 publications

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“…Due to the characteristic, high-order, interference colors of CaCO3 under cross polarized light, carbonated material can be easily differentiated from uncarbonated or partially carbonated material by a color change: a buff color matrix for carbonated material and a dark gray to black matrix for largely uncarbonated material (16). Figure 2 shows representative photomicrographs of thin sections made from the various vacuum-carbonated specimens, and this difference is readily apparent.…”

Section: Microscopic Examinationmentioning

confidence: 99%

Vacuum Method for Carbonation of Cementitious Wasteforms

Venhuis

Reardon

2001

Environ. Sci. Technol.

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The application of carbonation treatment to cement-based wasteforms as a means to reduce the leachability of entrained undesirable substances, both radioactive and nonradioactive, has been the subject of much study over the past decade. Upon carbonation, hydrated cement phases release their water of hydration and are converted into carbonate minerals. The carbonation process has been shown to reduce the pore size distribution and permeability of the cementitious materials since portions of the original pore network become sites for precipitation of secondary carbonate minerals. As a result, the leachability of entrained contaminants can be markedly reduced. Current methods to carbonate cement-based wasteforms after they have cured rely on exposure to high pressure or supercritical CO2 pressures. In this study, a new low-pressure technique is presented. The method provides more complete carbonation than high-pressure techniques. The principle is to remove the water of reaction as it is produced, thereby maintaining an open pore network to facilitate the transfer of CO2 into the specimen. This is accomplished by conducting the reaction at near-vaccum pressures in the presence of a desiccant. The near-vacuum conditions lower the impedance of water transport from the carbonating specimen to the desiccant due to the large mean free path of the water vapor molecules. The technique was applied to a series of wasteform samples with entrained cationic and anionic waste components. Carbonation penetration depths of up to 11 mm were attained within 45 h of reaction for cylindrical wasteform samples prepared with OPC at a water/cement ratio of 0.60. A carbonation penetration depth of 15 mm was attained in a 6 d reaction of blended cement (OPC and 30% Class 'F' fly ash). In standardized leach tests, cationic waste constituents showed lower leachabilities from carbonated samples than from uncarbonated samples. Anionic waste constituents, however, showed greater leachabilities, and anion leachability increased with the degree of carbonation.

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Section: Microscopic Examinationmentioning

confidence: 99%

Vacuum Method for Carbonation of Cementitious Wasteforms

Venhuis

Reardon

2001

Environ. Sci. Technol.

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Corrosion of Aluminium and Zinc in Concrete at Simulated Conditions of the Repository of Low Active Waste in Sweden

Herting

Wallinder

2021

CMD

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The corrosion performance of Aluminium (Al) and zinc (Zn) is of interest in repositories for radioactive waste as the production of hydrogen gas during their anoxic corrosion may create open pathways for the transport of radioactive ions. Al and Zn rods were embedded in concrete cylinders and immersed in artificial groundwater at anaerobic conditions for 2 weeks and up to 2 years in laboratory conditions. Corrosion rates were determined to enable predictions and estimations of risks for gas evolution and the assessment of the potential impact of corrosion on the structural integrity of concrete in the final repository of low and intermediate level metal-containing waste from dismantled nuclear power plants. Samples were collected after 2, 4, 12, 26, 52 and 104 weeks. The observed corrosion rates were higher for Al compared with Zn, as expected, but both materials revealed comparatively high initial corrosion rates that decreased with time, reaching steady state after 26–52 weeks. Some of the Al containing concrete cylinders were cracked as a result of the corrosion processes after 2 years of exposure, thereby providing free passage between the embedded metal and the surrounding environment. No such effects were observed for Zn. Comparative studies were performed on non-concrete-embedded Al and Zn immersed in artificial groundwater. Observed long-term corrosion rates (1–2 years) were similar to corresponding corrosion rates in concrete. The results indicate that immersion studies in artificial groundwater can be used to estimate the long-term corrosion performance of Zn and Al in concrete.

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Corrosion of aluminum embedded in concrete:

Cited by 2 publications

References 2 publications

Vacuum Method for Carbonation of Cementitious Wasteforms

Vacuum Method for Carbonation of Cementitious Wasteforms

Corrosion of Aluminium and Zinc in Concrete at Simulated Conditions of the Repository of Low Active Waste in Sweden

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