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Rebar corrosion due to carbonation in structural reinforced concretes for near-surface LLW repositories: A critical failure mechanism

Abstract

The concrete roof of a near-surface radioactive waste repository is the principle protection against water infiltration and intrusion. The following potential roof failure mechanism is examined: carbon dioxide generated by the biodegradation of organic materials in the repository initiates corrosion of reinforcing steel embedded in the concrete roof. Because the bottom surface of the roof is mostly under tension, it is susceptible to cracking. The migration path for carbon dioxide is through cracks in the concrete between the bottom of the roof and the reinforcing bars. Carbonate corrosion of the reinforcing bars may result in concrete spalling, more extensive rebar corrosion and ultimately structural failure. Attention is brought to this failure mechanism because it has generally been overlooked in repository performance assessments. Literature relevant to the above failure is reviewed. Prerequisites for rebar corrosion are the presence of carbon dioxide and oxygen in the repository gas, high relative humidity and through-cracks in the concrete. High carbon dioxide concentrations and relative humidity are expected in the repository. The oxygen concentration in the repository is expected to be very low, and that is expected to minimize rebar corrosion rates. Cracks are likely to form in locations with high tensile stresses. Healing of  More>>
Authors:
Publication Date:
Mar 01, 1995
Product Type:
Conference
Report Number:
AECL-11312; CONF-950216-
Reference Number:
SCA: 052002; 360604; PA: AIX-27:020192; EDB-96:043599; NTS-96:015304; SN: 96001551170
Resource Relation:
Conference: Waste management `95, Tucson, AZ (United States), 26 Feb - 2 Mar 1995; Other Information: PBD: Mar 1995
Subject:
05 NUCLEAR FUELS; 36 MATERIALS SCIENCE; REINFORCED CONCRETE; CORROSION; BIODEGRADATION; CARBON DIOXIDE; CONTAINMENT BUILDINGS; LOW-LEVEL RADIOACTIVE WASTES; RADIOACTIVE WASTE DISPOSAL; TENSILE PROPERTIES
OSTI ID:
189648
Research Organizations:
Atomic Energy of Canada Ltd., Chalk River, ON (Canada). Chalk River Nuclear Labs.
Country of Origin:
Canada
Language:
English
Other Identifying Numbers:
Other: ON: DE96616226; TRN: CA9500454020192
Availability:
INIS; OSTI as DE96616226
Submitting Site:
INIS
Size:
10 p.
Announcement Date:

Citation Formats

Torok, J. Rebar corrosion due to carbonation in structural reinforced concretes for near-surface LLW repositories: A critical failure mechanism. Canada: N. p., 1995. Web.
Torok, J. Rebar corrosion due to carbonation in structural reinforced concretes for near-surface LLW repositories: A critical failure mechanism. Canada.
Torok, J. 1995. "Rebar corrosion due to carbonation in structural reinforced concretes for near-surface LLW repositories: A critical failure mechanism." Canada.
@misc{etde_189648,
title = {Rebar corrosion due to carbonation in structural reinforced concretes for near-surface LLW repositories: A critical failure mechanism}
author = {Torok, J}
abstractNote = {The concrete roof of a near-surface radioactive waste repository is the principle protection against water infiltration and intrusion. The following potential roof failure mechanism is examined: carbon dioxide generated by the biodegradation of organic materials in the repository initiates corrosion of reinforcing steel embedded in the concrete roof. Because the bottom surface of the roof is mostly under tension, it is susceptible to cracking. The migration path for carbon dioxide is through cracks in the concrete between the bottom of the roof and the reinforcing bars. Carbonate corrosion of the reinforcing bars may result in concrete spalling, more extensive rebar corrosion and ultimately structural failure. Attention is brought to this failure mechanism because it has generally been overlooked in repository performance assessments. Literature relevant to the above failure is reviewed. Prerequisites for rebar corrosion are the presence of carbon dioxide and oxygen in the repository gas, high relative humidity and through-cracks in the concrete. High carbon dioxide concentrations and relative humidity are expected in the repository. The oxygen concentration in the repository is expected to be very low, and that is expected to minimize rebar corrosion rates. Cracks are likely to form in locations with high tensile stresses. Healing of the cracks could be a mitigating factor, but based on our analysis, it can not be relied on. To minimize the potential of this failure mechanism occurring with the Intrusion Resistant Underground Structure (IRUS), Canada`s proposed near-surface repository, carbon dioxide from the repository gas will be absorbed by the reactive, porous concrete placed between the waste and the roof. (author). 4 refs.}
place = {Canada}
year = {1995}
month = {Mar}
}