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Long-Term Performance of Engineered Concrete Barriers.


pdf icon Long-Term Performance of Engineered Concrete Barriers. (1075 K)
Clifton, J. R.; Pommersheim, J. M.; Snyder, K. A.

NISTIR 5690; 19 p. July 1995.

Available from:

National Technical Information Service (NTIS), Technology Administration, U.S. Department of Commerce, Springfield, VA 22161.
Telephone: 1-800-553-6847 or 703-605-6000;
Fax: 703-605-6900.
Website: http://www.ntis.gov
Order number: PB95-260816

Keywords:

concretes; corrosion; leaching; low level nuclear disposal; modeling; service life; sulfate attack; cracking (fracturing); degradation; deterioration

Abstract:

This paper describes research being carried out at NIST on the long-term performance of concrete for constructing low-level nuclear waste (LLW) disposal facilities. These studies have included identification of likely major degradation and cracking processes, evaluation and development of accelerated degradation test methods, and the analysis and development of mathematical models for service life predictions. The major degradation processes that underground concrete will likely to encounter are sulfate attack, corrosion of reinforcing steel, alkali-aggregate reactions, and leaching by ground water. Major cracking processes in immature concrete, such as plastic shrinkage, plastic settlement, and early thermal expansion/contraction should occur before the vault is covered. Cracks caused by drying shrinkage, thermal and moisture expansion/contraction are less likely to occur once a vault is covered. Load-induced can be avoided by proper design and construction practices. Degradation processes which would likely be active above ground, but not below ground, or to be significantly more severe above ground, include freezing and thawing, drying shrinkage, cracking due to thermal and moisture expansion/contraction of concrete, abrasion by wind driven particulate matter, and impact by wind driven objects. Three major research needs have been identified which are: validation of service life models; development of performance criteria for materials and systems to repair concrete before closure of concrete vaults; and development of an expert system to dissiminate knowledge on concrete durability for constructing concrete vaults.