Long-Term Performance of Engineered Concrete Barriers.
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.
