Salt Saturated Mass Concrete Under Chemical Attack

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Title: Salt Saturated Mass Concrete Under Chemical Attack

Author(s): L. D. Wakeley, T. S. Poole, J. J. Ernzen, and B. D. Neeley

Publication: Special Publication

Volume: 140

Issue:

Appears on pages(s): 239-268

Keywords: cement pastes; chemical attack; degradation; deterioration; durability; mass concrete; salt water; sodium chloride; strength; subsurface structures; Materials Research

Date: 9/1/1993

Abstract:
Concrete is an essential component of the seal system planned for geologic repository under development for disposal of defense-generated radioactive wastes in the U.S. Performance requirements for concrete at this facility are unique: mass-concrete seals will be placed underground in a region where all the groundwaters are rich in chloride, and some also are highly concentrated in magnesium and sulfate ions. Sodium chloride in brines presents less of a problem than do other ions. In experiments simulating the worst-case of brine composition and availability, the nature and extent of deleterious chemical reactions were determined for materials being considered for use in mass concrete for a repository. Chemical degradation of cement pastes related to this concrete included loss of calcium and precipitation of magnesium compounds, and formation of other sulfate- and chloride-bearing phases. Calcium was lost first from calcium hydroxide and then from C-S-H. Strength loss is attributed principally to loss of these phases, and not to substitution of magnesium for calcium in hydration products.