Accession Number:

ADA265057

Title:

Stability of Calcium Chloroaluminate and Calcium Sulfoaluminate Phases in Hydraulic-Cement Mixtures

Descriptive Note:

Final rept.

Corporate Author:

ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS STRUCTURES LAB

Personal Author(s):

Report Date:

1993-04-01

Pagination or Media Count:

22.0

Abstract:

Throughout the 1980s expansive behavior was one of the principal design criteria for grouts and concretes to be used in underground nuclear-waste repository sealing. The purpose of this requirement was to make a material that would fit tightly into the host-rock cavity that it is inducing the formation of tetracalcium aluminate trisulfate-32-hydrate Ettringite from the reaction between the calcium aluminates or anhydrous calcium sulfoaluminates in the cementitious materials and the calcium sulfates added to the system. This is known to cause expansive behavior under certain conditions Poole and Walkeley 1992. Another design criterion has been that mixtures cannot cause dissolution of the host rock. this is not normally a problem with most host rocks, but can be a substantial problem when placing concrete in rock composed of water-soluble minerals. In the case of rocks composed of halite NACL, this problem has been solved by saturating the mixing water with sodium chloride. As a result, teracalcium aluminate dichloride-10 hydrate Chloroaluminate forms from the calcium aluminates in the cementious materials. This phase is mildly expansive. So, in hydrated systems, at least two forms of hydrated calcium aluminates may coexists, or one may form preferentially, or one may replace the other, depending on the chemical environment.

Subject Categories:

  • Adhesives, Seals and Binders
  • Civil Engineering

Distribution Statement:

APPROVED FOR PUBLIC RELEASE