Evaluation of concrete barrier performance in different geochemical environments

Concrete vaults and concrete grout materials may play an important role in the long term disposal of low level radioactive, hazardous, and mixed wastes. The success of concrete barriers in isolating the wastes from the environment is dependent upon the long term changes which occur in the concrete as it weathers. Concrete degradation by each type of attack will proceed at different rates depending upon the hydrochemical environment. Thus both the general rate of degradation and the critical type of degradation will vary depending upon site location and design. The long time scales required for waste disposal require that mathematical models be used to estimate changes in barrier material properties through time. a large number of mathematical models have been proposed for use in estimation of concrete degradation rates. This paper examines predicted degradation rates for concrete vaults as a function of water chemistry. Typical water chemistries for three different locations in the United states are examined: Humid Southeast, Midwest, and Arid West. The assignment of soil chemistry to location is only a rough approximation which serves to illustrate the types of problems which may be most prevalent in these locations. Actual soil chemistry depends as much or more upon local geology as it does climate