A waste repository for the below ground disposal of low level radioactive waste is planned at Chalk River Nuclear Laboratories. It relies greatly on the durability of concrete for the required 500 year service life. A research program to design durable concrete and predict its service life is in progress.
The degradation of the concrete depends to a large extent on the rate of ingress of corrosive agents. Penetration of chloride and sulphate ions are particularly relevant. Twenty mix formulations were developed to create various types and qualities of concrete, and to study their behaviour in different site environmental conditions. A total of 1000 concrete specimens are being exposed at 20°C and 45°C to 25 different combinations of the corrosive agents including CO2. Procedures to measure the ionic profiles and to determine the factors controlling diffusion of the ions in the various concretes have been developed. Results of selected concrete systems exposed to chloride and sulphate solutions for 1 year are presented and discussed in terms of pore structure and permeability parameters of the concrete.