Page:4SIGHT manual- a computer program for modelling degradation of underground low level waste concrete vaults (IA 4sightmanualcomp5612snyd).pdf/29



To illustrate the use of, consider the following fictitious example. The concrete was designed with a 0.40 water:cement ratio. Experimental diffusivity measurements using Cl ions gave 5.0 × 10-12 m/sec. No permeability measurements are available. The roof slab is 1.0 meter thick. Regularly spaced cracks have been observed on the bottom of the slab. The cracks are approximately 100 μm wide, spaced 2 meters apart, and are assumed to extend upwards to the neutral axis which is 25 centimeters from the bottom of the roof slab. Also, the roof is buried, giving an effective pressure head of 2 meters. .

Soil analysis indicates the presence of SO at a concentration of 1.0 moles per liter. Engineering analysis indicates that if the sulfate degradation penetrates down 20 centimeters from the top surface of the roof then the vault will collapse. Additionally, chloride ions are present in the soil at a concentration of 0.40 moles per liter. and engineering drawings indicate that the reinforcement bars are located 60 centimeters from the top of the roof. Thorough soil analysis indicates that sodium ions are also present at a concentration of 2.40 moles per liter, giving a nearly neutral soil pH.

Internal to the concrete the pH is approximately 13. Therefore, internal potassium and sodium concentrations are approximately 0.1 and 0.05  moles per liter, respectively.

To monitor the ingress of the external ions, calcium and chloride  ions will be included in the output of the final state of the system. Also, to monitor leaching, the solid calcium hydroxide content will also be included in the output.

The input file for this example, is included in the distribution diskette and reiterated here: