A brine with a high content of calcium chloride is leaking through the concrete linings of a potash shaft and causing severe deterioration of the concrete linings. The concrete is not reinforced. How can we alleviate this problem?
The wetting and drying of surfaces of immature concrete exposed to calcium chloride solutions may cause surface scaling even in the absence of freezing temperatures. The concentration of the solution affects the severity. It was found in laboratory tests that a solution of 16 percent flake calcium chloride was highly destructive but a 2 percent solution did not cause significant scaling. Lean concrete is apparently not as susceptible as rich concrete. Concretes made with different cements (that is, types or brands) react differently for reasons not yet determined. Concrete accelerated with calcium chloride deteriorates somewhat more rapidly than comparable concrete made without it. Air entrainment was moderately effective in preventing this type of calcium chloride deterioration in laboratory tests. A period of air drying also helps prevent calcium chloride deterioration: 14 days was not sufficient; 3 months was very adequate. A linseed oil surface treatment is another method of preventing this kind of deterioration. General recommendations to prevent the problem include: Provide adequate drainage and, on flat slabs, avoid low spots. Use concrete with an adequate air content and avoid using calcium chloride accelerators or any accelerator containing calcium chloride. Provide adequate curing of the concrete and follow this with a period of air drying. After the air drying apply a linseed oil surface treatment to the concrete surface.