We have a problem with a basement floor which we placed about a year ago. In one corner of the floor an area of concrete approximately 10 feet by 10 feet stays constantly moist. There is no moisture condition on the foundation walls whatsoever, and we do not believe that there is any spring under the floor. It has been suggested to us that possibly an excessive amount of calcium chloride gathered in this one spot and that this is the reasons for the condition. Could this be possible? If so, is there a neutralizing chemical or what can we do?
It would hardly seem that the moist spot could result from a collection of an excessive amount of calcium chloride. If this were the case, then the condition could be relieved by washing the floor with water since calcium chloride is readily soluble. The moisture has to come either from the air or from a source under the slab. Condensation occasionally takes place on concrete floors when warm, moist air comes in contact with a cool floor slab. It seems more likely that there is free water in the subgrade under this slab. This condition can be detected by drying the floor for a day or so with a fan and then securely taping a 3- to 5-foot square piece of polyethylene to the floor. This will prevent entrance of water from the air, and if the water is coming up through the slab it will collect under the polyethylene and the remedy will probably be to provide proper drainage.