How would you repair a crack in an exterior, cast-in-place foundation wall?
Leaking cracks in basement walls are a fairly common problem. A simple and effective method of sealing off the leak is with the use of bentonite. Bentonite is a pulverized rock which absorbs large quantities of water, and swells to 30 times its original absolute volume, forming a jelly-like mass. When even only reasonably well contained, it prevents the passage of water. In old construction, bentonite can be used in several ways to stop leaks. A thin, dry layer can be installed on the outside of the wall. Another method is to plaster the wall with a bentonite gel. Still another method, developed by one manufacturer, is to veneer the wall with quarter-inch thick corrugated cardboard sheets which are packed with bentonite. Sacked bentonite "in the dry" is used and has proven effective where other methods have failed. For more detailed information, see "Bentonite Stops Leaks in Basement Walls,"
Concrete Construction, May, 1964, p. 129. Another method, if the wall is accessible from the outside, would be the application of a membrane waterproofing. Chiseling out the crack and filling it with a sealer might also be successful.