Most homeowners have encountered the frustrating problem of cracks in basement walls and stubborn water leaks after a heavy rain.  They usually try to fix the crack with caulk.  But this is only a superficial repair. Water will still fill the crack on the inside and cause efflorescence, which will push off the caulk.  In a year or two, the caulk will peel.

Disappointed, the homeowner will pull off the caulk, chisel out the crack in an inverted V-groove and fill it with hydraulic cement.  But hydraulic cement does not bond well to concrete and is very rigid, while the concrete continuously moves, shrinks and expands.  Efflorescence will start coming up around the rigid plug, followed by drops of water.  After a couple years, the cement plug will get loose and water will start seeping around it.

A better repair method would be to keep the rainwater out of the crack.  But excavating and repairing the foundation crack on the exterior may cost thousands of dollars and may not be permanent either.