Many homeowners may be tempted to use caulk or hydraulic cement to patch concrete cracks. Caulk is superficial and will allow water to continue seeping behind the patch material resulting in effervescence. Eventually, the caulk will peel off exposing an enlarged crack due to freezing and erosion. Hydraulic cement does not bond well also leading to effervescence. Eventually, the water seepage will dislodge the cement plug.
Cracks in a poured concrete foundation which are diagonal or vertical and which are generally uniform in width, are usually shrinkage cracks and should not be ongoing nor of structural significance, though they may invite water entry through the wall.