Chloride-induced corrosion of reinforcing steel can cause cracking and spalling in the cover concrete because the volume of the corrosion products is many times the volume of the original metal. To control this kind of corrosion, several American Concrete Institute documents suggest limiting the chloride-ion content in concrete to 0.3% by weight of cement for reinforced concrete that will not be exposed to chlorides in service but may be wet in service. However, calcium chloride is typically used at a 2% dosage rate in plastic concrete to accelerate concrete set. This dosage rate represents a total chloride-ion content of about 1% by weight of cement, which exceeds the 0.3% maximum limit.
Although chloride levels above the 0.3% limit can lead to cracks and spalls by causing reinforcement corrosion in some structures, there's disagreement on whether chloride limitations should apply to residential foundation walls. Concrete Construction asked foundation contractor Buck Bartley of The Bartley Corp., Ashton, Md., and consultant Bill Perenchio of Wiss, Janney, Elstner Associates Inc., Northbrook, Ill., for their views.