Calcium chloride, the old workhorse of winter concreting, may soon be out to pasture if some have their way. In recent months the controversy over chloride limits for reinforced concrete has intensified. Views range from the one extreme a total ban on calcium chloride in reinforced concrete and in plain concrete on placed metal decks to the other extreme that it is safe to use chlorides in all concrete including prestressed concrete if the mix is properly designed and the concrete is well made. Strong feelings have developed on both sides of this issue, usually based on what appears to be convincing evidence.
Surely we need not ban all calcium chloride to solve the problem. There are circumstances in which calcium chloride can clearly be harmful and cases where there can be no harm from its use. Research shows that reinforcing steel does not rust unless moisture, oxygen and an electrolyte (to which calcium chloride can contribute) are all present in concrete at the steel surface. An adequate amount of good quality, well compacted concrete can prevent steel corrosion indefinitely in protected or dry locations. Poor quality concrete or adverse service conditions may leave steel vulnerable to corrosion which the presence of chlorides can aggravate. The problem is to distinguish among the service conditions and to set limits where they are clearly needed . . . with due consideration for both costs and benefits to come from such limitations.