Time-to-Corrosion of Reinforcing Steel in Concrete Slabs, Volume VI: Calcium Nitrite Admixture

Abstract

Eighteen relatively large reinforced concrete slabs were fabricated in 1980 using calcium nitrite admixture with black (uncoated) steel. Their performance is compared with uncoated steel in concrete without admixtures. The slabs were placed in two lifts: the bottom lift consisted of a bottom mat of reinforcing steel in chloride-free concrete, and a top lift consisting of the top mat rebars in concrete contaminated with various quantities of sodium chloride. All the electrical connections between the reinforcing mats were made exterior to the slabs so that the corrosion current flow could be measured. After curing, the slabs were mounted above ground and exposed to the environment of the Washington, D.C., Northern Virginia area. They were periodically subjected to additional chloride exposure while being monitored for the initial 1-year period. Findings of the study indicate that the calcium nitrite can be effective in reducing rate of corrosion for black reinforcing steel embedded in salt-contaminated concrete up to a chloride/nitrite ratio of 0.9