DETERMINATION OF A NITRITE-BASED CORROSION-INHIBITOR IN PLASTIC AND HARDENED CONCRETE

The use of DCI(R) (W. R. Grace and Company, Cambridge, MA) corrosion inhibitor, a 30% solution of calcium nitrite, has become an established method for reducing the corrosive action of chloride on reinforcing steer in concrete. Certain regulatory agencies require monitoring the admired concrete to verify that the specified amount of corrosion inhibitor has been added. This paper discusses a field test for confirming the presence of nitrite in plastic concrete and a laboratory method for measuring the addition rate of a nitrite-based corrosion inhibitor for hardened concrete. Our experience with these methods indicates that the concrete mix design does not generally affect the extraction of the nitrite from the concrete. However, to assure an accurate estimation of the admired nitrite, where less than 85% recovery is achieved, the amount of nitrite extracted from the test sample should be compared to that of a reference concrete having the same mix design.