The behaviour of pre-rusted steel in concrete

This paper explores the possibility of an effective protection for precorroded steel by effect of the high alkalinity of the encasing mortar (by itself or in combination with the action of sodium nitrite). Application of a waterproof coating on the mortar surface was evaluated for this purpose. The behaviour of clean steel electrodes and in three different pre-corrosion grades was characterized from periodic measurements of the corrosion potential (Ecorr) and polarization resistance (Rp). Neither mortar alkalinity alone nor in combination with the effect of nitrite ions was found to passivate the reinforcements in the two higher corrosion grades over 2 years of exposure in an atmosphere of a high relative humidity. Also, immersion of the specimens in a 5% NaNO2 solution was found not to passivate steel undergoing active corrosion. The effectiveness of the waterproofing treatment for diminishing reinforcement corrosion was found to rely heavily on timely application.