An organic corrosion-inhibiting admixture for reinforced concrete: 18 years of field experience

Long-term, well documented field experience with organic corrosion-inhibiting admixtures for reinforced concrete is scarce. The present paper contributes to closing this gap of knowledge by reporting 18 years of field performance of a proprietary inhibitor formulation based on alkanolamines (Sika FerroGard 901). Reinforced concrete elements were exposed to chloride-bearing splash water at a road in the Swiss Alps. Periodically, chloride profiles were determined and the specimens were monitored by galvanic current measurements, potential mapping, and electrical concrete resistance measurements. After 18 years, additional electrochemical measurements were undertaken on-site and selected zones of reinforcement steel were visually inspected. While in the reference concrete, corrosion initiated after approx. 8-9 years at a cover depth of 15 mm, the reinforcing steel in the concrete with inhibitor was after 18 years still essentially free from corrosion (at identical cover depth). Thus, under the conditions of the present work, the corrosion inhibitor increased the time to initiation of chloride-induced reinforcing steel corrosion by a factor of approx. 2.