The performance of a 12% chromium steel in concrete in severe marine environments

Abstract

3CR12, essentially a 12% Cr steel, was used in two series of exposure programmes to assess its performance as reinforcing in concrete. In the first exposure programme, steel and 3CR12 in the pickled and passivated condition were exposed in a specially designed marine climate simulator. Comparative performance after 4 1 2 years exposure confirmed 3CR12 as a viable durable reinforcing material for concrete. In the second exposure programme, steel, 3CR12, 316 and 304 stainless steel were exposed in the hot rolled condition (scale intact). Galvanised steel and powder epoxy coated rebar were also exposed. Exposures were carried out at a severely corrosive marine site and in the simulator. Within 2 years, the results from this programme emphasized the need to remove all hot-roll scale from the 3CRI2, the 316 and 304 stainless steel rebars before being used as reinforcing in concrete. Galvanized steel rebars performed poorly. Powder epoxy coated rebars showed severe under-rusting and corrosion. By comparison steel rebars performed extremely badly. Despite the highly alkaline conditions (i.e. the absence of carbonation), chloride penetration caused severe corrosion; the chloride front penetrating through 25 mm of good concrete cover within 2 years.