The influence of silica fume on the corrosion resistance of steel in high performance concrete exposed to simulated sea water

This investigation examined the influence of silica fume on the corrosion behaviour of steel in high performance concrete (HPC) by comparing the behaviour of HPC concretes with and without a 10% by mass of cement addition of silica fume. Reinforced concrete prisms (500 × 100 × 100 mm) with embedded corrosion probes were loaded in three-point bending to achieve a 0.3 mm crack and exposed to simulated sea water for up to four years. Corresponding prisms without induced cracks were also studied as controls. For the HPC with silica fume, pore size distribution measurements showed that after exposure to the simulated sea water, the hydration and pozzolanic reactions near the induced crack blocked almost all continuous pores in the 0.01 to 10 m range. This affected the type and distribution of corrosion products that formed by restricting the access of chlorides and oxygen to the surface of the steel. Thus, only magnetite (Fe₃O₄) formed and was confined the space provided by the induced crack, effectively plugging the crack. In HPC without silica fume, oxygenated corrosion products such as goethite (-FeOOH) and akaganeite (-FeOOH) formed in the induced crack region. The implications of these observations on the service life of high performance concrete structures are discussed.