EFFECT OF CHLORIDE IONS SOURCE ON CORROSION OF REINFORCED NORMAL AND HIGH PERFORMANCE CONCRETE

Abstract

The aim of this paper is to investigate the influence of chloride ions source on corrosion of steel embedded in different types of concrete. The experimental part consisted of: chloride content analysis, rapid chloride permeability test (RCPT), and linear polarization resistance (LPR). Sodium chloride was dissolved in the mixing water and added to concrete to achieve an internal chloride content of 0.8 % by weight of cement. External exposure was provided by curing the concrete specimens in 4.5 % of NaCl solution. The chloride analysis results indicated that the ratio between (Clfree/Cltotal) for high performance concrete was always less by about 76% to 82% than that of normal concrete. Exposure to external chloride increases both total and free chloride inside the concrete specimens irrespective of concrete type. Internal chloride had increased the electrical conductivity at 28-day age of the concrete by about 45% and 40% for normal and high performance concrete respectively. The corrosion current density was found to have a positive relationship with Clfree of concrete. That may be due to the influence of chloride ions on the destruction of the passive film around the steel which cause corrosion to take place and proceed. Higher measured corrosion rates are also observed in the early stage which may be related to the change of anode and cathode areas with age.

Keywords: corrosion current densityelectrical conductivityfree chloridelinear polarization measurementMetakaolinrapid chloride permeability.