Critical Chloride Content for the Corrosion of Steel Fibres in Artificial Concrete Pore Solutions

Abstract

Reinforcing steel in concrete is usually protected against corrosion due to the high pH-value of the pore solution of the concrete. When a critical chloride concentration in the concrete is exceeded at the steel surface, the passive layer is destroyed and corrosion of the steel is initiated. This critical chloride content for the corrosion of black steel is strongly dependent on the pH-value of the pore solution: the higher the concentration of OH-negative ions, the higher the critical chloride content. For steel fibers, studies have shown that they do not corrode in concrete even in the presence of high chloride contents. Therefore, it can be assumed that the critical corrosion-inducing chloride content of steel fibers in concrete is distinctly higher than that of conventional reinforcing steel. To verify this assumption, the corrosion-inducing content of steel fibers was investigated in artificial chloride-containing pore solutions at different pH values. Five types of steel fibers were investigated at 3 pH value ranges. Results show steel fibers in artificial chloride-containing pore solutions have a significant increased resistance against chloride-inducing corrosion as compared to conventional reinforcing steel for high pH values. With decreasing wire diameter, the critical chloride content increases gradually.