A novel experimental method to determine the critical chloride content in cement-based composites

Abstract

In reinforced-concrete structural members, the protective passive film on the rebar surface is broken when a critical content of chloride ions (Ccrit) is accumulated at the rebar-concrete interface by diffusing through the concrete cover. The value of Ccrit is often used for determining maintenance schedules and service life modeling of reinforced-concrete infrastructure. A novel method for accurate determination of Ccrit is proposed in this article, which addresses some of the limitations of current practice. For the development of this method, seventeen identical beam specimens, made with reinforced-Strain-Hardening Cementitious Composite (SHCC), were prepared according to the ASTM G109 procedure. The corrosion activity was monitored using various electrochemical techniques to detect the initiation of corrosion. Immediately after corrosion initiation, each specimen was sectioned to determine the chloride contents at multiple points along the rebar-SHCC interface and to observe the depths of the tiny corrosion pits on the surface of the rebars. We found a linear correlation between the chloride content and the average corrosion pit-depth and determined the Ccrit of SHCC as the y-intercept of this linear correlation.