Mechanical, electrical and microstructural properties of cement-based materials in conditions of current flow

Corrosion in reinforced concrete structures is not only induced by the penetration of aggressive substances (e.g. chlorides and/or CO2) but also influenced by stray currents. Further, the degradation mechanisms in reinforced cement-based systems due to the combined effect of stray current and chloride penetration have been a serious problem in civil engineering for many years. In the case when reinforced concrete is exposed to the above factors for long-term periods, service life will be reduced. With respect to the effects of stray current, the magnitude of the corrosion damage is directly related to the current density at the point of departure and the time over which the current flows. The higher the current density, the greater the resultant corrosion damage to the structure. High levels of DC stray current would dramatically decrease mechanical properties, which could be in parallel to increased chloride diffusivity and decreased threshold of chloride concentration with respect to corrosion initiation. Stray currents will therefore produce microstructural alterations, resulting from modified electrical properties of the concrete bulk matrix, which in turn will influence the corrosion resistance properties. This work reports on the influence of DC current, flowing through mortar specimens, on bulk matrix properties. The investigation presents a comparative study of mechanical properties (e.g. compressive strength), electrical resistivity and microstructure (porosity, pore size distribution) of mortar under DC current, compared to mortar in rest (no current) conditions. Additionally, numerical simulation of the stray current distribution is performed, meant to serve as a basis for further elaborated modeling of the level of current density that would exert significant microstructural alterations in a bulk cement-based matrix.Structural EngineeringCivil Engineering and Geoscience