Different electrical voltage responses of cement composites under forward and backward current directions

This study investigates the effect of input current direction on the electrical voltages of ultra-high-performance concrete containing fine steel slag aggregates (UA). For the application of electrical impedance tomography based on Laplace’s equation, electrical voltage should be identical under different input current directions. However, the electrical voltages of UA differ significantly corresponding to forward and backward current directions. The percentage differences of real voltages (VRE¯) corresponding to different input current directions are between 4.57% and 76.39% under different boundary conditions such as Wenner, same-boundary, and opposite-boundary conditions. VRE¯ originates from a different internal resistance of the internal path (Rip) corresponding to the input current direction. Among the investigated boundary conditions, the Wenner boundary condition provides the lowest VRE¯ because it leads to the generation of an almost uniform current density between the two inner probes used for measuring voltages than other conditions.