Monitoring of concrete segregation using AC impedance spectroscopy

Segregation is one of the major phenomena decreasing the durability of concrete and increasing its risk of failure. This paper investigates the feasibility of AC Impedance Spectroscopy (ACIS) to serve as a monitoring technique for the concrete segregation during compaction. The impedances of fresh concrete were determined between compaction intervals. Changes in the calculated bulk resistivities were compared to hardened densities of the drilled cores, as well as to aggregate segregation obtained via digital image analysis of the hardened concrete sections. During the compaction process, a significant difference in the bulk resistivity was observed between the top and bottom parts of segregated specimens in comparison to unsegregated specimens. By inspecting the relationship between the measurement methods, it was found that ACIS provides a reliable approach (r=-0.948) for estimating the segregation level in cases where the resistivity is mostly affected by the movement of aggregates.