Fresh state properties of fiber-reinforced concretes (FRCs) were correlated to hardened state properties by quantifying fiber segregation. Rheological characteristics were evaluated using a custom-designed and built parallel-plate rheometer. Fresh state properties of concrete mixes were varied using different combinations of plasticizing agents and viscosity modifiers. Vibration was applied to the specimens and vibration times were varied to understand the effects of vibration on fiber segregation. Two sizes of steel fibers were used. Alternating current-impedance spectroscopy (AC-IS) was employed to non-destructively characterize fiber segregation in the specimens. In addition, fiber segregation was experimentally quantified using a destructive technique in which the amount of fibers in different regions is weighed. A self-compacting concrete (SCC) mix was cast to compare segregation resistance with conventional concretes (CC). Splitting tensile tests were performed to study mechanical performance of FRC specimens. The effects of the rheological characteristics on fiber segregation and, consequently, on the mechanical performance is discussed. (c) 2006 Elsevier Ltd. All rights reserved.