Influence of vibration-induced segregation on mechanical property and chloride ion permeability of concrete with variable rheological performance

Vibrating consolidation process is widely applied to field construction of cement concrete. Improper vibration can easily lead to the instability of fresh concrete and then induce performance degradation of hardened concrete. In this study, two poker vibrators with different vibrating duration were adopted for consolidating fresh concrete mixture with variable rheological performance. The variation of apparent density along casting direction was employed to evaluate the segregation state. Rebound hammer, chloride ion penetration and cement-aggregate interfacial transition zone (ITZ) microhardness were performed on selected samples at different casting depths of hardened concrete prisms. Results show that either higher amplitude or longer duration of poker vibration causes the severer segregation of fresh concrete and the plastic viscosity plays a main role in controlling vibration-induced segregation. Both mechanical performance and chloride permeability variation along casting direction tends to linearly increase with the segregation level. The severe segregation presents a worse harmful impact on the long-term durability than on the mechanical performance. Chloride ion permeability of the top concrete exponentially increased with the thicker ITZ width or the lower ITZ bonding for all vibrated concretes. (C) 2018 Elsevier Ltd. All rights reserved.