Macro and nanocreep of self-consolidating concrete
Self-consolidating concrete (SCC) is a concrete that can flow under its own weight, easily filling forms with highly congested reinforcement. Due to its fresh properties, there has been growing interest in using SCC in precast and prestressed applications. These applications are known to be sensitive to time-dependent phenomena such as creep and shrinkage. Therefore, it is important to understand the creep and shrinkage behavior of SCC compared with other types of concrete. This research presents macro and nanoscale creep experiments used for a multiscale characterization of creep of SCC. Macrocreep experiments placed different SCC and normal vibrated concrete (NVC) mixes under sustained compressive and tensile stress to compare creep of SCC with NVC. Creep of SCC was compared with NVC that has similar water/binder ratio, volume of cement paste and ultimate compressive strength. Moreover, creep of SCC was compared to creep predicted using the ACI-209 and CEB-FIB MC90-99 models. Nanoscale creep experiments were performed using nanoindentation. Nanoindentations were made using both a Berkovich indenter tip and a spherical indenter tip. Creep compliance extracted at the nanoscale from cement pastes and concrete were used to compare nanomechanical properties and nanocreep of SCC and NVC. Based on the experimental observations, it was found that SCC exhibits higher creep compliance than NVC at both length scales. To account for this, changes to the existing creep models are suggested. The high creep compliance of SCC should be considered during structural design of precast and prestressed concrete as SCC might show considerable prestress losses with time as a result of creep.
Self-consolidating concrete--Creep, Vibrated concrete--Creep, Concrete--Expansion and contraction, Precast concrete, Prestressed concrete
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