Bond between Steel and Self-Consolidating Concrete: Experiments and Modeling

The proportion of mixture constituents in self-consolidating concrete (SCC) differs from that of normal vibrated concrete, which can result in a different bond performance. This paper describes an experimental investigation that was performed to study the bond between deformed bars and SCC through pullout tests on short cylindrical anchorages. The specimens were cast with plain and fiber-reinforced (1% of steel fibers) SCC to evaluate the confinement given by fibers. In the case of plain concrete, tests were performed with and without lateral pressure. To assess size effects, three bar diameters were considered, and the geometry of the specimens was adopted to assume a constant ratio between the specimen diameter/bar diameter and the bonded length/bar diameter. The results were analyzed by a limit analysis model to evaluate the ultimate bond capacity and concrete cover at which the splitting/pullout failure transition is observed. The model was consistent with experimental evidence. The bond strength of SCC was found to be higher than normal strength concrete. SCC also required a larger concrete cover than ordinary concrete to attain pullout failure. Tests also showed a significant size effect on bond strength, with the smaller bar diameter exhibiting a higher strength than the larger one. By introducing confinement, a pullout failure was detected but splitting cracks were still present. Fibers prevented brittle failure, but slightly decreased bond strength.