Bond behavior of deformed steel bars in self-compacting concrete

This paper investigated the bond behavior of deformed steel bars in self-compacting concrete (SCC). Specimens with different concrete compressive strength (18.4 MPa, 27.0 MPa, and 35.6 MPa), concrete cover size (2.0 phi, 3.0 phi, 4.2 phi, and 5.0 phi), and embedded length (3.0 phi, 4.0 phi, 5.0 phi, and 6.0 phi) were prepared and tested under pull-out loading. The bond stress distribution for deformed steel bars in SCC was tentatively explored by specimens with inserted steel strain gauges. Results show that the bond strength between reinforcing bars and SCC increased with the increasing concrete grades and concrete cover depth, while specimens with lower embedded length showed higher bond strength. The larger concrete cover size and transverse reinforcements can provide effective restraint and further change the failure pattern from splitting failure to pull-out failure. The unevenness of bond stress distribution between SCC and steel bars was intensified as the embedded length increased. Compared with test results, existing empirical and code models for bond strength prediction in normal vibrated concrete were all conservative and can be extended for SCC.