EXPERIMENTAL STUDY ON BOND BEHAVIOR BETWEEN PLAIN REINFORCING BARS AND CONCRETE

For evaluating the performance of existing concrete structures reinforced with plain bars, a total of six group pullout specimens with plain steel bars and two group specimens with deformed steel bars, serving as a reference, are experimentally investigated and presented in this study. The main test parameters of this investigation include embedment length, surface type of reinforcing bars and bar diameter. The results indicated that the bond stress experienced by plain steel bars is quit lower than that of the deformed bars given equal the structural characteristics and details. Increasing smooth bar diameter leads to a lower value of bond stress when the embedment lengths are constant. Differing from the bond strength of plain steel bars, which is based primarily on chemical adhesion and frictional force, the bond stress of aluminium alloy bars is mainly experienced by chemical adhesion and about 0.21-0.56MPa, which is just one-tenth of that of plain steel bars. The concrete strength yields no apparent influence on the bond strength between plain reinforcing bars and concrete. Based on the test results, a bond-slip model at the interface between concrete and plain steel bars is put forward.