Plain rebars are often used in precast concrete elements. The provisio
n of plain rebars along either side of the precast joint will strength
en its resistance and provide greater ductility. However, to fully uti
lize plain rebars as reinforcement for concrete, some aspects of their
behavior have to be determined, including bond and anchorage in concr
ete. In this paper, the bond strength of plain rebars in concrete is s
tudied. Results of pullout tests on short lengths of plain and deforme
d rebars in concrete, are presented. The effects of rebar type, rebar
diameter, embedment length, concrete strength, and loading rate on the
bond behavior are examined. It was found that (1) the bond strength o
f plain rebars was only 28.6% that of deformed rebars; (2) the slip at
failure was greater for the plain rebars than for the deformed rebars
; and (3) increasing the concrete compressive strength was able to imp
rove the bond properties.