Bond behavior of strand embedded in fiber reinforced cementitious composites

Due to the brittleness of concrete when subjected to tension, bond between prestressing strands and concrete is generally weak. Compared with conventional concrete, fiber reinforced cement composites (FRCCs) can potentially enhance bond because of the material's superior tensile behavior and ductility. The effects of FRCC materials on the bond strength and the bond stress-slip response of 0.5 in. (13 mm) seven-wire prestressing strands were investigated. Pullout tests comprising monotonic, cyclic, and reversed cyclic loads were carried out. Test results showed that the confinement effect provided by fibers after concrete cracking increased friction and mechanical interlocking between prestressing strands and the concrete matrix, leading to enhanced bond resistance (up to three times) compared with conventional concrete matrices. Unstressed strands embedded in FRCCs maintained high bond stresses up to large slip distances, resulting in a nearly elastic-perfectly plastic, bond stress-slip response. Under various types of cyclic loading, strands embedded in FRCC matrices showed ductile bond stress-slip responses with minor bond strength and stiffness degradation up to slip lengths in excess of one strand diameter, thereby dissipating a substantial amount of energy.