Bond behavior between reinforcement and ultra-high toughness cementitious composite in flexural members

Bonding between reinforcement and ultra-high toughness cementitious composite (UHTCC) is of great significance for reinforced UHTCC members. In this study, bond tests were carried out on short and slender UHTCC beams to simulate bond conditions in flexural members. The experimental results indicated that, differently from the brittle failure seen in concrete specimens, a ductile pull-out failure of reinforcement was obtained for all the UHTCC specimens. The descending branches of the bond-slip curves were correlated with the shear-span ratios and cover-depth to rebar-diameter ratios of specimens. The effect of shear-span ratios on bond strength for UHTCC beams was far less than that for concrete beams. Slender UHTCC beams had greater bond strength than short beams. Based on test data from different types of specimens in this study and previous studies, the effect of cover-depth to rebar-diameter ratios, bond-length to rebar-diameter ratios, and bond test methods was analyzed, and a bond strength model was proposed which includes the effect of these parameters.