Influence of bar position on bond between reinforcement and self-compacting concrete: interpretation using image analysis

Investigations on bond between self-compacting concrete and reinforcement steel have been carried out by means of pull-out tests for different position of bar during casting. Five positions were studied: horizontal (superior, inferior and median), vertical (loaded in casting direction or against casting direction). Results show that bond strength was highest for bars cast vertically and loaded against the casting direction and the bond strength, cast in horizontal position, decreases when the depth of concrete beneath the bar increases. The ratio between the bond resistance of bars cast vertically and horizontally was about 1.15. An interpretation, using image analysis, was proposed. In fact, we have observed a satisfying correlation between the bond strength and the difference between the percentage Of coarse aggregate above and below the bar for different positions.