Changes in bond strength caused by re-vibration of concrete and the vibration of reinforcement

By means of pull-out tests the effects of (1) re-vibration of partially set concrete in which reinforcement is located, (2) the application of vibration directly to the reinforcement during concrete placement and (3) the direct vibration of bars protruding from partially set concrete are studied. The results indicate that treatments (2) and (3) have little effect, and that treatment (1) may result in a decrease of about 30 per cent in the average bond stress for the horizontal reinforcement used.