Bond of Reinforcement to Revibrated Concrete

Abstract

The effects of revibration on concrete-steel bond strength are studied. Key variables are concrete slump, bar position, and the time interval between initial vibration and revibration. No 8 (25 mm) deformed reinforcing bars were used with a 2 in. (51 mm) cover and a 10 in. (254 mm) bonded length. Concrete slumps ranged from 2 3/4 to 7 1/2 in. (70 to 190 mm). Two specimen depth were used. All specimens were modified cantilever beam specimens. The experimental results show that revibration is not universally beneficial to conrete-steel bond. Revibration appears to improve bond strength for top-cast bars placed in high-slump concrete. Revibration may, however, severely damage bond strength for bars cast in well-consolidated, low-slump concrete. Revibration is almost universally detrimental to the bond strength of bottom-cast bars. Overall, revibration tends to reduce the differences in bond strength caused by differences in slump and bar position.