Effects of embedded steel bars upon ultrasonic testing of concrete

Abstract

Synopsis Ultrasonic testing of a reinforced concrete member by means of the Pundit apparatus is affected by the steel bars embedded in the concrete. An investigation of the effects of the reinforcement has been made, using the bar diameter and the concrete strength as the variables. It is found that the steel bar appears to act compositely with the surrounding concrete in transmitting ultrasonic pulses. The effective pulse velocity is somewhat between the pulse velocities in the two separate media, and varies with the diameter of the bar and the pulse velocity in the concrete. An empirical formula for the effective pulse velocity is proposed. On the basis of this formula and further theoretical consideration, the zone of steel influence is defined. A correction factor is derived whereby the measured pulse velocity in a concrete–steel medium is adjusted to give the pulse velocity in the plain concrete.