Theoretical approach to characterize reinforced concrete using stress waves

Although advances in nondestructive evaluation of structural concrete have been made, the ultrasonic determination of the placement of steel reinforcement in concrete remains difficult. This is not to say that the accurate determination of such characteristics is not important, however, as the deteriorating infrastructure is a serious national problem. A nondestructive method is needed that can reliably determine steel reinforcing quantity within a concrete structure. After reviewing existing methods, this paper proposes a unique approach to quantify the amount of reinforcing steel in a reinforced concrete element based on wave propagation theory and simple models. The theoretical results demonstrate that comparative L-wave velocity measurements in different directions within a reinforced concrete structure may be an excellent method to determine steel content. The applicability of surface waves for this problem is also discussed.