A Fundamental Study on Evaluation of Grouting Conditions in Tendon Ducts of PC Members Using Alternating Magnetic Excitation Method

In prestressed concrete (PC) structures, inadequate grouting of tendon ducts can substantially impair the durability of the structures. This study introduces a novel approach named alternating magnetic excitation method for evaluating grouting conditions in PC tendon ducts. Using a sinusoidal alternating current to activate an excitation coil, this novel approach induces vibrations in magnetic materials within concrete, generating elastic waves detectable by sensors on the surface of concrete. The study develops a robust experimental setup and procedure, optimizes noise reduction in detected signals, and explores the method's effectiveness on prestressed concrete specimens with 50 mm concrete covers. Results validate its capability to distinguish grouted and ungrouted conditions, supported by frequency response and impedance measurements confirming mechanical resonance. Experiments on lift-off distances demonstrate effectiveness of evaluation up to 100 mm lift-off distance, showing reproducibility in identifying resonance peaks across depths. This research suggests the possibility of non-destructive evaluation in prestressed concrete structures using alternating magnetic excitation method.