Evaluation of debonding at interface between TCL and HSB in railway concrete slabs using multi-channel IE testing

The primary objective of this research is to investigate the feasibility of multi-channel Impact-echo (IE) testing as a non-destructive evaluation method for evaluating debonding at the interface between TCL (traffic control layer) and HSB (hydraulically stabilized based course) in railway concrete slabs for the Korea train express (KTX). For these purposes, the research performed in this study includes three main tasks. First, prototype equipment was developed to perform multi-channel IE testing on the surface of concrete. Second, two concrete slab specimens (1500mm (width) × 1500mm (length) X 300mm (thickness)) were fabricated in the laboratory. Concrete slabs include six fabricated delamination defects with different areal sizes and depths. A signal interpretation method was proposed to evaluate the delamination defects using multi-channel IE testing. Third, multi-channel IE testing was applied to condition assessment of delamination defects between TCL and HSB in a real-scaled concrete mock-up specimen simulating railway concrete slabs for KTX. It was observed that the resonance frequencies measured over the delaminated defects were consistently lower than those measured in solid regions. Statistical analysis showed that the frequency difference due to delamination defects is statically meaningful at the significance level of 0.01.