Detection of Delaminations in Concrete Plates Using a Laser Ablation Impact Echo Technique

Johannes F. Scherr, Jochen Kollofrath, John S. Popovics, Benjamin Bühling, Christian U. Grosse

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


This study investigates the non-destructive detection of delaminations in concrete plates using non-contact laser ablation, instead of the conventional hammer excitation, as part of the impact echo method. We performed tests on five concrete specimens of different sizes, two of which contained artificial delaminations. A range of steel ball hammers was used as reference impulse sources, the responses of which were compared with wave excitation generated by a 7 ns pulsed 1064 nm Nd:YAG laser with 150 mJ pulse energy. Signals were recorded by surface-mounted accelerometers and two contactless methods: microphones and a laser Doppler vibrometer. The laser generates frequencies across a broad range of frequencies (0 to 150 kHz) but with much less energy than the hammers' narrower frequency spectra; the laser pulse energy transferred into the specimen is 0.07 mJ, corresponding to about 0.5 ‰ of the impulse source energy. Because of this, the thick intact plates' characteristic thickness stretch resonance frequency can be reliably detected by the hammer excitations but not when using laser excitation. However, the laser can excite low-frequency flexural vibration modes over a shallow delamination at 3 cm depth. The low-frequency flexural vibration results are verified by numerical natural frequency analysis.

Original languageEnglish
Article number11
JournalJournal of Nondestructive Evaluation
Issue number1
StatePublished - Mar 2023


  • Concrete testing
  • Defect detection
  • Impact echo
  • Lamb waves
  • Non-destructive testing
  • Vibration


Dive into the research topics of 'Detection of Delaminations in Concrete Plates Using a Laser Ablation Impact Echo Technique'. Together they form a unique fingerprint.

Cite this