General Info

The impact-echo method is based on monitoring the periodic arrival of reflected stress waves and is able to obtain information on the depth of the internal reflecting interface or the thickness of a solid member.

The DOCter is a versatile, portable system based on the impact-echo method, and can be used for the following applications:

  • Measure the thickness of pavements, asphalt overlays, slabs-on-ground and walls
  • Detect the presence and depth of voids and honeycombing
  • Detect voids below slabs-on-ground
  • Evaluate the quality of grout injection in post-tensioning cable ducts
  • Integrity of a membrane below an asphalt overlay protecting structural concrete
  • Delamination surveys of bridge decks, piers, cooling towers and chimneystacks
  • Detect debonding of overlays and patches
  • Detect ASR damage and freezing-and-thawing damage
  • Measure the depth of surface-opening cracks
  • Estimate early-age strength development (with proper correlation)



A short-duration stress pulse is introduced into the member by mechanical impact. This impact generated three types of stress waves that propagate away from the impact point. A surface wave (R-wave) travels along the top surface, and a P-wave and an S-wave travel into the member. In impact-echo testing, the P-wave is used to obtain information about the member.

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