Sunday, May 5, 2013

Investigation With Impact Echo

When investigating defects and deficiencies in concrete you need all the information you can gather.

It would be a nice benefit if you could just drill and extract core samples from every part of your element.  Pull 50-100-500 cores from every corner; a thousand would be even better.  No matter the time it would take.  Although this task would be immensely beneficial, it would be ridiculous to "swiss cheese" the member and an extremely an unlikely option anyway.  But consider this...

With Impact Echo, Tecvac, Inc. can produce a color coded grid map depicting the condition of 20,000sf of concrete, with simulated core extractions 5'o.c., in just three days.

Impact Echo Technology utilizes an extremely advanced method of non-destructive testing that will provide the necessary background data for assistance in making the right decisions to prepare an optimum repair strategy.  Here are just a few of the common applications Tecvac technicians have performed:

  • Delamination surveys of fascia tile tunnel walls
  • Sandwiched membrane integrity
  • Internal crack, void and honeycombing 
  • Surface opening crack depth measurement
  • Debonding of topping slabs
  • Slab thickness measurement
  • Injection repair quality
  • Reinforcing debonding

The DOCtertm (Defect Orientation Confirmation Tester) introduces a short duration stress pulse into the test object by technical impact on the surface.  A compression wave then travels into the object and is reflected by internal defects or external boundaries.  The wave propagates back to the surface and again into the test object by which a transient resonance condition is set up as multiple reflections occur.  This information is picked up by a transducer placed close to the impact point, processed and presented in graphic form.

This is a core sample from a bridge member surveyed in Georgia.  Just a fine little crack, seemingly unimportant from a glance.  Technicians however, were receiving information graphs of something totally different.  Repeated shots at and near the crack produced the same is what they found through a confirmation core from that location:

Just beneath the surface was severe honeycombing attributable to poor consolidation.  At the rear end of the core there is a piece of embedded form wood.   

This condition would have been totally overlooked with an observational survey and recording.  Any repair proposed would have no doubt entailed a simple injection of the crack; which would have failed in a short period and caused a re-repair.  Impact Echo finds internal defects that cause surface defects; proper analysis leads to a proper repair. 

Each of our technicians are carefully trained in the use of Impact-Echo.  I was trained at Cornell University by the inventor over 20 years ago, when there were only two of these machines in the whole of the United States.  Our technicians performed the most extensive Impact-Echo survey ever performed in Taipei, Taiwan for the Dept. of Rapid Transit Systems on their MUTA Line.

If you want to get closer to the root of the problem...Call Tecvac, Inc.  We offer short notice world-wide service to support your efforts.

Office 703 742-9186  Toll Free 800 847-9324