The building management and board at the Gulf Towers of Naples has become increasingly concerned about their Gulf of Mexico facing balconies.  Their concern lies mainly with the idea that the salt water and salt air are causing deterioration in the concrete balconies and that they are unsafe.  They have talked to several engineers to determine proper methods of testing to determine how deteriorated the concrete may actually be.  If they can determine the amount of deterioration in the concrete then they can put together a repair budget and schedule correlating directly to the amount of deterioration each balcony has.  The only methods the engineers suggested was hammer sounding and chain dragging. 

The hammer sounding method involves hitting the concrete balcony with a hammer at multiple intervals and listening for hollow sounds indicating that the concrete is failing.  This becomes a problem when you realize that you can’t quantitatively analyze the amount of deterioration.  This is also a problem when you realize that many of the balconies are covered with decorative tile.  Tile will often separate partially from the concrete and create a hollow sound.  Obviously this would not be in correlation to the concrete deterioration but rather the condition of the tile on the surface.  The chain drag method is similar.  One literally drags the chain over the surface and listens for hollow sounds.  This method, along with the hammer method, has been used successfully for years but there are obvious problems with the science.

Ground Penetrating Radar uses its electromagnetic pulse to record the two way travel time and amplitude of the rebar reflections in the concrete.  The strength of the rebar directly correlates to the amplitude of the reflection.  Therefore GPR can collect thousands and thousands of rebar data points and do a comparative analysis to determine which areas of the concrete have weak rebar amplitudes and which have strong.  The idea is that the area with weak rebar reflections represents rebar that has been deteriorated or delaminated.  If the bar in that area is weak or has spawled then it is very likely that the concrete is also deteriorated.