An experimental investigation was conducted to develop a laboratory technique for the
nondestructive evaluation of reinforced concrete. The methodologies were developed
with the intent of eventual field implementation to determine the feasibility of utilizing
infrared thermography to inspect substructural elements of concrete bridges.
Several specimen configurations were fabricated for thermographic inspection. A number
of tests were performed on a variety of concrete specimens to determine the implementation
parameters of the technique. The necessity of utilizing artificial heating
methods for thermal input prior to inspection was evaluated.
The present study suggests that infrared thermography cannot be applied to substructural
elements of bridges in a noncontact fashion. Internal thermal gradients produced by diurnal temperature fluctuation generally are not sufficient to produce the variations
in surface temperature patterns necessary for thermographically detecting nonvisual
subsurface defects. Rather, both the envelopment and artificial heating of the substructural
element is required prior to thermographic inspection.
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