Analytical modelling and experimental investigation were 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 ultimately determine the feasibility of using infrared thermography to inspect substructure elements of reinforced concrete bridges. An analytical model was developed using the ANSYS finite element code. A parametric study of the influence of the various, appropriate factors was conducted. Thermal analyses consistent with diurnal temperature fluctuations and various forms of applied heating were performed. Several specimen configurations were fabricated for thermographic inspection. A number of tests were performed on a variety of concrete specimens to define the implementation parameters of the technique. The necessity of using artificial heating methods for thermal input before inspection was evaluated. The present study suggests that infrared thermography cannot be applied, in a practical manner, to substructure elements. Internal thermal gradients produced by diurnal temperature fluctuation generally are not sufficient to produce variations in surface temperature patterns necessary for detecting defects. Instead, both the envelopment and artificial heating of the substructure component are required before thermographic inspection. (Author/publisher)
Abstract