Detection and Location of Defects in Externally Bonded FRP Concrete Structures-Comparison of Selected Methods

Area of Science:

• Civil Engineering
• Materials Science
• Structural Health Monitoring

Background:

• Externally bonded fiber reinforced polymer (FRP) composites are crucial for strengthening concrete structures.
• Detecting defects like delaminations and voids in these bonded structures is essential for safety and longevity.
• Nondestructive testing (NDT) methods are vital for assessing the integrity of FRP-concrete interfaces without causing damage.

Purpose of the Study:

• To compare the effectiveness of infrared thermography (IRT), ground-penetrating radar (GPR), and acoustic wave velocity (AWV) for defect detection in FRP-concrete structures.
• To evaluate the capability of these NDT methods in distinguishing overlapping defects.
• To provide insights into the advantages, limitations, and practical applications of each method.

Main Methods:

• Experimental investigation using eight concrete samples with bonded carbon fiber reinforced polymer (CFRP) strips.
• Inclusion of defect-free, single-defect (edge and center), and overlapping defect configurations.
• Application and comparison of infrared thermography, ground-penetrating radar, and acoustic wave velocity measurement techniques.

Main Results:

• Both IRT and AWV successfully detected defects (delaminations/voids) in the adhesive layer and concrete.
• GPR was unable to detect defects within the adhesive layer.
• Only IRT demonstrated the ability to differentiate between overlapping defects.

Conclusions:

• IRT and AWV are suitable for detecting general defects in FRP-concrete systems.
• IRT offers a significant advantage for identifying complex defect scenarios, including overlapping ones.
• The study provides a comparative analysis to guide the selection of appropriate NDT methods for structural health monitoring of FRP-strengthened concrete.