Investigation of concrete mix variations and environmental conditions on defect detection ability using GPR

• Evaluation of the GPR accuracy and repeatability to detect bridge deck defects.
• We built 16 specimens, eight of them with simulated bridge deck defects.
• We found that GPR can detect defects with a radius-to-depth ratio (R/d) as small as 0.15.
• Also, GPR cannot detect cracks with 0.5 cm width placed between steel meshes.
• GPR cannot produce clear images of lightweight concrete before 3 months.

This paper presents an experimental investigation to evaluate the effects of mix variations, changes in temperature, and concrete maturity on defect detection ability using Ground Penetrating Radar (GPR) technique. Sixteen concrete specimens were prepared, eight of them with simulated bridge deck defects. Concrete type, defect type, size, and location were the parameters considered in the evaluation. Most defects were detectable by GPR under different environmental conditions in the different mixes. It was observed that defects with radius-to-depth ratio (R/d) as small as 0.15 can be detected. In all mixes, the detectable defects were visible at early and late concrete age. However, in lightweight concrete mix, defects were not detectable until 3 months after casting concrete.