Non-destructive testing methods, unlike typical destructive testing methods that deconstruct or cut the building in case of issues such as pores, heterogeneous material, cracks or any such equivalent issues inside/outside the building. And refer to the testing methods for pores, heterogeneous material, or defectiveness occurring in the specimen without changes or destruction of internal structure using ultrasound, radiation, electromagnetism, fluid, heat, or light. In this study, among such non-destructive testing methods, the impact echo method was used for an experiment to estimate the steel rebar location and thickness in the concrete mock member. The mix was made with design standard strength of 30MPa, and for the steel rebar, diameter 22mm was used on the specimen of 300×370×200 to install spacer on the ground surface, and after separating by 40mm, it was arranged with 130mm and 150mm from the top of the specimen to the top of the rebar in 1 column and 3 rows. The specimen for thickness estimation was manufactured with total length of 1800×300 and 6 varying thicknesses of 150mm, 180mm, 210mm, 240mm, 270mm, and 300mm. As the result of rebar location estimation, the maximum resonant frequency was found to be 11269Hz, 9453Hz,and the rebar location estimates were 127.8mm and 151.8mm, which was relatively accurate with error rate of 1.72% and 1.19% from the actual value. In case of thickness estimation specimen, the error rates comparing actually measured thickness and the average value were 2.2%, 2.2%, 4.6%, 0.9%, 3.8%, and 4.7%, which were relatively accurate with average of 3.1%. Through this study, the applicability of steel rebar location and thickness estimation in concrete members using impact echo method could be confirmed.
Non-destructive Testing of a 100-Year-Old Reinforced Concrete Flat Slab Bridge
