A Point Source-Point Receiver, Pulse-Echo Technique for Flaw
Detection in Concrete
Nicholas J. Carino, Mary Sansalone, and Nelson N. Hsu
Appears on pages(s):
concrete slabs; Green’s function; hardened concretes; impact; non-destructive
tests; ultrasonic tests.
Numerical and experimental results are presented on the use of a point source-point receiver, pulse-echo technique to locate flaws within hardened concrete. A large concrete slab was cast with known internal flaws created by embedded polyurethane foam disks ranging from 5 to 50 cm in diameter. Using steel balls dropped onto the slab surface as a point source and a conical broadband displacement transducer with a small contact area as a point receiver, the ability of the technique to locate the embedded disks was evaluated. Numerical solutions for the response of an infinite plate to rurface impact were used to help interpret experimental signal traces. Boundaries of both planar and inclined disks were determined to within a few centimeters. It was concluded that the proposed technique can be a reliable nondestructive test method for detecting flaws and discontinuities within hardened concrete. The inherent limitations of the method are also discussed.