GPR vs Ultrasonic
GPR vs Ultrasonic
(OP)
We have a case where some new, large columns were constructed of CIP concrete and there are some surface voids after the form work was removed. The client is concerned that there may be voids in the center of the column as well. We don't believe this to be the case, despite having ties passing through the column, however the client still wants to check.
The client would like to use ground penetrating radar equipment, while we advocate using ultrasonic scanners. Do any of you have any comments on the advantages and disadvantages of these two technologies to be used in this case?
Thanks in advance...
The client would like to use ground penetrating radar equipment, while we advocate using ultrasonic scanners. Do any of you have any comments on the advantages and disadvantages of these two technologies to be used in this case?
Thanks in advance...
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RE: GPR vs Ultrasonic
We've used GPR on vertical surfaces of some concrete rigid frame bridges to search for voids. It's a simple process. The technician uses a probe that looks like a paint roller. If the rebar is closely spaced it sometimes creates problems picking up voids behind the bars. I's relatively quick but has depth limitations, about 18"
I also had another project - retaining wall replacement - that used ultrasound (impact-echo) to determine the thickness of the stem (no as-built drawings available). It's not as fast as GPR. It seemed to work; we got a good image of the wall. I say seemed because this part of the project was done by a subconsultant and he hired the ultrasound service. I never witnessed anything; it was about 8 -9 years ago and I don't have the project files in the office anymore.
RE: GPR vs Ultrasonic
Also, recommend a few small cores or small bit drilling to validate NDT.
IC
RE: GPR vs Ultrasonic
(Added)Do you have any photos?
Dik