Check the depth of Concrete Cracks

[StructureMan44]

Is there anyway to check the depth of cracks in a monolithic concrete structure? The structure is over 5ft thick in some places and supports large rotating machinery. There are some large cracks and we want to check the depth of the cracks to see if they are deepening over time.

 

[Ingenuity]

Yes.

Non-destructively, ultrasonic testing (using ultrasound transmitter and receiver) is probably the way to go depending on how the crack is accessed for testing - direct or indirect transmission.

Or it may be possible to core sample the crack and visually observe the core - say 2" to 6" diameter concrete core hole centered over the crack for a selected depth. Problem for your situation is that it is deep section (5') and cracks in thicker elements tend to not be straight over such deep sections.

Impact echo (another NDT technique) may also work.

 

[Sawbux]

Ran into similar situation in a sawmill. A large wood chipper foundation developed cracks and the suspicion was that contractor did not put in rebar. Mill was in operation & did not want to shut down to replace the foundation.
The solution was to install steel channels, etc around the outside and clamp with steel rods both external and drilled through to hold the foundation together.
Worked for 30 years, until the mill was closed and torn down!
You may want to consider a similar band-aid approach. Why monitor the crack, if you can piece it back together, inject it or otherwise insure continued functionality?