Robuta

https://www.nist.gov/publications/nondestructive-evaluation-methods-quality-acceptance-hardened-concrete-structures

Nondestructive evaluation methods for quality acceptance of hardened concrete in structures: | NIST

nondestructive evaluation hardened concrete methods quality acceptance

https://www.sintef.no/en/publications/publication/1635748/

Testing of ring fibres - measurements in fresh and hardened concrete - SINTEF

hardened concrete testing ring fibres measurements