Non-destructive testing methods: damage-free quality check

Crosshole Sonic Logging (CSL) and Tomography are testing methods based on ultrasound. The best-known use of this technology is to determine the quality of diaphragm wall joints. But it can also be used to determine the quality of bored piles, grout solids and other (cement-based) structures and to locate irregularities without damaging the structure. In principle, the testing methods work from the interior of the structure, in individual pipes that have been concreted into the structure beforehand. Above ground, it is also possible to make external sound measurements.

CSL 1 acc_over


CSL is used in situations where the quality of concrete structures cannot be determined visually. CSL quickly produces a clear picture. Tomography, on the other hand, is primarily used to define suspect areas more effectively. What makes the measuring system unique is its graphical presentation of the measurement data. Using the colour plots, the quality can be determined easily and immediately.


Ultrasound can be used to test a wide variety of structures. Whereas CSL and tomography are used internally for foundations, this can also be done externally with other sensor types. As long as a structure can be accessed from two sides, no devices need to be included in the structure.

These measurement methods can be used to check a wide range of concrete structures for:

  • cracks
  • entrapped air
  • entrapped soil
  • poor-quality concrete
  • anomalous diameters of piles
  • foundation depths
  • general foundation integrity

Preparation and implementation

The nucleus of the testing method is a multi-functional integrated measurement computer that is suitable for a rough construction environment. Strukton Survey & Monitoring helps you to make the right choices: we offer advice on equipment and preparation in the design stage and we carry out inspections and measurements. We then interpret and visualise the data. Furthermore, we have extensive expertise at our disposal that we can draw upon to actively help devise new applications and follow-up measures.


  • Accurate measurements by means of a high measurement resolution (measurements at 1.4cm intervals)
  • Real-time data visualisation for instantaneous assessment of the quality
  • Minimal processing time for reports
  • To a depth of 50 metres and unlimited width
  • Powerful 3D visualisation by means of tomography (image and film options)
  • Accelerated data acquisition using two receivers