Ultrasonic Test Equipment

The ultrasonic test equipment is used to provide information on the uniformity of concrete, cavities, cracks and defects. The ultrasonic test equipment is based on the pulse velocity method. It is recommended to measure the distance (path length) between the transducers as accurately as possible before the testing. The standard measuring procedure is:

* Apply the couplant. It is very important to ensure adequate acoustic coupling of the transducers to the surface under test. A thin layer of couplant should be applied to the transducers and the test surface. In some cases it may be necessary to prepare the surface by smoothing it.

* Position the transducers. Three transducer arrangements are commonly used:

1. The direct arrangement

2. Semi-direct arrangement

3. Indirect or surface arrangement

* Wherever possible it is recommended to use the direct arrangement as this ensures the maximum signal transmission between the transducers. The semi-direct arrangement is less sensitive than the direct, but more sensitive than the indirect arrangement. The path length is the distance between the centers of each transducer. The indirect method is particularly useful for determining crack depth, surface quality or in the case when only one surface is accessible.

* Perform the measurement

* Save the result

For compound measurements and uniformity testing a test grid should be drawn on the surface. Rebars affect the ultrasonic measurements as the signal will travel faster through the rebar than through the concrete. The location of rebars should be determined and ultrasonic tests should be positioned so as to avoid them. The British Standard 1881 Part 203 gives information on the effect of rebars on the expected results.

by Carla Fijnvandraat