Good acoustic coupling between the transducer face and the concrete surface is necessary to ensure accurate transit time measurement. This done by ensuring that the concrete surface is free from dust and grit and covering the surface with a light or medium grease or other suitable couplant.
A stiffer grease should be used for surface which is moderately rough. Rough surface should either be grounded flat or filled to a level smooth surface with suitable material such as plaster of Paris, cement mortar, etc. before testing.
Direct transmission arrangement is usually employed for more accurate measurement where the two transducers are placed directly opposite each other on the two sides of a concrete wall.
However, examination of concrete by using diagonal paths and semi-direct arrangements, though not very accurate, are suitable for other purposes.
During measurement, it is preferable to avoid path arrangement which contains steel reinforcing bars since pulse velocity measurements made in the vicinity of reinforcing steel may be high.
There is no unique relationship between the pulse velocity and strength as it is influenced by the concrete constituents and curing conditions. Nevertheless, if the mix proportions remain constant and only one type of coarse aggregate is used then it is possible to determine a specific relationship between pulse velocity and strength for in situ concrete.
Besides, moisture conditions also played a significant role in this testing. Owing to these many factors, evaluation of the quality of concrete in structures is usually made on a comparative basis
Determine Concrete Crack Depth using the Proceq PL-200PE – Courtesy of TechRentals