Effect of Curing and Deterioration on Stress Wave Velocities in Concrete

Measuring the thickness of concrete elements in the field can be challenging. In many cases, such measurements must be made from one side due to a lack of access to the opposite face. One technique commonly implemented in these situations is the impact echo method, which requires advance knowledge of the compression, or P wave, velocity through the concrete at the point of interest. Common practice is to measure the near surface P-wave velocity at that point and then use this velocity to represent the through thickness P-wave velocity in the calculation of thickness. However, the relationship between near surface P-wave velocities and through thickness P-wave velocities can vary significantly under different exposure conditions. Using near surface P-wave velocity to represent through thickness P-wave velocity is not necessarily a valid assumption and should only be done when further information is available to substantiate the relationship. It is possible to detect damage due to sulfate attack in concrete specimens using P-wave velocity measurements, though actual identification of the nature of that damage is not feasible.