The Rebound Hammer (RH) method (also known as the Schmitt Hammer method) is used to quickly determine the uniformity of a concrete member with respect to surface strength and stiffness. In addition, from the data collected an estimate of concrete strength may be inferred using standard calibration curves. Testing is carried out in accordance with ASTM standards, by taking the average of 10 measurements at each location after discarding the two extreme values. Note that the results of this test method are heavily influenced by local surface conditions and surface preparation, and thus the estimated strength is only a rough estimate. One typical application of this method is in locating areas of low strength for further evaluation with coring or other methods.
Concrete Uniformity in Compressive Strength and Stiffness at the Surface