This standard specifies a method for determining the rebound number of an area of hardened concrete using a spring-driven steel hammer. NOTE 1: The rebound number determined by this method can be used to assess the uniformity of concrete in situ, to delineate zones or areas of poor quality or deteriorated concrete in structures. NOTE 2: The test method is not intended as an alternative for the compressive strength determina- tion of concrete (EN 12390-3), but with suitable correlation, it can provide an estimate of in situ strength.