Abstract
This paper describes results of the research on the problems of concrete strength estimation by rebound hammer tests. The relationship between the rebound number and the concrete hardness obtained by the experiments almost coincides with the one theoretically derived. Accordingly, the rebound number expressed hardness, including the experimental error that affected by the random change of the impact energy loss in concrete. The energy loss can cause increased error of hardness in high strength concrete. It was also shown that the hardness was approximately proportional to compressive strength, which means the hardness was a possible index to evaluate compressive strength of concrete.
