Rebound Hammer Test (Sachmidt hammer test )

• It is a surface hardness tester for which an empirical correlation has been established between strength and rebound number
• It is based on the principal that the rebound of elastic mass depends on the hardness of surface against which the mass impinges 
• For this test, a rebound hammer also called Sachmidt hammer ,which weight about 1.8 kg and is suitable for both laboratory and field work 
• Is has a spring controlled hummer mass that slids on plunger with in a tubular casing .
• Hammer is forced against the surface of concrete bt the spring and the distance of rebound is measured on a scale which give indication of concrete strength 
• This test is suitable for the concrete having strength in the range of 20-26 MPa 
• Results are affected by facters sach as smoothness of surface size and shape of specimen , moisture condition of the concrete ,type of cement and coarse aggregate and extent of extent of carbonation of surface