The rebound hammer test is useful for

a. Approximate estimation of strength

b. Abrasion resistance classification

c. Carbonation depth estimation

d. Uniformity of concrete quality 

Explanation:

Schmidt's Rebound Hammer:

• The rebound hammer is also called as Schmidt hammer.
• The rebound hammer test is a non-destructive testing method of concrete that provides a convenient and rapid indication of the compressive strength of the concrete.
• The Schmidt hammer provides an inexpensive, simple and quick.

Note:

The results are affected by factors such as the smoothness of the surface, size and shape of the specimen, moisture condition of the concrete, type of cement and coarse aggregate, and extent of carbonation of the surface.

The rebound hammer method could be used for:

• assessing the likely compressive strength of concrete with the help of suitable correlations between rebound index and compressive strength,
• assessing the uniformity of concrete,
• The rebound hammer is a surface hardness tester for which an empirical correlation has been established between compressive strength and rebound number.

           But the thickness of concrete cannot be estimated by this method.