The instrument used, Sclerometer, and it consists of a hammer driven by a compressed spring that allows to hit an surface.This kind of device is able to record the strength of the rebound hammer impact against the surface under examination by a graduate scale .
In the case of concrete, the index rebound of the hammer will determine the hardness of concrete.
The deduced values is to be considered by analogy the same of concrete jet, whereas the hardness of equal value to both external and internal.
In the case of carbonate surface, hardness outside will be very different from that inside .
Before testing, the surfaces must be free of any material that covering the concrete surface such as plaster, paint, etc. roughness. Every described element will be removed with a carborundum material based that will clean all the examined surface .
The test must be performed by exerting pressure against the area to be examined, keeping the instrument at right angles to the plane and then operate the release device of the hammer which, in the collision, cause the plasticizazione in the area of impact.
The difference between the starting position and the final one ,will be comparated by a diagram that will determine the compressive strength of concrete.