SURFACE STRENGTH PROFILE – REBOUND HAMMER METHOD

 

SURFACE STRENGTH PROFILE – REBOUND HAMMER METHOD

Rebound hammer test is a quick method to assess the Quality / strength of in-situ concrete and prestressed concrete.As this test does not involve any time of destruction of concrete or structure thus known as non destructive testing of concrete structures. Rebound Hammer Test will be carried out at prejudged location to assess the surface hardness / quality and strength of in-situ concrete and prestressed concrete. When testing, the 'Rebound Number’ is measured which depends on the strength of surface interior zone concrete.

Since the strength of the surface zone concrete determines the strength of the interior concrete, the rebound number gives an indication of the strength of the concrete section. If the strength of concrete is high, then the rebound number reading is also high. When the plunger of the rebound hammer is pressed against the surface of the concrete, the spring controlled mass rebounds and the extent of such rebound depends upon the hardness of concrete. The rebound is read off along a graduated scale recorded and is designated as the rebound number. The tests will be conducted using Schmidt Rebound Hammer as per the guidelines in IS: 13311(Part 2)-1992.

 As per site condition and client request the section shall be divided into parts / lifts wise and suitable reading shall be taken.

STEPS-

For the   successful test, following steps are followed

(i) Before starting the rebound hammer test, the rebound hammer should be tested against the test anvil. This step will ensure the correctness of anvil different types of rebound hammer test according to range of readings quantified by the manufacturer.

(ii) Light force should be applied on the plunger in order to release it from inaccessible position. It will further permit plunger for the commencement of the assessment.

(iii) The next stage is to press plunger against the surface of the concrete while keeping the instrument perpendicular to the test surface. In the process, slow increase needs to be applied until the hammer impacts are executed. Be careful that, while depressing the plunger not to touch the button.

(iv) An avg. of 15 readings should be taken during the assessment.

On the base of readings observed in the graph, calculation of the compressive strength of concrete will become easier.