The rebound hammer test is used to determine the compressive strength of concrete by using a rebound hammer. It is also called the Schmidt hammer test or Swiss hammer test. This test comes under the category of Non-Destructive Testing of Concrete.
Table of Contents
Purpose of Rebound Hammer Test
There are there main purposes of this test.
- To calculate the compressive strength of the concrete by relating the rebound index and the compressive strength
- To evaluate the uniformity of the concrete
- To check out the quality of the concrete based on the standard specifications
The principal of Rebound Hammer Test:
When the plunger of the Schmidt hammer is pressed against the concrete surface, the spring-controlled mass rebounds and the extent of this rebound depends upon the hardness of the concrete surface. The surface hardness and therefore the rebound is taken to be related to the compressive strength of the concrete. The rebound is read off along a graduated scale and is designated as the rebound number or rebound index.
The compressive strength of the concrete can be read directly from the graph on the body of the rebound hammer.
The concrete surface at the test should be smooth, and dry. There should not be any honeycombing in the concrete.
Results:
| Average Rebound Number | Concrete Quality |
|---|---|
| Greater than 40 | Excellent |
| 30-40 | Good layer |
| 20-30 | Fair |
| Less than 20 | Poor |
| Zero | Delaminated |