Rebound Hammer Test Result Calculation

The objective of rebound hammer is to determine the compressive strength of concrete with rebound hammer according to IS: 13311 (Part 2) - 1992.

The fundamental concept of the rebound hammer test.

The rebound of an elastic mass is based on the rigidity of the surface against which its mass hits. While pressing the plunger of the rebound hammer against the surface of the concrete, the Spring-controlled mass rebounds and the span of such a rebound is influenced by the surface hardness of the concrete.

The surface hardness as well as the rebound is considered to be incidental to the compressive strength of the concrete. The rebound value is determined from a graduated scale and is indicated as the rebound number or rebound index. The compressive strength is found directly from the graph presented on the body of the hammer.

Significance of Residual Life Assessment: RLA carried out to keep up the well-organized operation of a process plant unit and get rid of failure of critical equipments, which create expensive downtime issue.

Such equipments comprise of pressure vessels, piping, storage tanks, valves, pumps, compressors, boilers, turbines etc. One common feature of all such equipments is their operation under very difficult conditions ranging from high temperature, pressure etc.

The significance of carrying out RLA studies also derives from the regulations which exist for different industrial equipments, like boilers, turbines etc.

Also Read: Some vital points for site civil engineer

How To Find out Strength Of Hardened Concrete with Rebound Hammer:

• Prior to conduct a test, the rebound hammer should be examine properly against the test anvil, to obtain trustworthy results, for which the manufacturer of the rebound hammer specifies the range of readings on the anvil useful for several types of rebound hammer.

• Provide light pressure on the plunger to set it free from the locked position and facilitate it to expand to the ready position for the test.

• Press the plunger against the surface of the concrete by retaining the instrument perpendicular to the test surface. Raise the pressure slowly unless the hammer blows. (refrain from touching the button at the time of depressing the plunger. Press the button after impact, if it is not possible to note the rebound reading in that position.) Select the average of about 5 readings.

Rendition of Results: The rebound reading on the indicator scale is measured with the manufacturer of the rebound hammer for horizontal impact i.e. on a vertical surface, to specify the compressive strength. If provided in any other position, exact rectification as submitted by the manufacturer should be considered.

Equipment used: A simple equipment alias rebound hammer or schmidt hammer is utilized in this test.

Surface hardness calculated throughout the test provides the idea regarding the soundness and quality of concrete cover. Locations with very low rebound members specify weak surface concrete and it is impacted by erosion.