Schmit Rebound Hammer

Schmit Rebound Hammer INTRODUCTION

The Schmidt rebound hammer  also known as the rebound hammer test, is principally a surface hardness tester. It works on the principle that the rebound r ebound of an elastic mass depends on the t he hardness of  the surface against which the mass impinges. impinges. There is little apparent theoretical relationship relationship between the strength of concrete and the rebound number of the hammer. The hammer weighs about 1.8 kg and is suitable for use both in a laboratory and in the field. A schematic cutaway view of the rebound hammer is shown in . The main components include the outer  body, the plunger, the hammer mass, and the main spring. Other features f eatures include a latching mechanism that locks the hammer mass to the plunger rod and a sliding rider to measure the rebound of the hammer  mass. The rebound distance is measured on an arbitrary scale marked from 10 to 100. The rebound distance is recorded as a “rebound number” corresponding corresponding to the position of the rider on the scale.

Figure 1 : Schmidt hammer 

Figure 2 : Working principle of a Schmidt hammer 

ADVANTAGES

DISADVANTAGES

Simple to use. No special experience is needed to

Evaluates only the local point and layer (wythe) of 

conduct the test.

masonry to which it is applied.

Establishes uniformity of properties

No direct relationship to strength or deformation properties.

Equipment is inexpensive and is readily available. It is relatively simple and inexpensive to conduct a large number of tests. The equipment for the test is readily available.

Unreliable for the detection of flaws

REFERENCES

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ISRM Suggested method for determination of the Schmidt hammer rebound hardness: Revised version Adnan Aydin,2007 Department of Geology and Geological Engineering, The University of Mississippi, University, MS 38677, USA. Application of Schmidt rebound number for estimating rock strength under specific geological conditions,S.R Torabi,2010