REBOUND HAMMER TEST
IS:13311 (Part-2) 1992
This Indian Standard was adopted by the Bureau of Indian Standards, after the draft finalized by the Cement and Coacrete Sectional Committee bad b’een approved bg&+fivil Engineering Division
Council.
There are occasions when the various perfortiance characteristics of concrete in a structure are
required to be assessed. In most of the cases, an estimate of strength of concrete in the structure is needed, although parameters like overall quality, uniformity, etc, also become important in others. The various methods that can be adopted for in-situ assessnhent of strength properties of concrete depend upon the particular aspect of strength in question. For example, if the load-carrying capacity of structural ensemble is to be assessed, carrying out a full-scale load test 8s per IS 456 : 1978 ‘Code of practice for plain and reinforced concrete ( third revision )’ or IS 1343’: 1980 ‘Code of practice for prestressed concrete (first revision )’ is the most direct way; on the other hand when the actual compressive strength of a concrete in the structure is to be measured, core testing as per IS 516 : 1959 & Method of test for strength of concrete’ is more reliable. However, both these methods are relatively cumbersome and the latter method may leave the structure damaged locally in some cases, Use is, therefore, made of suitable non-destructive tests, which not only provide an estimate of the relative strength and overall quality of concrete in the structures, but also help in deciding whether more rigorous tests like load testing or core drilling at selected locations are required.
There a’re various such non-destructive testing methods which can be broadly classified as those which measure the overall quality of concrete, for example dynamic or vibration methods like resonance frequency and ultrasonic pulse velocity tests; and those which involve measurement of parameters like surface hardness, rebound, penetration, pull-out strength, etc, and are believed to be indirectly related to the compressive strength of concrete. In addition, radiographic, radiometric, nuclear, magnetic and electrical methods are also available. Since such non-destructive tests are at best indirect methods of monitoring the particular characteristic of concrete and the measurements are influenced by materials, mix and environmental factors, proper interpretation of the results calls for ce1 tain degree of expertise. It is more so, when the data on the materials and mix proportions used in the construction are not available as is often the case.
SCOPE
This standard covers the object, principle, apparatus and procedure of rebound hammer test method. In addition, influence of test conditions and some general guidance on the interpretation of test results are also given. NOTE - In view of the limitations of each method of non-destructive testing of concrete, it is essential that the results of tests obtained by one method .should be complimented by other tests and each method should be adopted very carefully.
REFERENCES
The following Indi‘an standards are necessary adjuncts to this standard. IS No. Title 516 : 1959 Method of test for strength of concrete Table 1 Impact Energy for Rebound Hammers for Different Applications ( Clause 4.1 ) Sl No. Application Approximate Impact Energy Required 8900 : 1978 Criteria for rejection of outlying observations
OBJECT AND PRINCIPLE OF TEST
301 Object
The rebound hammer method could be used for:
i) assessing the likely compressive strength
of concrete with the help of suitable corelations between rebound index and
compressive strength,
ii) assessing the uniformity of concrete,
iii) assessing the quality of the concrete in
relation to standard requirements, and
iv) assessing the quality of one element of
concrete in relation to another.
3.2 Principle of Test
When the plunger of rebound hammer is pressed against the surface of the concrete, the spring controlled mass rebounds and the extent of such rebound depends upon the surface hardness of concrete. The surface hardness and therefore the rebound is taken to be related to the compressive strength of the concrete. The