The document discusses the rebound hammer test, which is a non-destructive test used to estimate the compressive strength of hardened concrete. It works by measuring the rebound of a spring-loaded hammer after it impacts the concrete surface. A higher rebound number indicates higher compressive strength. The procedure involves firmly pressing the hammer plunger against the concrete surface to trigger the internal spring. The rebound reading can then be correlated to compressive strength using a calibration graph. Advantages are that it is simple, fast, and does not damage the structure. Limitations include only evaluating the surface layer and lack of direct relationship to other concrete properties.

1. Rebound hammer test.
BY BY:
AKSHAY R MANOHAR
MTech-Construction Technology
CIVIL ENGINEERING DEPT.
NMAMIT-NITTE.

2. REBOUND HAMMER
(ASTM C 805-79)

5. CONTENTS
• INTRODUCTION
• PRINCIPLE
• PROCEDURE
• ADVANTAGES
• DIS-ADVANTAGES
• CONCLUSION

6. INTRODUCTION
• The rebound hammer test is one of the non-destructive
tests used to check the compressive strength of concrete .
• An empirical relationship has been determined between
the a absorbed by the concrete when given a high impact
and its compressive strength .
• the rebound hammer is designed to carryout instant non-
destructive test on concrete structure without damage
and gives an immediate indication of the compressive
strength of the concrete using the calibration curve
applied each instrument .
• the hammer is simply pressed firmly against the concrete
whereupon a powerful internal spring is first compressed
and thin tripped to deliver a hammer blow through the
hardened concrete trip to the surface being tested.

7. Rebound hammer test
• Rebound hammer test is done to find out the compressive
strength of concrete by using rebound hammer as per IS:
13311 (Part 2) – 1992.
• Principle of the rebound hammer test is: The rebound of
an elastic mass depends on the hardness of the surface
against which its mass strikes.
• 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 a rebound depends
upon the surface hardness of the concrete.
• The surface hardness and therefore the rebound is taken to
be related to the compressive strength of the concrete.

9. • The rebound value is read from a graduated
scale and is designated as the rebound
number or rebound index.
• The compressive strength can be read directly
from the graph provided on the body of the
hammer.

10. Procedure
• Should be tested against the test anvil.
• Apply light pressure on the plunger and allow
it to extend to the ready position for the test.
• Apply a gradual increase in pressure until the
hammer impacts.
• Take the average of about 15 readings.

11. •Assessing the likely
compressive strength of
concrete .
•Assessing the quality of
concrete in relation to
standard requirements.
• NDT
Rebound Hammer test:

12. Interpretation of Results:
The rebound reading on the indicator scale has
been calibrated by the manufacturer of the
rebound hammer for horizontal impact.
Average Rebound Number Quality of Concrete
>40 Very good hard layer
30 to 40 Good layer
20 to 30 Fair
< 20 Poor concrete
0 Delaminated
Table:- Average Rebound number and quality of concrete

13. RELATIONSHIP B/W REBOUND HAMMER AND
COMPRESSIVE STRENGTH

14. cube compressive strength is N/sq.mm plotted against
rebound number

16. A)Strength Assessment:
• To assess the relative strength of concrete
based on the hardness.
• Casting cubes were tested under controlled
conditions.
• This is due to hardening of concrete surface
due to carbonation.
• It restricted to relatively new structures only.

17. B)Survey of weak and delaminating
concrete:
• It helps to identify relative surface weakness
in cover concrete and to determine the
relative compressive strength of concrete.
• This survey is carried by dividing the member
into well-defined grid points.
• The grid matrix should have a spacing of
approximately 300mm x 300mm.

18. ADVANTAGE
• Simple to use. No special experience
is needed to conduct the test.
• Establishes uniformity of properties.
• Equipment is inexpensive and is
readily available.
• A wide variety of concrete test hammers is
available with an operational range of
M10 to M70.
• For rehabilitation of old Monuments..

20. DISADVANTAGE
• Evaluates only the local point and
layer of masonry to which it is applied.
• No direct relationship to strength or
deformation properties.
• Unreliable for the detection of flaws.
• Cleaning maintenance of probe and spring
mechanism

21. Conclusion
• The rebound value can be measured discretionary,
whereas the number of crushed specimens is limited.
• The combination of both methods is the best and
most reliable procedure to determine the compressive
strength of concrete structures.
• The method does not damage the structure like the
classical method, where cores must be taken for the
evaluation of the compressive strength.
• It is a fast, inexpensive and easy to perform method
using a light and portable test equipment.

22. REFERENCE
• Estimating the Strength of Concrete Using
Surface Rebound Value and Design Parameters
of Concrete Material. Jen-Chei Liu, Mou-Lin Sue and Chang-
Huan Kou*Department of Civil Engineering and Engineering Informatics‚
Chung-Hua University,Hsin Chu, Taiwan 300‚ R.O.C
• CONCRETE TECHNOLOGY – A text book- ML Gambhir.

23. THANK YOU