The rebound hammer test is one of the non-destructive tests used to check the compressive strength of concrete

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

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