This document discusses non-destructive testing methods for hardened concrete, including rebound hammer tests and ultrasonic pulse velocity tests. The rebound hammer test measures surface hardness to estimate compressive strength within 50mm depth. The ultrasonic pulse velocity test measures the time for an ultrasonic pulse to pass through concrete, which depends on density, elasticity, and Poisson's ratio, and can assess uniformity and detect flaws. Both methods provide preliminary strength assessments but core tests may be needed for confirmation.

1. Non-destructive
Tests of hardened
concrete
Prepared by :
Parth Desani (116470306049)

2. index
• Process of concrete manufacture
• Hardened Concrete
• What is Non – Destructive test ?
• Importance of Non – Destructive Test
• Need of Non – Destructive Test
• Non – Destructive Tests for hardened concrete
• Rebound Hammer Test
• Rebound Hammer
• Procedure
• Advantage
• Interpretation
• Ultra Sonic Pulse Velocity Test
• USPV Test
• How it works ?
• Applications and Limitations
• Interpretations
• Advantages and Disadvantages

3. Process of concrete manufacture
• The process of concrete manufacture is
simply:
• Aggregates + Cement + Water + Chemical
Admixtures = Concrete
• However, the place of manufacture can either
be at a construction site as a small batch
produced in a portable concrete mixer or at a
large batching plant at the construction site or
transported by concrete mixing truck from a
concrete plant some distance from the
construction site. In the latter case the
concrete is called ready mix concrete.

4. Hardened concrete
• The concrete which loses its plasticity completely after a time and
gets strength is called hardened concrete.
• Durability and strength increase with lower water content, higher
cement content, higher densities, extended moist curing and correct
type of cement.
• Therefore, if water-to-cement ratio is altered by raising water
content, the concrete will be less durable and weaker.
• Proper compaction will also give higher densities and improve
strength and durability.
• Curing time is also important. The longer the concrete is cured and
kept damp, the stronger and more impermeable and durable it will
be.

5. What is Non – destructive test ?
• Non destructive testing is a technique for checking
structural integrity after concrete hardening without
damaging it.
• Non-destructive testing can be applied to both old
and new structures. For new structures, the principal
applications are likely to be for quality control or the
resolution of doubts about the quality of materials
or construction.
• The testing of existing structures is usually related
to an assessment of structural integrity or adequacy.

6. Importance of non-destructive
testing
• Strength on concrete depends on material, proper mixing
& also workmanship at the time of placing.
• If destructive testing alone is used, for instance, by
removing cores for compression testing, the cost of
coring and testing may only allow a relatively small
number of tests to be carried out on a large structure
which may be misleading.
• Non-destructive testing can be used in those situations as
a preliminary to subsequent coring.

7. Need of non-destructive testing
• Typical situations where non-destructive testing may be
useful are, as follows:
• Removing uncertainties about the acceptability of the material
supplied
• confirming or negating doubt concerning the workmanship
involved in batching, mixing, placing, compacting or curing of
concrete
• monitoring of strength development in relation to formwork
removal, cessation of curing, pre-stressing, load application or
similar purpose
• location and determination of the extent of cracks, voids,
honeycombing and similar
• determining the position, quantity or condition of reinforcement

8. Non – Destructive tests for
hardened concrete
• Surface Hardness Test
• Rebound Hammer Test
• Ultrasonic Pulse Velocity Test
• Radioactive Methods
• Nuclear Methods
• Magnetic Methods
• Electrical Methods

9. Rebound hammer test

10. Rebound Hammer
The schematic diagram showing various parts of a
rebound hammer are
1. Concrete surface
2. Impact spring
3. Rider on guide rod
4. Window and scale
5. Hammer guide
6. Release catch
7. Compressive spring
8. Locking button
9. Housing
10. Hammer mass

11. Methodology
• Identify test Locations.
• Clean the concrete surface thoroughly (remove plaster, if
present ).
• Press hammer and release.
• Note down the reading.
• Take an average of multiple readings.
• Repeat the test on multiple areas of the element if
necessary.
• Test at different members of the structure.

12. • The Rebound Hammer test measures surface
hardness only (upto about 50 mm depth).
• In order to assess continuity inside the element,
UPV test is recommended.
• The estimated strength may very from actual
strength about +/- 10%.
• In order to confirm the findings of tests, core tests
may be conducted on a select sample of element

13. REBOUND HAMMER
TEST
•This is a simple, handy tool, which can be used to
provide a convenient and rapid indication of the
compressive strength of concrete.
•The elastic mass depends on the hardness of the
surface.
•It is related to the compressive strength of the
concrete.
•The rebound value is designated as the rebound
number or rebound index.
The results are significantly affected by :
A)Mix characteristics.
B)Angle of inclination of direction of hammer.
C)Member characteristics.

14. Advantages
•Assessing the likely compressive
strength of concrete .
•Assessing the quality of concrete
in relation to standard
requirements.

15. Interpretation
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
30 to 40 Good
20 to 30 Fair
< 20 Poor
0 Delaminated
Table:- Average Rebound number and
quality of concrete

17. Ultrasonic pulse
velocity test

18. Ultrasonic pulse velocity test
It measures the time of travel of an ultrasonic pulse
passing through the concrete.
The apparatus for ultrasonic pulse velocity measurement
consists of the following:
(a) Electrical pulse generator
(b) Transducer – one pair
(c) Amplifier
(d) Electronic timing device
Principle:
• The velocity of an ultrasonic pulse through any material
depends upon the density, modulus of elasticity and Poisson’s
ratio of the material.

20. Methodology:
• Clean the concrete surface thoroughly (on plaster or without
plaster).
• Apply grease on the concrete surface where test is to be conducted.
• Press probes on the surface of the structural element to remove air
gaps.
• Note down the distance between the 2 probes.
• Read time taken for the ultrasonic pulse from the instrument.
• Calculate Velocity = distance / time
• Repeat the test on multiple areas of the element if necessary.
• Test at different members of the structure.

21. Applications & Limitations
•The pulse velocity method is an
ideal tool for establishing
whether concrete is uniform.
•Applied to both existing
structures and those under
construction.
•High pulse velocity readings are
generally indicative of good
quality concrete.

22. Interpretation
• To determine the quality & homogeneity of the concrete
structures.
• To determine the existence of the flaws ,cracks & voids
in concrete structures.
Table: Velocity Criterion for concrete Quality Grading
(IS :13311 Part I ).
S.N
o
Pulse velocity in cross
probing (km/sec)
Concrete
Quality
Grading
1. Above 4.5 Excellent
2. 3.5 to 4.5 Good
3. 3.0 to 3.5 Medium
4. Below 3.0 Doubtful

23. Advantages and disadvantages
Advantages:
High penetrating power.
High sensitivity.
Greater accuracy
Some capability in
estimating the size , shape ,
nature of the flaws.
portability
Disadvantages:
• Manual operation requires
careful attention by
experienced technicians
• Difficulty in inspecting
the parts which are
irregular.
• Requirement of the
couplants.
• Test objects should be
water resistant.