This document discusses various destructive and non-destructive tests used to evaluate the strength and durability of concrete. Destructive tests involve loading concrete specimens to failure, while non-destructive tests do not break the specimens. Some non-destructive tests discussed include the rebound hammer test, ultrasonic pulse velocity test, and pull-out testing. The results of non-destructive tests can provide estimates of concrete properties like strength, elasticity, and presence of cracks without damaging the structure.

1. CREATED BY : RAJESH GOSWAMI

2. DESTRUCTIVE TEST
NON-DESTRUCTIVE TEST
REBOUND- HAMMER TEST
FACTORS INFLUENCE THE TEST RESULTS
ULTRASONIC PULSE VELOCITY TEST
PULL OUT TESTING
DRILLED HOLE METHOD
PENETRATION RESISTANCE TEST
QUASSI BRITTLE NATURAE OF CONCRETE

3. In case of destructive tests, the concrete
specimens ( cubes, cylinders, beams, etc.) are
loaded till destruction in the laboratory and the
strength properties of concrete are determined
from the test results.
For example,
(1) compression test
(2) tensile strength test
• Splits cylinder test
• Modulus of rupture test
(3) Bond strength test

4. NON-DESTRUCTIVE TESTS
In case of non-destructive tests, the specimen are not loaded to failure.
Non-destructive testing is considered to be a powerful method of evaluating
existing concrete structures with regard to their strength and durability apart
from assessment and control of quality of hardened concrete . These tests are
also performed to determine then presence of internal cracks, micro cracks,
and progressive deterioration in the concrete.
These methods therefore, attempts to measure some other properties
of concrete from which an estimate of its strength ,durability and elastic
properties are obtained. Some such properties of concrete are:
• Hardness
• Resistance to penetration
• Rebound number
• Resonant frequency
• Ability to allow ultrasonic pulse velocity to propagate through it.

5. REBOUND-HAMMER TEST
The SCHMIDT rebound hammer , developed by a Swiss
engineer Ernst Schmidt ,in 1948 is one of the most frequently
used method worldwide for non-destructive testing (NDT) of
concrete structural element.
The test is based on the principle that the rebound of an
elastic mass depends on the hardness of the surface against
which the mass impinges. The hammer consists of a plunger
connected with a spring driven metal mass. The plunger is held
against at 90 to the smooth concrete surface , firmly supported
and pressed . This will impact a fixed amount of energy . Upon
release, by the metal mass or the amount of rebound is noted on
a scale which gives an indication of the concrete strength .
Larger is the rebound , higher is the strength of concrete .

7. FACTORS INFLUENCING THE TEST
RESULTS
Although , rebound hammer saves effort , time and
cost ,it has serious limitation .the results are
significantly influenced by:
1. Mix characteristics like cement type, cement content
2. Smoothness of the surface under test
3. Type of coarse aggregate
4. Size shapes and rigidity of the specimen
5. Age of concrete
6. Moisture condition of the concrete
7. Carbonation of concrete surface
8. Type of mould

8. ULTRASONIC PULSE VELOCITY TEST
The ultrasonic pulse velocity method basically
involves the measurement of velocity electronic
pluses passing through concrete from a
transmitting transducer to a receiving transducer .
The test is based on the principle that the velocity
of sound in a solid material is a function of the
square root of the ratio of its modulus of elasticity
E to its density p . The density and elastic
properties are in turn related to the quality and
strength of the material . The pulse velocities
range from about 3 to 5 km/s . The methods
employ pulses in the frequency range of 15-175
KHz , generated and recorded by electronic
circuits.

10. 1. Transducer arrangement:
There are three ways of measuring pulse velocity through concrete
. They are:
I. Direct transmission
II. Semi-direct transmission
III. Indirect transmission
2. Factors affecting pulse velocity measurement:
I. Smoothness of contract surface
II. Path length
III. Moisture condition of concrete
IV. Temperature of concrete
V. Reinforcing steel

11. 0

12. 3. Application of the ultrasonic testing :
I. Can be used to detect the development of cracks in structures
such as dams , and to check deterioration due to frost or
chemical action.
II. Measurement of concrete uniformity.
III. Detection of ant development of voids or honeycombing in
concrete.
IV. Estimation of strength of concrete.
V. Measurement of the thickness of concrete roads or slabs.
VI. Measurement of elastic modulus.
VII. Studies on durability of concrete.

13. PULL – OUT TESTING
As the names suggests , this method involves the
measurement of the force required to pull-out a specially
shaped steal rod or some similar device from a concrete
surface. There are two basic categories of pull-out , one
which involves an insert having to be cast into the
concrete and another where the insert is fixed into a hole
drilled into hardness concrete.

14. 1.Cast in method (LOK-test) :
The main aim of this technique
is to measure the tensile force
required to pull-out a metal insert
which has been cast into the fresh
concrete . This test is now
commercially knows as LOK-test with
this system there are two main types
of insert , one which is attached
directly
to the formwork and another which is
fixed to a plastic buoyancy cup
which floats on the top surface of the
concrete.

15. 2 .DRILLED HOLE METHOD
It is observed that one of the cast on method
was that the insert needed to be placed before or at
least during process . To overcome this problem
another type of pull-out test was development which
be completed on existing structure.

16. PENETRATION RESISTANCE TEST
The techniques of driving a steel nail into a concrete
surface to provide some from of fixing has been in
use for many years and from this it is well knows
that the depth of penetration achieved is greatly
influenced by the strength of the concrete . Based on
this approach an in-situ test technique was
development in the USA in the mid 1960’s which
involved an explosive charge being used to fire a
specially bolt into the concrete.

18. QUASSI-BRITTLE NATURE OF
CONCRETE
Depending upon the extent of cracking , the
cracks can be classified as macro cracks , microcracks
and semi-microcracks. According ti the location of the
cracks , they are classified as bond cracks , mortar
cracks and aggregate cracks . The bond cracks are
formed at the interface of the aggregate and mortar ,
whereas the mortar cracks are formed through the
mortar and aggregate , respectively.

19. A knowledge of the microcracking of concrete
contributes considerably to the understanding of its
properties , such as its inelastic nature , the
descending portion of the stress-strain curve , the
strength under combined , repeated and sustained
loading etc. The stress –strain curve is related to the
internal cracking . The non-linearity of stress-strain
relation is due to propagation of bond and mortar
cracks.

20. THANK YOU