This presentation describes 6 methods to check concrete sample by performing non destructive testing. 1. Rebound hammer 2. Dye penetration test 3. Pull out test for concrete 4.Half cell potentiometer test 5.Rebar scanner 6 ultrasonic pulse velocity test

1. SEMINAR
KRISHNA ENGG COLLEGE
RCE-851
Btech (civil)
ROLL NO: 1716100003
BY: AKASH BHARDWAJ
NON DESTRUCTIVE
TESTING

2. INDEX
◦Introduction
◦Rebound hammer test
◦Dye penetration test
◦Pullout test method for RCC
◦Rebar scanner
◦Ultrasonic pulse velocity
◦Half cell potentiometer

3. INTRODUCTION
• Nondestructive testing or non-destructive testing
(NDT) is a wide group of analysis techniques used
in science and technology industry to evaluate the
properties of a material, component or system
without causing damage. •
• Also known as nondestructive examination (NDE),
nondestructive inspection (NDI), and nondestructive
evaluation (NDE).

4. 1. REBOUND HAMMER
IS-13311 (Part 2):1992 (Reaffirmed- May 2013) “
Objective:
The rebound hammer method could be used for:
• assessing the likely compressive strength of concrete with the help of suitable co-relations
between rebound index and compressive strength.
• assessing the uniformity of concrete.
• assessing the quality of the concrete in relation to standard requirements.
• assessing the quality of one element of concrete in relation to another.

5. Principle:
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 rebound is read off along a
graduated scale and is designated as the rebound number or rebound
index.

6. Test Procedure :
1. For testing, smooth, clean and dry surface is to be selected. If loosely adhering scale is present, this
should be rubbed of with a grinding wheel or stone. Rough surfaces resulting from incomplete
compaction, loss of grout, spalled or tooled surfaces do not give reliable results and should be avoided.
2. The point of impact should be at least 20 mm away from any edge or shape discontinuity.
3. For taking a measurement, the rebound hammer should be held at right angles to the surface of the
concrete member. The test can thus be conducted horizontally on vertical surfaces or vertically upwards
or downwards on horizontal surfaces. If the situation demands, the rebound hammer can be held at
intermediate angles also, but in each case, the rebound number will be different for the same concrete
4. Rebound hammer test is conducted around all the points of observation on all accessible faces of the
structural element. Concrete surfaces are thoroughly cleaned before taking any measurement. Around
each point of observation, six readings of rebound indices are taken and average of these readings after
deleting outliers as per IS:8900-1978 becomes the rebound index for the point of observation.

7. Interpretation Of Result
1. The rebound hammer method provides a convenient and rapid
indication of the compressive strength of concrete by means of
establishing a suitable correlation between the rebound index and
the compressive strength of concrete. the procedure of obtaining
such correlation is given in graph.
2. It is also pointed out that rebound indices are indicative of
compressive strength of concrete to a limited depth from the
surface. If the concrete in a particular member has internal
microcracking, flaws or heterogeneity across the cross-section,
rebound hammer indices will not indicate the same.

8. Dye penetration test
1.This module is intended to provide an introduction to the NDT method
of penetrant testing.
2.Penetrant Testing, or PT, is a nondestructive testing method that builds on
the principle of Visual Inspection.
3.PT increases the “visibility ” of small discontinuities that
the human eye might not be able to detect alone.

9. WORKING PRINCIPLE
◦In penetrant testing, a liquid with high surface wetting characteristics is applied to
the surface of a component under test.
◦The penetrant “penetrates” into surface breaking discontinuities via capillary
action and other mechanisms.
◦Excess penetrant is removed from the surface and a developer is applied to pull
trapped penetrant back the surface.
◦With good inspection technique, visual indications of any
discontinuities present become apparent.

10. 6 Steps of Penetrant Testing
1. Pre-Clean
2. Penetrant Application
3. Excess Penetrant Removal
4. Developer Application
5. Inspect/Evaluate
6. Post-clean

11. COMPLETE PROCESS:

12. ADVANTAGES:
•Can be used on a wide range of material types.
•Large Relative ease of use.
•Areas or large volumes of parts/materials can be inspected rapidly and at low
cost.
•Parts with complex geometries are routinely inspected.
•Indications are produced directly on surface of the part providing a visual image
of the discontinuity.
•Initial equipment investment is low.
•Aerosol spray cans can make equipment very portable.

13. Limitations :
•Only detects surface breaking defects.
•Requires relatively smooth nonporous material.
•Precleaning is critical. Contaminants can mask defects.
•Requires multiple operations under controlled conditions.
•Chemical handling precautions necessary (toxicity, fire, waste).
•Metal smearing from machining, grinding and other operations inhibits detection.
Materials may need to be etched prior to inspection.
•Post cleaning is necessary to remove chemicals.

14. 3. Pull Out Test of Concrete
◦ The test measures the force required to pull out a previously
cast in steel insert with an embedded enlarged end in the
concrete. In this operation, a cone of concrete is pulled out
and the force required is related to the compressive strength
of concrete.

15. Test Procedure:
◦
◦ Pull out insert (shown in fig) is embedded in plain concrete during
pouring. When the strength is required to be determined, the force
is applied at the embedded end. The force required to pull out the
assembly is measured.
THERE ARE TWO METHODS:
1. IN SITU
2. DRILLED

16. EVALUATION
• The pull out assembly is pulled with a lump of concrete, which is
subjected to tension and shear and the force required to pull out is
related to shearing strength of concrete and not to the compressive
strength.
• Ratio of pull out force to compressive strength decreases slightly with
increase in the level of strength.
• Pull out may not be carried out till completion. It my be sufficient to
apply a predetermined force to the embedded rod and if it is not pulled
out, a given strength is assumed to exist.

17. Advantage
◦ The pull out test is superior to Schmidt hammer and penetration resistance test
because larger volume and greater depth of concrete are involved in the test. Repair
of concrete after test is also required. Relation between compressive strength and pull
out force is shown in figure below.
Limitations
• Steel rod assembly has to be embedded in concrete during pouring and hence test
cannot be undertaken at later ages.
• Repair of damaged concrete is required.

18. 4. REBAR SCANNER
• Rebar detector is one of the NDT, which are used to locate
the steel bar embedded in concrete before drilling and before
taking core test.
• It is the easiest and fastest ways for detecting reinforcing bar
in concrete. It is widely used before coring or drilling holes to
find “safe spots” . • It will indicate rebar location, direction and
also will give an indication of the depth of concrete cover.

19. MECHANISM
◦ A rebar detector works on the principle that the steel within the concrete will
be affected by a magnetic field that is applied by the detector.
◦ By assuming a set magnetic property for all steel reinforcing bars and using a
given bar size, the detector can predict the depth and location of the
reinforcing bars.
◦ The signal received will increase with increasing bar size and decrease with
increasing cover.
◦ To locate the bar position, the distance to the bar is minimized, indicating that
the rebar detector is directly over a piece of the reinforcing steel.

20. Procedure
◦ The instrument is laid at the surface of the column or slab.
◦ An Instrument is moving from the left to right and then from
the bottom to up to get the position of the reinforcement.
◦ Once the locations of rebar are found, a masonry drill is used
to locate the total cover to the rebar.

21. SIGNIFICANCE:
◦ Hitting a rebar however boring into the reinforced concrete
moreover taking core may be destroy the drilling instrument
and can severely weaken the concrete structure. •
◦ This is an instrument for rebar detection that quickly and
accurately determines the location of the reinforcing bars in
the concrete.

22. 5.Ultrasonic Pulse Velocity (UPV)
◦ This test is done to assess the quality of concrete by ultrasonic pulse
velocity method as per IS: 13311 (Part 1) – 1992.
PRINCIPLE
◦ The method consists of measuring the time of travel of an ultrasonic
pulse passing through the concrete being tested. Comparatively higher
velocity is obtained when concrete quality is good in terms of density,
uniformity, homogeneity etc.

23. Procedure to determine strength of hardened
concrete by Ultrasonic Pulse Velocity:
◦ Preparing for use: Before switching on the ‘V’ meter, the transducers should be connected to the sockets marked
“TRAN” and ” REC”.
◦ Set reference: A reference bar is provided to check the instrument zero. The pulse time for the bar is engraved on
it. Apply a smear of grease to the transducer faces before placing it on the opposite ends of the bar. Adjust the
‘SET REF’ control until the reference bar transit time is obtained on the instrument read-out.
◦ Range selection: For maximum accuracy, it is recommended that the 0.1 microsecond range be selected for path
length up to 400mm.
◦ Pulse velocity: Having determined the most suitable test points on the material to be tested, make careful
measurement of the path length ‘L’. Apply couplant to the surfaces of the transducers and press it hard onto the
surface of the material. Do not move the transducers while a reading is being taken, as this can generate noise
signals and errors in measurements. Continue holding the transducers onto the surface of the material until a
consistent reading appears on the display, which is the time in microsecond for the ultrasonic pulse to travel the
distance ‘L’. The mean value of the display readings should be taken when the units digit hunts between two
values.

24. ◦ Pulse velocity=(Path length/Travel time)
◦ Separation of transducer leads: It is advisable to prevent the two
transducer leads from coming into close contact with each other
when the transit time measurements are being taken. If this is not
done, the receiver lead might pick-up unwanted signals from the
transmitter lead and this would result in an incorrect display of the
transit time.

25. Interpretation of Results
The quality of concrete in terms of uniformity, incidence or absence of internal flaws,
cracks and segregation, etc are Indicators of the level of workmanship employed, can
thus be assessed using the guidelines given below, which have been evolved for
characterizing the quality of concrete in structures in terms of the ultrasonic pulse
velocity.

26. 6. Half cell potentiometer
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OBJECTIVES
• Locate corrodingrebars
• Identify the position for further destructive analysis (cores
for chloride analysis, inspection windows to visually
examine the corrosionstate of the rebars etc.
• Evaluate the efficiency anddurability of repair work
• Design an anode layout of cathodic protection systems or
electrochemical restorationtechniques

27. Half cell potential apparatus:
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• Voltmeter
• Reference Electrode
• Connector toreinforcing steel

28. OBJECTIVES OF HALF CELLPOTENTIAL
TEST:
◦ To evaluate potential of concrete in promoting corrosion activity of
reinforcement by Half Cell Potential test.
◦ To evaluate reinforcing steel in concrete that has carbonated to the
level of the embedded steel
◦ To evaluate indoor concrete that has not been subjected to frequent
wetting unless it has been protected from drying after casting
◦ To compare corrosion activity in outdoor reinforced concretes of highly
variable moisture or oxygen content, or both, at the embedded steel

29. Mechanism of Chloride Attack:
◦ Ingress of Cl- and O2 , Formation of OH-Preferential migration of Cl- to neutralize Fe++ formed
within the pit and formation of FeCl2.
◦ Hydrolysis of FeCl2 and acid formation ( HCl ) which accelerates further attack on metal.
Intensive localized corrosion within the pit leading to failure.
Corrosion Mechanism:
◦ Corrosion of Steel in Concrete is an Electrochemical process. In Steel, one part becomes anode
and other part becomes cathode connected by electrolyte in the form of pore water in the
hardened cement paste. Positively charged Fe++ at the anode passes into solution.
◦ Negatively charged free electrons e- passes through the steel into cathode where they are
absorbed by the constituents of the electrolyte and combine with water & oxygen to from
hydroxyl ions (OH)-. (OH)- travel through the electrolyte and combine with the ferrous ions to
form ferric hydroxide and by further oxidation converted to rust.

30. FACTORS AFFECTING TEST RESULTS
◦ Wetness of surface
◦ Carbonation
◦ Electric Current
INTERPRETATION OF TEST RESULTS
◦ If potentials over an area are more positive than -0.20 VCSE, there is a greater
than 90% probability that no reinforcing steel corrosion is occurring in that area
at the time of measurement.
◦ If potentials over an area are in the range of -0.20 to-0.35 V CSE, corrosion
activity of the reinforcing steel in that area is uncertain.
◦ If potentials over an area are more negative than -0.35 VCSE, there is a
greater than 90 % probability that reinforcing steel corrosion is occurring in that
area at the time of measurement.