Properties and strength of materials

3. 3
TYPES OF TESTING OF CONCRETE
STRUCTURES
DESTRUCTIVE
TESTING
NON-
DESTRUCTIVE
TESTING
Introduction

4. 4
Destructive Testing
• In destructive testing, or (Destructive Physical Analysis
DPA) tests are carried out to the specimen's failure, in
order to understand a specimen's structural
performance or material behaviour under different
loads.
• These tests are generally much easier to carry out, yield
more information, and are easier to interpret than
nondestructive testing.
• Destructive testing is most suitable, and economic, for
objects which will be mass-produced, as the cost of
destroying a small number of specimens is negligible.

5. 5
• It is usually not economical to do destructive testing
where only one or very few items are to be produced
(for example, in the case of a building).
• Analyzing and documenting the destructive failure
mode is often accomplished using a high-speed
camera recording continuously (movie-loop) until the
failure is detected.
• Detecting the failure can be accomplish using a
sound detector or stress gauge which produces a
signal to trigger the high-speed camera. These high-
speed cameras have advanced recording modes to
capture almost any type of destructive failure.

6. 6
• These high-speed cameras have advanced
recording modes to capture almost any type of
destructive failure.
• After the failure the high-speed camera will stop
recording.
• The capture images can be played back in slow
motion showing precisely what happen before,
during and after the destructive event, image by
image.

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DESTRUCTIVE TESTING
 Stress Testing
 Crash Testing
 Hardness Testing
Destructive testing of a 6-storey concrete building using a shake table

8. 8
TYPICAL DEFECTS IN CONCRETE STRUCTURES
Cracks due to concrete settling Sketch of exposed aggregate

9. 9
Cracks due to differential settlement Rusting of reinforcing bars
TYPICAL DEFECTS IN CONCRETE STRUCTURES

10. 10
Effect of atmospheric conditions
Cracks due to bending and shear
stresses
TYPICAL DEFECTS IN CONCRETE STRUCTURES

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1
• Some types of destructive testing:
 Stress tests
 Crash tests
 Hardness tests
 Metallographic tests
• Benefits of Destructive Testing (DT)
 Verifies properties of a material
 Determines quality of welds
 Helps you to reduce failures, accidents and
costs
 Ensures compliance with regulations

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2
Non Destructive Testing (NDT)

13. 1
3
 Nondestructive testing (NDT) is a wide group of
analysis techniques used to evaluate the properties of
a material, component or system without causing
damage.
 Nondestructive examination (NDE)
 Nondestructive inspection (NDI)
 Nondestructive evaluation (NDE)
Definition

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4
 Does not permanently alter the article being inspected
 Save both money and time in product evaluation,
troubleshooting and research
 Can be used to detect flaws in an in-process machine
part
Importance of NDT

15. 15
NDT methods rely upon use of electromagnetic
radiation, sound, and inherent properties of materials
(such as thermal, chemical, magnetic etc.) to examine
samples.
Common NDT Methods

16. 16
 Ultrasonic Testing
 Magnetic particle inspection
 Dye penetrant inspection/Liquid penetrant inspection
 Radiographic testing
 Eddy-current testing
 Strain Gauging.
Some of the methods used

17. 17
 Aerospace engineering
 Mechanical engineering
 Electrical engineering
 Civil engineering
 Systems engineering
 Medicines
Application Areas

18. 18
 Very short ultrasonic pulse-waves are launched into
materials to detect internal flaws.
 Used for steel and other metals and alloys, can also be
used on concrete, wood and composites (with less
resolution).
 Used in many industries including aerospace,
automotive and other transportation sectors.

19. 19
Two methods of receiving the ultrasound waveform:
 Reflection
 Through Transmission

20. 20
Principle
LEFT: A probe sends a sound wave into a test material.
There are two indications, one from the initial pulse of
the probe, and the second due to the back wall echo.
RIGHT: A defect creates a third indication and
simultaneously reduces the amplitude of the back wall
indication. The depth of the defect is determined by the
ratio D/Ep.

21. 21
Transducer Arrangement
Direct transmission Semi-direct transmission
Indirect or surface transmission
Key : Transmitter (T)
Receiver (R)

22. 22
A pulse of longitudinal vibrations is produced by a
transducer, which is held in contact with one surface of
the concrete under test. Electronic timing circuits enable
the transit time T of the pulse to be measured.
Longitudinal pulse velocity (in km/s or m/s) is given by:
v = L/T
where ,
v = Longitudinal pulse velocity
L = Path Length
T = Time taken by the pulse to traverse that length.

23. 23
(a) Results for concrete with the top 50 mm of inferior quality
(b) Results for homogeneous concrete.
Pulse velocity determination by indirect (surface) transmission.

24. 24
 Part is magnetized.
 Presence of a surface or subsurface discontinuity in the
material allows the magnetic flux to leak, since air
cannot support as much magnetic field per unit
volume as metals.
 Ferrous iron particles are then applied to the part.
 Particles will build up at the area of leakage and form
what is known as an indication.
Magnetic particle inspection

25. 25
Magnetic particle inspection

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 Penetrant may be applied to the test component by
dipping, spraying, or brushing
 After adequate penetration time, the excess
penetrant is removed, a developer is applied.
 Developer helps to draw penetrant out of the flaw
where an invisible indication becomes visible to the
inspector

27. 27
1. Section of material with a
surface-breaking crack
that is not visible to the
naked eye.
2. Penetrant is applied to the
surface.
3. Excess penetrant is
removed.
4. Developer is applied,
rendering the crack visible.

28. 28

29. 29
 Short wavelength electromagnetic radiation (high
energy photons) to penetrate various materials.
 The amount of radiation emerging from the
opposite side of the material can be detected and
measured

30. 30
 X-Ray Equipment
 Gamma Rays Equipment

31. 31
X-Ray Image of
reinforced
concrete column
X-Ray
Equipment

32. 32
Tube exhibiting no cracking Tube exhibiting light cracking
Tube exhibiting moderate cracking Tube exhibiting severe cracking

33. 33

34. 34
Uses electromagnetic induction to detect flaws in
conductive materials.

35. 35
 Variations in the phase and magnitude of these eddy
currents can be monitored using a second 'receiver' coil, or
by measuring changes to the current flowing in the primary
'excitation' coil.
 Variations in the electrical conductivity or magnetic
permeability of the test object, or the presence of any
flaws, will cause a change in eddy current and a
corresponding change in the phase and amplitude of the
measured current.

36. 36

37. 37
SCHMIDT REBOUND HAMMER TEST
Principle : It works on the principle that the rebound
of an elastic mass depends on the hardness of the
surface against which the mass impinges.
Schmidt Rebound Hammer

38. 38
A cutaway schematic view of the Schmidt rebound hammer.

39. 39
Relationship between Compressive strength of concrete and
Rebound Number

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CARBONATION DEPTH MEASUREMENT TEST
Carbonation of concrete occurs when the carbon dioxide, in the atmosphere in
the presence of moisture, reacts with hydrated cement minerals to produce
carbonates, e.g. calcium carbonate
t = (d/k)2
Where,
t = carbonation time
d = concrete cover
k = permeability
Concrete Grade Permeability
15 17
20 10
25 6
30 5
35 4
40 3.5

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Estimation of depth of Carbonation
7.2
R2(4.6x – 1.76)2 C2
Where,
y = Age of building in years
x = Water-Cement Ratio
C = Carbonation depth
R = Constant (R= αβ)
y =

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Strain Gauging
A strain gauge is a device used to measure strain on an
object. Invented by Edward E. Simmons and Arthur C.
Ruge in 1938, the most common type of strain gauge
consists of an insulating flexible backing which
supports a metallic foil pattern. The gauge is attached
to the object by a suitable adhesive, such
as cyanoacrylate. As the object is deformed, the foil is
deformed, causing its electrical resistance to change.
This resistance change, usually measured using
a Wheatstone bridge, is related to the strain by the
quantity known as the gauge factor.

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Strain Gauging

44. 44
 NDT techniques provide cost-effective and reliable analysis
under realistic conditions.
 Each NDT technique has certain capabilities and limitations
and often more than one technique is used to cover
various parts.
 Increasing availability of robotic scanners improve the
speed of testing large surfaces, hence minimizing the
testing time.

45. 45

46.  INTERNATIONAL ATOMIC ENERGY AGENCY ,VIENNA,2002 Guidebook on Non
Destructive testing of Concrete Structures .
 Source: www.wikipedia.org
 http://www.ndt-
ed.org/EducationResources/CommunityCollege/communitycollege.htm
 THE IMPORTANCE OF WELDING QUALITY CONTROL,K.M. WONG & Scarlett
YEUNG,A.E.S. Destructive & Non-Destructive Testing Ltd
 http://www.hse.gov.uk/comah/sragtech/techmeasndt.htm#CaseStudies
 http://en.wikipedia.org/wiki/Nondestructive_testing#Methods_and_techniques
 http://testex-ndt.com/from-the-field/corrosion-detected-in-pipelines-using-lfet
 Wikipedia.org and Internet.

47. End of Chapter !
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