NON DESTRUCTIVE TESTING OF CONCRETE STRUCTURES PPT

NON DESTRUCTIVE TESTING OF CONCRETE STRUCTURES

PRESENTED BY CHANDAN ASHISH (1 (118/08) 18/08) FARAH NAWAZ (138/08)

INTRODUCTION Nondestructive testing (NDT) is a wide group of analysis techniques used to evaluate the properties of a material, component or  system without causing damage.

TYPES OF TESTING OF CONCRETE STRUCTURES

DESTRUCTIVE TESTING

NONDESTRUCTIVE TESTING

DESTRUCTIVE TESTING 

Stress Testing



Crash Testing

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Hardness Testing

Destructive testing of a 6-storey concrete building using a shake table

TYPICAL DEFECTS IN CONCRETE STRUCTURES

Cracks due to concrete settling

Sketch of exposed aggregate

Cracks due to differential settlement

Rusting of reinforcing bars

Effect of atmospheric conditions

Cracks due to bending and shear stresses

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 

 A cutaway schematic view of the Schmidt rebound hammer

Relationship between Compressive strength of concrete and Rebound Number 

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 15 20 25 30 35 40

Permeability 17 10 6 5 4 3.5

Estimation of depth of Carbonation 7.2 2 y= C R2(4.6x  – 1.76)2

Where, y = Age of building in years x = Water-Cement Ratio C = Carbonation depth R = Constant (R= αβ)

ULTRASONIC TESTING  – Pulse Velocity Test  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.

Transducer Arrangement

Direct transmission

Semi-direct transmission

Key : Transmitter (T) Receiver (R)

Indirect or surface transmission

Pulse velocity determination by indirect (surface) transmission.

(a) Results for concrete with the top 50 mm of inferior quality (b) Results for homogeneous concrete.

RADIOGRAPHIC TESTING

The intensity of a beam of X rays or gamma rays suffers a loss of  intensity while passing through a material. The amount of radiation lost depends on the quality of radiation, the density of the material and the thickness traversed The relationship between the intensity of photons incident and transmitted is:

I = I0 e-µx Where, I I0 µ x

= Transmitted photon intensity = Incident photon intensity = Attenuation coefficient = Thickness of object

Equipment for Radiographic Testing : X-Ray Equipment  Gamma Rays Equipment 

Principle of radiography

X-Ray Image of reinforced concrete column

X-Ray Equipment

Other Non Destructive testing Methods

Ground

Penetration Radar  Half Cell Electrical Potential Method Permeability Test Infrared Thermography

CASE STUDY : BRIDGE

Schmidt Hammer , GPR Test being conducted on a bridge   A

 

well-established and accepted application of GPR is the accurate condition assessment of bridge decks as well as other reinforced concrete structures. Infrared imaging technologies to find defects in the concrete parts of  bridges. Ultrasonic testing allows also the visualization of perpendicularly arranged reinforcement bars.

CONCLUSION

 A large range of NDT techniques are deployed for a wide variety of application in Civil Engineering. NDT techniques can be used for evaluation and inspection of both new and existing structures.  Apart from methods discussed here, they are still a constant field of research and development due to their significance.

REFERENCES



INTERNATIONAL ATOMIC ENERGY AGENCY ,VIENNA,2002 Guidebook on Non Destructive testing of Concrete Structures .

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Wikipedia.org and Internet.

THANK YOU