NON DESTRUCTIVE TESTING OF CONCRETE STRUCTURES

PRESENTED BY -

CHANDAN ASHISH (118/08)

FARAH NAWAZ (138/08)

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

INTRODUCTION

Non Destructive Testing

TYPES OF TESTING OF CONCRETE STRUCTURES

DESTRUCTIVE TESTING

NON-DESTRUCTIVE

TESTING

DESTRUCTIVE TESTING

Stress Testing Crash Testing 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 conditionsCracks 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 Permeability 15 17 20 10 25 6 30 5 35 4 40 3.5

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 =

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

Indirect or surface transmission

Key : Transmitter (T) Receiver (R)

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

Pulse velocity determination by indirect (surface) transmission.

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 = Transmitted photon intensity I0 = Incident photon intensity µ = Attenuation coefficient x = 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 RadarHalf Cell Electrical Potential MethodPermeability TestInfrared 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 .

Wikipedia.org and Internet.

THANK YOU