NON –DESTRUCTIVE TESTING OF CONCRETE STRUCTURES

Guided By

Asst.Prof. P.M.Ravindra

Submitted By

Shivakumar.Chitkoti

INTRODUCTION Non-destructive methods have been in used for Non-destructive methods have been in used for

about about four decades. In this period the four decades. In this period the

development has taken development has taken place to such an place to such an extent extent

that it is now considered as that it is now considered as powerful method for powerful method for

evaluating existing concrete evaluating existing concrete structures with regard to structures with regard to

there strength and there strength and durability durability apart from apart from

assessment and control of assessment and control of quality quality of of

hardened concrete. hardened concrete.

In certain cases, the investigation of crack depth, In certain cases, the investigation of crack depth,

micro cracks and progressive deterioration micro cracks and progressive deterioration

Here we shall mainly highlight on the principle Here we shall mainly highlight on the principle

and working of the following non-and working of the following non-

destructive destructive testing equipments.testing equipments.

1)1)Sclerometer-test Sclerometer-test

2)2)Seismic non-destructive testSeismic non-destructive test

3)3)Laser ultrasonic-test andLaser ultrasonic-test and

4)4)Structure scan opticalStructure scan optical

NDT as the ability to determine the NDT as the ability to determine the

strength strength and durability of critical construction and durability of critical construction

without without damaging them and the test can be damaging them and the test can be

carried carried on site.on site.

NEED FOR TESTINGNEED FOR TESTING

Modern non-destructive test are Modern non-destructive test are represented in this report which mainly represented in this report which mainly deals with determination of compressive deals with determination of compressive strength of concrete, presence of any voids strength of concrete, presence of any voids or cracks in concrete structure, and about or cracks in concrete structure, and about corrosion of steel.corrosion of steel.

Assessment of structural integrity or safety Assessment of structural integrity or safety following material deterioration or following material deterioration or structural damage such as caused by fire, structural damage such as caused by fire, blast, fatigue or overload.blast, fatigue or overload.

Monitoring long-term changes in material Monitoring long-term changes in material properties and structural performance.properties and structural performance.

1. SCLEROMETER TEST (TECHNIQUE ON STRENGTH

ASSISSMENT OF CONCRETE STRUCTURES).

NDT METHODSNDT METHODS

MATERIALS USED FOR TEST :

Ordinary Portland cement

Well graded fine and coarse aggregate

Identified silica fume (dry powder)

All tests were done on standard cubes of

dimensions 150mmX150mmX150mm for each

of mix in each series.

Cubes were than cured in water and were removed

at about 6 hours before the test performed in

order to have necessary preparation.

Tests were done on 3rd, 7th, 14th, 28th and on 58th

day of curing.

Cubes are tested one by using sclerometer

equipment and other by universal testing machine.

TEST PROCEDURE :TEST PROCEDURE :

Place sclerometer perpendicular to the test surface

by resting on its three points firmly and evenly.

Sufficient amount of pressure to be imposed on

sclerometer at the time of test so that when the

hook is released the sclerometer does not get

displace or move.

Fig:(1.a)

Fig ( 1.b): Line pattern for testing

As soon as the hook release button is pressed, the

block head will strike the surface of the cube and

the compressive strength at that point of

contact will be displayed on electronic block

indicator as shown in fig(1.a):

Hence for finding the compressive strength of the

entire cube, stable pattern of testing is done, as

explained below.

Mark six lines perpendicular to each other on each

face of cube and than perform the test 15 times in

circular form at each point on the surface of the

cube, as shown below in Fig (1.b):

After completion of test press the average button,

by which the compressive test of the entire cube

will be displayed on the electronic hook display.

For all the mentioned mix design and for all

mentioned days of curing, perform both sclerometer

test and test on universal compression testing

machine and plot the graph for their compressive

strength achieved in different days separately.

On comparing both the graph drawn one from

sclerometer test and another from universal testing

machine, we can see that, for every mentioned mix

design and for different days of curing, the values of

compression test obtained by sclerometer test are

almost (95%) same as that were obtained from

universal testing machines, as shown in below graph:

(1)a

Graph (1.a): Graphs showing the Compressive strength comparison

2. LASER ULTRASONIC TEST

Laser ultrasonic is a unique technology that can

detect the internal defects in the concrete structures,

based on its velocity dispersion theory.

INSTRUMENT DETAILS :

TEA CO2 laser ( Transversely exited atmospheric pressure laser) of wave length 10.6mm

Reflecting mirror ZnSe lens of focal length 200mm Laser Doppler vibrometer Oscilloscope and pc.

The experimental setup is shown in fig ( 2.a):

fig ( 2.a):

TEST PROCEDURE :

As soon as the laser beam is produced, it is made to

reflect by using mirror, this reflected laser beam is than

passed in ZnSe lens and their after it is made to strike on

the surface of the concrete specimen. This working

process is explained in fig :( 3b) as shown below.

Fig :( 2.b) Working process

When the beam strike the surface of specimen, the

temperature at the point of contact will goes on

increasing.

Because of increase in this temperature, thermal

strain in concrete specimen will also increase, as a

result the ultrasonic waves will get generated and

these waves are detected by the laser Doppler

vibrometer at the receiving point.

Like wise at different intervals by shifting the

receiving point by 10cm-20cm throughout the length

of specimen, the generated wave forms are detected

and are passed to digital oscilloscope were

averaging of different wave forms are made and than

stored in pc.

Graph :( 2.a) Vibration velocity vs Time

3.STRUCTURE SCAN OPTICAL

As the name indicates, it will scan the inner

portion of the concrete structures and it will give the

3D-Photos for analyzing.

INSTRUMENT DETAILS :

Optical mat

Optical antenna

Data collection pad and data storing device as

shown below in fig ( 3.a)

Fig (3.a) Structure scan optical instrument.

TEST PROCEDURE :

Place the optical mat on the surface of the concrete

structure which has to be scanned.

Now switch on the instrument button and move it on

the entire mat which is connected to high resolution

antenna of 1.6 GHz by which even very smaller

targets in the concrete can be scanned.

After scanning is completed, we can view and

interpret the data results.

Some of the photos taken from this test are as shown

below in fig ( 3.b):

On watching such kind of photos, one can clearly

identify any type of defects like voids, cracks or

corrosion of steel etc, can be identified easily.

This entire test process will take only 5mins of

time for completion.

CONCLUSIONS:CONCLUSIONS: Although non-destructive tests are relatively simple to Although non-destructive tests are relatively simple to

perform, the analysis and interpretation of the test data perform, the analysis and interpretation of the test data

are not so easy because concrete is a complex material. are not so easy because concrete is a complex material.

The user is therefore cautioned that interpretation of the The user is therefore cautioned that interpretation of the

test data must always be carried out by specialists in test data must always be carried out by specialists in

this this field rather than by technicians performing the tests.field rather than by technicians performing the tests.

The use of non-destructive tests leads increase the The use of non-destructive tests leads increase the

safety safety and allows better scheduling of construction, and allows better scheduling of construction,

thus making thus making it possible to progress faster & more it possible to progress faster & more

economical.economical.

From above all discussed tests that we have From above all discussed tests that we have

made made from that we can finally conclude that, from that we can finally conclude that,

by making by making use of these modern non-destructive use of these modern non-destructive

tests of concrete tests of concrete equipments its not only becomes equipments its not only becomes

economical, but also economical, but also gives unique results with gives unique results with

very less amount of time, very less amount of time, when compared to when compared to

universal testing machines. universal testing machines.

REFFERANCES

Sclerometer-test test John.H.Bungey, surrey university press.USA. Aictin pc, Mehta pk ‘ACI Material journal’, volume

87. Said Irvani, Mechanical properties of high-

performance concrete. ACI Material journal, volume 93.

Seismic test Zhao.H, Guo.T and sun, multi-phase engineering

seismic prospecting. Laser ultrasonic test

Davis.S.J, laser-generated ultrasound: Its properties.

Structurescan optical www.structurescan.com