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