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7/24/2019 Non Destructive Evaluation
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CE 611 Advanced Concrete
Technology
Non-Destructive Evaluation
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Outline
Introduction to condition assessment
Visual investigation
Sound based methods
Rebound and penetration techniques
Thermography and Radiography Electromagnetic techniques
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With timely inspections and repair, the service lie o the structure
can be prolonged
!eed or inspection
The racture mechanics vie"point#
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!eed or inspection
Inspections are necessary or servicing ailing inrastructure
Remaining lie can be assessed
Strategy or repair and rehabilitation can be decided depending on the
e$tent o damage and the ne" design criteria
The %ivil Engineering perspective
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Steps in condition assessment
Initial inspection and appraisal&
Inormation gathering, research and
documentary revie"&
'etailed investigations&
(ssessment o structural condition&
Reporting and recommendations&
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Initial inspection
Visual inspection Forms an integral part of anyassessment
A trained inspector canmake good use of his eye
80% of all inspectionsare visual
Even when other tests
are used visualinspections are alwaysperformed
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Visual (ids
Telescopes, )orescopes, *agniying lenses, Real+
time video, %amera
Ruler, measuring tape, crac "idth gauge -ight hammer, chipping . scraping tools
)orescopes / Rigid, le$ible, and video+assisted
-imitations o visual methods / only suracecracs, lo" reliability, needs good lighting, human
actors critical#
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)orescopes
)orescopes are industrial telescopes that give accessto closed areas& These can be o three types0
Rigid0 limited to straight line o sight1 dierent
ields o vie" can be used / either straight ahead oron the side o the instrument
2le$ible0 these are ibre optic bundles that can curveand it into enclosed areas that are unreachableusing rigid borescopes
Video+assisted0 these are le$ible borescopes "ithan attached %harged %ouple 'evice 3%%'4 camerathat can give a real time video eed&
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Visual inspection / "hat can be assessed
%oncrete construction
5atterns, location, and orientation o cracs 3"hether stressrelated or not4
Scaling and spalling
E$posed reinorcement Signs o "ater penetration
'elamination
%racs can be classiied into0 6airline / barely visible
2ine / 7.89 to 7.7: inch
*edium / 7.7: to 7.; inch
Wide /
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Visual inspection / "hat can be assessed
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'etailed investigation
Identiying and locating structural elements to establish theoverall structural orm&
Obtaining the properties o the structural materials used inthe building
'etermining the type and disposition o reinorcements inelements and connections&
-ocating deteriorated material and other deects, andidentiying their causes&
It is very much necessary to investigate the structure as it
stands1 seldom do dra"ings sho" e$actly "hat "as built,and in any case, the structure "ould have been changedduring its lietime&
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Techniques o detailed investigation
5rimarily t"o types0
3a4 Intrusive + cause minor damage to the
material or structure upon completion o
the test, and
3b4 !on+destructive
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!on+destructive techniques
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Sound+based techniques
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5rimary types o sound "aves
%ompressional . longitudinal "ave 35+"ave1 5 orprimary4
Shear . transverse "ave 3S+"ave1 S or shear4
Surace "ave 3R+"ave1 R or Rayleigh4
In a 5+"ave, the particles o the material vibrate in a direction
parallel to the "ave propagation1 perpendicular in the case o S+
"ave1 both in case o surace "aves 3elliptical particle motion4
V5> 3E.?4@&A
VS> 3
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(coustic impedance
*edium 9
*edium 7Incident sound "ave
Energy ERelected sound "ave
Energy ER
Transmitted sound "ave
Energy ET
Sound "aves traveling rom on
medium to another0ER 3F7+F94
9.3F7GF949
ET HF7F9.3F7GF949
Where Fi (coustic Impedance o
*edium I
F ?V, i&e& the product o the density o
the material and the "ave velocity
F 3in g.m9s4 or0
(ir @&H@1 Water 7&A$7@:
%oncrete C$7@:1 Steel H$7@:
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Sounding
The quality o sound produced
by =ust striing the surace o
concrete "ith a hammer can
reveal inormation about damage
Intact concrete / ringing sound
%raced concrete / drummy
sound
Other popular technique / %hain
drag
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Jltrasonic 5ulse Velocity Technique
3J5V4
!rinciple is that the speed of travel of thesound wave depends on the density andsti"ness #or modulus of elasticity$ of thematerial
From a measurement of the time taken ythe pulse to travel the dynamic modulus ofelasticity of the material can e determined
&'ect
(ransmitter
)eceiver
*
t E +v , *-t , f#E-+$
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J5V Techniques
'irect Semi+direct
Indirect
Three modes o testing
Jse o the indirect method
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J5V Scenarios
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)IS criterion or J5V
!o& 5ulse velocity obtained in directtransmission mode 3m.sec4
%ondition o concrete
7 K H&A E$cellent
9 8&A / H&A
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%haracteriNation o concrete using J5V /
results rom tests conducted at the
%onstruction *aterials -aboratory, IIT *adras
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Variation o J5V "ith stress levels in concrete
0
10
20
30
40
50
60
70
80
90
100
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
Pulse velocity (m/s)
%
ofultimate
stress
day 1
day 7
day 28
Variation o pulse
velocity "ith stress
level has been
plotted1 as the stress
gets closer to the
ultimate stress, the
pulse velocity sho"s
a sharp decline due
to the increase incracing
(pplication0 )asic material characteriNation1
assessment o damage level in structures
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Jse o indirect method
1 ! "ay 1
y # 5$7453%
&2# 0$9904
0
50
100
150
200
250
300
350
0 10 20 30 40 50 60
"ista'ce etee' tra'sducers (cm)
Pulsetime(mic
roseco'ds)
m = 5.!5" s#cm$ulse velocity % = 1&&&.!5" m#s =
1!1 m#s
'etermination o
pulse velocity byindirect method
(dvantage0 !o need or t"o+sided access
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%omparison o methods
*'direct
y # 284$78+'(%) , 2041$2
&2# 0$821
-emi!directy # 268$34+'(%) , 3355$1
&2# 0$5432
"irect
y # 272$17+'(%) , 3456$7
&2# 0$8636
0
1000
2000
3000
4000
5000
6000
0 5 10 15 20 25 30./e (days)
Pulsevelocity(m/s)
%omparison o
direct, semi+direct,and indirect
methods
( d i i d
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(ssessment o damage in cracing due to
unia$ial compression
C-clamp
LVDT
SpringRub
bersheet
Transducer
( t d i i d t
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(ssessment o damage in cracing due to
unia$ial compression
Amplitude(mV)
Transit time x 10-!sec
( t d i i d t
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(ssessment o damage in cracing due to
unia$ial compression
@ 9@ H@ :@ ;@ 7@@@&8
@&H
@&A
@&:
@&I
@&;
@&C
7&@
7&7
0-1
V"
V0
# $% ultimate l$ad
2-1
@ 9@ H@ :@ ;@ 7@@@&@
@&9
@&H
@&:
@&;
7&@
-
A
"A
0
# $% ultimate l$ad
-
( t d i i d t
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(ssessment o damage in cracing due to
unia$ial compression
0 0 &0 '0 (0 100 100
1
)
&
*
'
+
(x 10
&
0 0 &0 '0 (0 100 100
1
)
&
*
'
+x 10
&
2requency dependence
o response
!S%
6S%
( t d i i d t
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(ssessment o damage in cracing due to
unia$ial compression
@&@ @&9 @&H @&: @&; 7&@
@&@
@&9
@&H
@&:
@&;
7&@
@
7@
9@
8@
H@
A@
:@
I@
;@
,SC
SC
S$lid Line - A " A0
D$tted Line - Crac. length
Crac.Length(mm)
Relati/eAmplitude
,$rmali0ed strain
(mplitude drop is able to better
represent the increase in crac
length at all levels o strain in
both the types o concrete& This
result indicates that ultrasonicpulse velocity alone is not
suicient to characteriNe
damage& The actual ultrasonic
signal can give valuable
inormation pertaining to the
signal amplitude 3and energy4,as "ell as requency dependence
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5ulse+echo *ethod
!ulse generated on the surface is re.ectedack y any discontinuities or cracks within thematerial
/f total depth is
known acomparison ofthe travel timescan indicate the
crack location
!ulse can also e generated y an impactsource /mpactecho method
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Jse o pulse+echo
*) / *ain bang, 2E / 2la" echo, )E 3)E7and )E94 / )ac echo
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Scanning "ith pulse+echo
-inear scan (rea scan
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5ulse+echo or resh concrete
%oncrete inside mould
Steel plate (s concrete hardens, more o
the sound energy "ill get
transmitted1 in the resh state,
most o the energy "ill be
relected rom the steel+
concrete interace
5roblems / Intererence by
bleed "ater
(pplications0 'etermination
o setting and strength gain
o concrete
Technique is still in research stage1
some researchers call it the WaveRelection 2actorP *ethod
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(coustic Emission
1ound ursts emitted y growing cracks cane detected y sensors2 y careful placementof sensors e3act location can e pointed out
!rolems4 E3tremely sensitive techni5ue2only growing cracks can e detected
S l ( l i S
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Spectral (nalysis o Surace Waves
3S(SW4 Technique
)ayleigh waves #surface sound waves likein an earth5uake$ have a spectrum ofwavelengths and travel at di"erent speeds
in layered media like pavementsdepending on the sti"ness #E$(he wave spectrumcan e analysed tootain the sti"ness
pro6les
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-imitations o sound based methods
6igh attenuation o sound "aves due to thepresence o air voids in concrete1 hence,
deep deects are not easy to ind -o" requencies only can be used
resolution is compromised
Intererence in results rom the aggregatesand reinorcementheterogeneity oconcrete is a problem#
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6ardness . 5enetration
measurements
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Rebound.5enetration Tests
Schmidt rebound hammer0 *easures theelastic rebound rom the surace o a
material 3mainly used or concrete41correlated empirically to strength
Windsor probe0 Shot into the concrete at agiven orce1 depth o penetration indicateslevel o concrete strength
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Rebound hammer test
(dequate care must be taen or preparation o the surace& I the surace is rough,
or has too many bugholes, it needs to be smoothened using a grit or sandpaper
3areas near bugholes should be avoided4& In addition, the area to be investigated
should be clean& In case the concrete is covered "ith plaster, the plaster layer should
be chipped o to reveal the concrete surace or conducting the test&
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Rebound tests / some lab results
0
5
10
15
20
25
30
35
40
0 5 10 15 20 25 30 35 40 45 50
&eou'd 'umer
-tressi'co'crete(Pa)
'ata sho"s lot o
scatter
Very diicult to use itor quantitative
prediction
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6ardness tests
6ardness is the property o a material that
enables it to resist plastic deormation,
usually by penetration& 6o"ever, the termhardness may also reer to resistance to
bending, scratching, abrasion or cutting&
*easurement by0 Scratching#, Roc"ell,)rinell, Vicers, Qnoop tests
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*ohs scale
'iamond 7@
%orundum C
TopaN ;
uartN
Orthoclase32eldspar4
:
(patite A
2luorite H
%alcite 8
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Thermography and Radiography
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Thermal techniques
/) 1ource
&'ect (hermal 1can
7etection of heat loss moisture variationconcrete integrity air leakage delaminations onconcrete decks
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IR Scan
When a deect is present in the body, it "ould sho" up as acold spot "hen heat is lo"ing in"ard, and as a cold spot "hen
the heat is lo"ing out"ard&
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Radiography
Sourcerays or neutrons
&'ect )adiograph
7etect cracks in materials especially useful forpipe testing 9:0 degree scans #;A($ also possilefor 97 reconstruction2 prolems ha
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Electromagnetic techniques
&nly useful for metallic #conductive and magnetic$
elements
Eddy current
techni5ues
=agnetic particle
techni5ues7iscontinuitiescause disturances inthe applied electric
6eld2 detected y anindicator
1urface techni5ueonly
=agnetic particlesalign along cracks inthe direction of the
magnetic 6eldAlso a surfacetechni5ue
*ainly used or steel
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E* technique or reinorced concrete
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Summary
( number o non+destructive techniques are
available to assess materials and structures
Success o the technique depends on0
+ Training "ith the method
+ %alibration o the instrument3s4
+ Qno"ledge o the damage
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%auses o damage in structures
Some e$amples
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%oncrete damage + durability
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%oncrete damage / volume changes
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%oncrete damage / thermal eects
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%oncrete damage + ire
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Steel damage / corrosion, and =oint deects
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'eects in timber
)ric masonry / oundation settlement
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c so y ou d o se e e
damage