non destructive evaluation

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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Amplitude(mV)

Transit time x 10-!sec

( t d i i d t


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@ 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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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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@&@ @&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

non destructive evaluation

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