The role of Non-destructive Testing (NDT) for improving ...

The role of Non-destructive Testing (NDT) for improving safety and reliability in

concrete constructionMohamad Pauzi Ismail, PhD.NDT group manager,Malaysian Nuclear Agency,Bangi, 43000 Kajang.Tel: 019-3800155Fax:603-89250907www.nuclearmalaysia.gov.mywww.utmr.blogspot.compauzi @nuclearmalaysia.gov.my

http://www.utmr.blogspot.com/

Buildingfailures

9/8/2014 2International Construction Week 17-19 Sep 2014, PWTC

Bridge failures


Periksa semua jejambat -- PM arah Kementerian KerjaRaya laksana segera seluruh negaraOleh HATA WAHARI dan YULPISMAN ASLI (Utusan Online 2006)

KUALA LUMPUR 10 Feb. - Datuk Seri Abdullah Ahmad Badawi mengarahkanKementerian Kerja Raya memeriksa serta-merta semua struktur jejambat danlebuh raya bertingkat di seluruh negara.Arahan itu dikeluarkan kepada Menteri Kerja Raya, Datuk Seri S. Samy Velluyang menemui beliau di pejabatnya di Putrajaya, hari ini.Menurut Perdana Menteri, pemeriksaan tersebut perlu disegerakan dan bukanditumpukan di ibu negara sahaja.``Jabatan Kerja Raya (JKR) dan Lembaga Lebuh Raya Malaysia (LLM) perluterus membuat pemeriksaan yang kerap terhadap jalan-jalan bertingkat keranajika didapati retak atau rosak akan dapat dibaiki dengan segera.``Kalau kita terlewat mengetahui kerosakan yang berlaku dan menyebabkanjambatan rosak, runtuh serta ditutup, ini akan menimbulkan banyak masalahkepada rakyat,'' katanya.


Why we need NDT in concrete?

• accident prevention • to reduce costs • to improve product reliability • to determine acceptance to a given requirement • to give information on repair criteria.


Where Is NDT Used?

• where we need to ensure the serviceability of a specimen

• where we cannot afford the cost of a failure of the specimen because failure would be financially unacceptable or cause harm to us

• exist to prevent injury or death to the human user of the tested item


When Is NDT Used?

• NDT is used both before, during and after construction

• Using NDT "before or during construction" prevents a substandard material or part from wasting time and increasing scrap production

• Using NDT after to monitor performance after being service.


Effective NDT

In order to gain the information and obtain valid results, the following is required:

• trained and qualified personnel • a procedure for conducting the test • a system for reporting results • a standard to interpret the results.


NDT certificate holder

• www.endt.gov.my

• https://www.asnt.org/certificant

• http://www.bindt.org/Certification/PCN_Certification_Verification

129/8/2014 International Construction Week 17-19 Sep 2014, PWTC

http://www.endt.gov.my/

https://www.asnt.org/certificant

http://www.bindt.org/Certification/PCN_Certification_Verification

http://www.bindt.org/Certification/PCN_Certification_Verification

ASNT Central Certification Program (ACCP) level III


SAMM MS ISO/IEC17025 accreditation

• NDT, SIRIM

• AIROD

• SME


MIBAS MS ISO/IEC17020

• NDT, Nuklear Malaysia

• Lott inspection

• Petrotechnical Inspection

• Careion

• NDE Consultancy


MyPTP MS ISO/IEC 17043

• Nuklear Malaysia (to be applied)


Non-destructive Testing (NDT) is a test that does not impair the intended performance of the element or member under investigation

• Visual Inspection• Rebound hammer• Rebar locator• Carbonation test• Ultrasonic• Half-cell potential• Windsor probe

• Radiography• Moisture/Density Gauge• Radar• Eddy current• Thermography• Acoustic emission• etc. 20 methods in BS

NDT in Civil & Structural Engineering includes:

What is NDT?


1- Rebound hammer

NDT methods

2- Penetration resistance

3- Pull-out

4- Ultrasonic

5- Radar

6- Thermagraphy

7- Radiography

8- Acoustic emission

9- Magnetic or eddy current

10- Half-cell Potential

11- Photography

Stre

ngth

Elas

tic M

odul

us

Thic

knes

s

Cra

ck d

epth

Cra

ck w

idth

Cra

ck d

istri

butio

n

Cra

ck d

evel

opm

ent

Hon

eyco

mbi

ng, v

oids

Lam

inat

ion

Bar

loca

tion

Bar s

ize

Bar c

orro

sion

Item

s


Strength

Items

Elastic Modulus

Deformation

Crack

Defect

Rebar

Thickness

Build

ing

Tunn

el

Port

Dam

s

Foun

datio

n

Brid

gesStru

ctur

e

Distribution

Width

Depth

Delamination

Honeycombing, voids

Backwall voids

Location, size

Corrosion

very important important


Inspection Program

Country Structures USA Singapore Japan M’sia

Building N/K every 5yr as request

every 10y

Bridge every 2 yr N/K

every yr (visual)

every year (visual)


Code, standard availability

Items Mechanical constr.

Civil constr.

1.Test method 2.Acceptance criteria 3.Personnel qualification

?? x


Building InspectionFlow chart Record

SECOND SURVEY

Evaluation

Prelimanary survey

History, drawing

Visual inspection

Yes (Grade III)

No

Carbonation Test

Rebar corrosion Repair if Grade III & IV

Record

THIRD SURVEY if Grade II, III & IV

Crack surveyRepair if Grade II

& III and crack not growing

THIRD SURVEY if crack is growing

Water leaking Repair if Grade III & IV

THIRD SURVEY if Grade III & IV

Concrete strength

Repair if Grade II & III

THIRD SURVEY if Grade II & III

Large Defelection Repair if Grade

III & IVTHIRD SURVEY if Grade III & IV

Surface Deterioration

Repair if Grade II & III

THIRD SURVEY if Grade II & III

Estimate remaining life


Bridge Inspection Flow chart

NECESSARY OF REPAIR

CONDITION OF BASE PLATE

ROUTINE SURVEY

REMARKABLE

DETAILED SURVEY

DECISION ON NECESSARY OF SURVEY

INVESTIGATION

DECISION ON NECESSARY OF SURVEY

CHECK ON DESIGN

RECORDS(DATA BANK)

ADDITIONAL SURVEY

YES

NO

NO

NO

RECORD

FOR REFERENCE

2 years interval

VISUAL INSPECTION

• The first survey• Observe any surface

discontinuities• Visual features may be related

to workmanship, structural serviceability & deterioration

Typical defects in building


Typical defects in bridge

Honeycomb

Water leakage

spalling

cracks

Exposed barExposed bar


Crack mapping/density


Acceptance criteria (building)


Acceptance criteria (building) BS8110‐2‐1985

• 3.2.4 Excessive cracking

• 3.2.4.1 Appearance. For members that are visible, cracking should be kept within reasonable bounds by

• attention to detail. As a guide the calculated maximum crack width should not exceed 0.3 mm.

• 3.2.4.2 Corrosion. For members in aggressive environments, the calculated maximum crack widths should

• not exceed 0.3 mm.

• 3.2.4.3 Loss of performance. Where cracking may impair the performance of the structure,

• e.g. watertightness, limits other than those given in 3.2.4.1 and 3.2.4.2 may be appropriate.

• For prestressed members, limiting crack widths are specified in section 2 of BS 8110‐1:1997


Acceptance criteria (building) BS8110‐1‐1985

• 2.2.3.4.2 Prestressed concrete

• In the assessment of the likely behaviour of a prestressed concrete structure or element the amount of flexural tensile stress determines its class, as follows:

• class 1: no flexural tensile stresses;

• class 2: flexural tensile stresses but no visible cracking;

• class 3: flexural tensile stresses but surface width of cracks not exceeding 0.1 mm for members in very aggressive environments (e.g. exposure to sea or moorland water) and not exceeding 0.2 mm for all other members


Acceptance criteria (bridge)


BAR LOCATOR

• Electromagnetic covermeter or Radar technique• Measure cover thickness• Location of the reinforcement bar• Accuracy:


Ground Penetrating Radar (GPR)

• Uses electromagnetic waves to penetrate concrete

• Propagation dependent on dielectric constant and electrical conductivity of media

NEUTRALIZATION/CARBONATION TEST/pH TEST

A purple‐red coloration will be observed in the area highly alkaline concrete, and no coloration will

appear in carbonated area

CARBONATION TEST (cont)

• Test concrete should be treated immediately after sample has been cut or broken from concrete member.

• The carbonated part ‐ will show no colouration. The good part of highly alkline ‐ red‐purple colouration.

• Alternative method: by drilling into concrete member and drill powder may be sprayed by the indicator‐observe change of colouration


REBOUND HAMMER

• basically a surface hardness test

• can be correlated with concrete strength

• estimation error ~ 30%

Correction for age effect


ULTRASONIC METHOD

• Pulse velocity

• Attenuation

• Phase change

• Monitor mixing materials, concrete uniformity

• Detect void or honeycombs

• Measure crack depth, slab thickness

• Depth of damage

• Estimate strength

Ultrasonic Measurements in Concrete

• Frequency used: 25 and 250 kHz, i.e. wavelengths range from 200 mm to 10 mm

• Possible to test samples thickness of up to 13 m at low frequency

• Measurements usually involve determination of the speed of sound


Testing methods

• Resonance for determine Young Modulus

• Through Transmission pulse method

• Pulse echo method


Resonance Equipment


Pulse echo reflection


Ultrasonic tomography

9/8/2014 International Construction Week 17-19 Sep 2014, PWTC 45

Panel hadapan – Imej tomografi Panel belakang - transduser

Pemeriksaan terowong kereta api Imej tomografi yang dihasilkan

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http://www.acsys.ru/eng/production/detail/a1040-mira/

Pulse Transmission

• Direct technique

• Diagonal (semi‐direct)

• Surface

(a) (b)

(c)International Construction Week 17-19 Sep

2014, PWTC9/8/2014 46

Strength Estimation


Flaw Detection in Concrete

• presence of internal defects in a sample of concrete gives rise to a decrease in amplitude of the received signal

• Surface cracks are comparatively easy to evaluate using BS or phase reversal

)()(

21

22

22

21

21

22

tttatad

−−

=


Acceptance criteria

Pulse velocity (m/s) General Condition

Above 45753660 – 45753050 – 36602135 – 3050below 2135

ExcellentGenerally goodQuestionable

Generally poorVery poor

Penetration Test (Windsor probe)

• based on depth of penetration of probe into concrete.

• This can be directly correlated to compressive strength of concrete.


Radiography

• X‐rays or gamma‐rays penetrates through concrete samples, and image of change in thickness or density collected by the photographic film.

• The variations of intensity detected correspond to internal structures of the concrete sample.

• Suitable for study on aggregates arrangement, present of voids, internal cracks, segregation, honey‐combed and reinforcement bar condition and position.


Radiation sources

• Iridium, Ir‐192 (206‐612 keV)– Half life= 74 days, Output = 0.48– Penetration: 25mm~250mm concrete

• Cobalt, Co‐60 (1173‐1333 keV)– Half life= 1925 days, Output =1.30– Penetration: 125mm~500mm concrete

• Linac/Betatron 8MeV X‐rays– penetrate 500mm~1600mm


Typical Exposure chart


Typical Radiographs from concrete• Radiographic image of

1200 mm thick concrete using a 7.5 MeV Betatron and Agfa Structurix DPS image plate. The three holes in the centre have a diameter of 20 mm and depth 15, 20 and 40 mm (from top to bottom)


Example of radiographic image of void and bar in concrete. SFD: 500mm, concrete thickness: 150mm, source: Ir-192, exposure: 4 Ci-hr, film: Agfa D7


Advantage and disadvantage of RT

• High energy radiography has been found to be reliable NDT method for locating pre‐stressed cable ducts, determine the existence and size of voids in the grout filler inside the ducts, and also to enable inspection of the cables themselves.

• Method has not been fully exploited on site, possibly because of radiation safety considerations and possibly because of portability and cost


Gamma/Neutron Gauge

• Use to check degree of concrete compaction and moisture content


IR Thermography

• Application of IR could be either using passive or active technique

• Passive technique ‐monitor heat distribution existing in the system whereby a ‘hot spot’ will be indicated as a possible defect.

• Active technique ‐monitoring will be carried out after building heated by sun


Typical Thermographs compared to photographs

Cold area

Cold area


CONCLUSION

• NDT has been applied successfully in mechanical engineering

• In Civil construction NDT is used as detail investigation as a result of sign of deterioration found during visual survey.

• NDT instrument is cheap, simple and portable.

• NDT may replace destructive testing


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