k 6 pbasheer

The Queens University of Belfast, Northern Ireland, U.K.The Queens University of Belfast, Northern Ireland, U.K.

ICDS12, Lisbon, Portugal: 31 May - 1 June 2012ICDS12, Lisbon, Portugal: 31 May - 1 June 2012

PAM Basheer, S Srinivasan and S NanukuttanQueens University Belfast, Northern Ireland, UK

WJ McCarter and TM ChrispHeriot-Watt University Edinburgh, Scotland, UK

T Sun and KTV GrattanCity University London, England, UK

PAM Basheer, S Srinivasan and S NanukuttanQueens University Belfast, Northern Ireland, UK

WJ McCarter and TM ChrispHeriot-Watt University Edinburgh, Scotland, UK

T Sun and KTV GrattanCity University London, England, UK

Novel Sensors for Monitoring the Durability of Concrete StructuresNovel Sensors for Monitoring the Durability of Concrete Structures


Outline of the PresentationOutline of the Presentation

Need for Monitoring Structural Concrete for Durability and Structural Integrity

What We Should Monitor?Fibre Optic Sensors and ResultsElectrical Sensors and ResultsConcluding Remarks



ICDS12 International Conference DURABLE STRUCTURES: from construction to rehabilitation LNEC Lisbon Portugal 31 May - 1 June 2012

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Manifestation of Lack of DurabilityManifestation of Lack of Durability

Bridge of Lions, Florida


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Manifestation of Lack of DurabilityManifestation of Lack of Durability

Canada, 2006: 5 people were killed in a bridge collapse caused by road salt induced corrosion

Canada, 2006: 5 people were killed in a bridge collapse caused by road salt induced corrosion


0 5 10 15 20 25 30 35 40 450

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Depth from surface (mm)

Chl

orid

e co

ncen

tratio

n (%

mas

s of

con

cret

e)

Reinforcement level

Critical concentration

1 year 5 years 10 years

Chloride Profiles in Long-term ExposuresChloride Profiles in Long-term Exposures


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Role of Monitoring SystemsRole of Monitoring SystemsD

egre

e of

Det

erio

ratio

nD

egre

e of

Det

erio

ratio

n

TimeTime Service lifeService life

FINAL STAGEFINAL STAGE

Initiation periodInitiation period Active periodActive period

Initiation ofInitiation ofdeteriorationdeterioration

PropagationPropagationof deteriorationof deterioration

Changes ofChanges ofmaterial propertiesmaterial properties

t0 tf


Role of In Situ MonitoringRole of In Situ Monitoring

Duration of exposure (years)Duration of exposure (years)

Perf

orm

ance

in m

easu

rabl

e te

rms

Perf

orm

ance

in m

easu

rabl

e te

rms

1

2

3

Minimum acceptable levelMinimum acceptable level

ServiceServiceLifeLife

Intermittent Repair/maintenanceIntermittent Repair/maintenance


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Objectives of MonitoringObjectives of Monitoring

To specify performance of structures in measurable properties

To control the quality during construction To investigate the current condition To diagnose the causes and extent of defects

or deterioration To select an appropriate solution & quantify the

effectiveness of remedial action

To predict the service life

To specify performance of structures in measurable properties

To control the quality during construction To investigate the current condition To diagnose the causes and extent of defects

or deterioration To select an appropriate solution & quantify the

effectiveness of remedial action

To predict the service life








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Common Causes of Deterioration of ConcreteCommon Causes of Deterioration of Concrete

10%

9%

4%

17%

33%

5%

10%

5%7%

Abrasion and erosion

Alkali-aggregate reaction

Chemical attack

Corrosion (Carbonation)

Corrosion (Externalchlorides)Corrosion (In-builtchlorides)Freezing/Thawing

Shrinkage and settlement

Other (Infrequent)


Significance of In Situ Testing of Concrete CoverSignificance of In Situ Testing of Concrete Cover

H2O CO2 O2 Cl- SO3-

Ingress from the environment

Sorptivity Permeability DiffusivitySorptivity Permeability Diffusivity

Cover ConcreteCover ConcreteStrength

Abrasion resistanceStrength

Abrasion resistance

Depth fromthe surfaceDepth fromthe surface

PorosityPermeation properties

PorosityPermeation properties

Variation of propertiesVariation of properties


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What Do We Monitor in the Context of Corrosion?What Do We Monitor in the Context of Corrosion?

x

CO2

pH13

7

H2O

Cl-

x

Cl-

100%

0%

20000 ppm

200 ppm

Moisturecontent

Moisturecontent

Carbonation(pH)

Carbonation(pH)

Chloride IngressChloride Ingress


Surface is the Achilles heel of concrete !Surface is the Achilles heel of concrete !

Location of SensorsLocation of Sensors


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Sensor Systems for SHM Developed by the UK TeamSensor Systems for SHM Developed by the UK Team

Fibre Optic Sensors Temperature RH pH Chlorides Strain

Fibre Optic Sensors Temperature RH pH Chlorides Strain

Electrical Resistivity Sensors Moisture movement Chloride ingress Carbonation Corrosion

Electrical Resistivity Sensors Moisture movement Chloride ingress Carbonation Corrosion








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Humidity SensorHumidity Sensor

Humidity sensorHumidity sensor

Temp. sensor

Polycarbonate tube1cm dia., 20cm longLeast cavity vol. 30mm3

Polycarbonate tube1cm dia., 20cm longLeast cavity vol. 30mm3


New application being developed for FBG-based RH sensors

Monitoring of moisture ingression in concrete

Corrosion warning sensor for steel reinforcement in concrete structures

New application being developed for FBG-based RH sensors

Monitoring of moisture ingression in concrete

Corrosion warning sensor for steel reinforcement in concrete structures

FBG RH Sensor

Water Bath

Concrete samples of different water/cement ratio

Testing of Humidity SensorsTesting of Humidity Sensors


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Testing of Humidity SensorTesting of Humidity Sensor

Response of cylindrical sample with sensor in centre to gradual penetration of water to reach sensor

Response rapid for the long time scales involved in civil engineering monitoring

Sensor robustness being evaluated

Response of cylindrical sample with sensor in centre to gradual penetration of water to reach sensor

Response rapid for the long time scales involved in civil engineering monitoring

Sensor robustness being evaluated

Concrete Sample

FBG RH Sensor

1534.85

1534.90

1534.95

1535.00

1535.05

1535.10

1535.15

1535.20

1535.25

0 50 100 150 200 250 300 350

Time (min)

Bra

gg W

avel

engt

h (n

m)

5

25

45

65

85

105

Rel

ativ

e H

umid

ity (%

RH

)

Water/Cement Ratio: 0.7


W/Cratio

Cement (kg) Coarse Agg. (kg)

Fine Agg.(kg)

Water(kg)

0.55 404 1211.55 605.76 222.11

Probe embedded at 20 mm from surface Probe embedded at 20 mm from surface

Mix DetailsMix Details

Embedding RH Probe in ConcreteEmbedding RH Probe in Concrete


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Monitoring of Fresh Concrete Monitoring of Fresh Concrete

TemperatureTemperature Relative Humidity Relative Humidity

Temperature and RH MonitoringTemperature and RH Monitoring

0

5

10

15

20

25

30

35

0 10 20 30 40Time (Hrs)

Tem

pera

ture

(C

)

0

20

40

60

80

100

0 10 20 30 40Time (Hrs)

Rel

ativ

e H

umid

ity (%

)


FOS-RH probe (3cm)

Capacitance based RH probe (3cm)

Capillary Rise Test Set UpCapillary Rise Test Set Up

Water level

To data logging system

Climatic Cabinet

20C/65% RH


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RH and Temperature Variations in Capillary Rise TestRH and Temperature Variations in Capillary Rise Test

RH

Temperature

0

10

20

30

40

50

60

70

80

90

100

0 100 200 300 400 500 600 700 800 900 1000Time (min)

Rel

ativ

e H

umid

ity (%

RH

)

FOS RH probe

Capacitance RH probe

0

5

10

15

20

25

30

35

40

45

50

0 100 200 300 400 500 600 700 800 900 1000Time (mins)

Tem

pera

rue

(C

)

FOS RH probe

Capacitance RH probe


RH and Temperature Variations During DryingRH and Temperature Variations During Drying

RH

Temperature

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 60 70Time (hrs)

Rel

ativ

e H

umid

ity (%

RH

)

FOS RH probeCapacitance RH probe

0

5

10

15

20

25

30

35

40

45

50

0 10 20 30 40 50 60 70Time (hrs)

Tem

pera

ture

(C

)

FOS RH probeCapacitance RH probe


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Fibre Optic pH SensorsFibre Optic pH Sensors

Reactive tip

Permeable disc impregnated with reactive chemical

Sol-gel based

25mm

Reactive tip

Permeable disc impregnated with reactive chemical

Sol-gel based

25mm


Measurement Set Up For pH SensingMeasurement Set Up For pH Sensing

Commercially available spectrometer

Tungsten halogen broadband light source

Bifurcated fibre optic cable


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Placement of pH FOS in ConcretePlacement of pH FOS in Concrete

Probes prepared by covering with moisture permeable layer before placing in mould

Probes prepared by covering with moisture permeable layer before placing in mould


9.6

9.8

10

10.2

10.4

10.6

10.8

11

0 20 40 60 80 100 120 140

Time (seconds)

pH

pH of Cement Mortar Measured Using Embedded FOS pH ProbepH of Cement Mortar Measured Using Embedded FOS pH Probe


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pH Measured Using FOS pH Probe in Hardened ConcretepH Measured Using FOS pH Probe in Hardened Concrete


Measurement of Carbonation using pH SensorsMeasurement of Carbonation using pH Sensors

Phenolphthalein test(Depth of carbonation

5mm

6mm dia and 5 and 10mm deep holes drilled in

samples and FOS Sensors used to measure the pH

Sol-gel Probe

9

9.510

10.5

11

11.512

12.5

13

5 10Depth (mm)

pH

Sol-Gel

pH paper


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Comparison of FoS pH Sensor with Glass Electrode pH MeterComparison of FoS pH Sensor with Glass Electrode pH Meter

Measurement of pH change in concrete sample with time (v standard glass electrode pH meter)

Accelerated carbonation over a period of 6 weeks

Good agreement between the measurements

Measurement of pH change in concrete sample with time (v standard glass electrode pH meter)

Accelerated carbonation over a period of 6 weeks

Good agreement between the measurements 9.00

9.50

10.00

10.50

11.00

11.50

12.00

12.50

13.00

9.00 9.50 10.00 10.50 11.00 11.50 12.00 12.50 13.00

SG1vsstandard

Week0Week2Week4Week6BestfittodataLinear(Bestfittodata)

Graph y = x

pH change at different time plotted


Fibre Optic Chloride SensorFibre Optic Chloride Sensor

Reactions giving calorimetric changes with chloridesReactions giving calorimetric changes with chlorides

Sol-gel based chloride sensor probe

Sol-gel based chloride sensor probe

Calibration of chloride sensor

Calibration of chloride sensor


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Fibre optic chloride sensorFibre optic chloride sensor

Reactions giving calorimetric changes with chloridesReactions giving calorimetric changes with chlorides

Fluorescent dyes, Silver salts AgNO3 , Ag2CrO4 ,fluorescein

Encapsulation in sol-gel materials

Miniature spectrometer in the visible range of spectrum used

Fluorescent dyes, Silver salts AgNO3 , Ag2CrO4 ,fluorescein

Encapsulation in sol-gel materials

Miniature spectrometer in the visible range of spectrum used

Chloride sensor probeChloride sensor probe


Fibre Optic Chloride Sensor and Calibrations at pH 12Fibre Optic Chloride Sensor and Calibrations at pH 12

FluoresceinFluorescein

AgNO3AgNO3 Ag2CrO4Ag2CrO4


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New Fibre Optic Chloride & pH SensorNew Fibre Optic Chloride & pH Sensor

New design being patented

Long Period Grating based sensor for pH and chloride monitoring

Testing of the sensors in progress

New design being patented

Long Period Grating based sensor for pH and chloride monitoring

Testing of the sensors in progress








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Types of Electrical SensorsTypes of Electrical Sensors

Reference Electrode Electrochemical potential sensors Corrosion rate sensors Macro cell sensors Time-to-corrosion and critical depth sensors Concrete resistance sensors Oxygen (reduction) sensors Relative humidity sensors Temperature sensors

Reference Electrode Electrochemical potential sensors Corrosion rate sensors Macro cell sensors Time-to-corrosion and critical depth sensors Concrete resistance sensors Oxygen (reduction) sensors Relative humidity sensors Temperature sensors


Schematic of Some SensorsSchematic of Some Sensors

Voltmeter

RebarReferenceelectrode

Concrete

Potentiostat

RebarCounter

electrode

Concrete

Referenceelectrode

PotentialMeasurement

Corrosion RateMeasurement

Potentiostat

Counterelectrode

Concrete

Referenceelectrode

Oxygen ReductionMeasurement


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Electrical SensorsElectrical Sensors

CorroWatch CorroWatch APM 303 APM 303 BRE (Sergi)BRE (Sergi)


Electrical SensorsElectrical Sensors

Electrode Array(McCarter)

Electrode Array(McCarter)

Anodic Ladder(Schiel)

Anodic Ladder(Schiel)


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Macro-cell Current Due to Corrosion of Steel in ConcreteMacro-cell Current Due to Corrosion of Steel in Concrete


Anode Ladder Arrangement No. 1 to Monitor Corrosion InitiationAnode Ladder Arrangement No. 1 to Monitor Corrosion Initiation


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Anode Ladder Arrangement No. 2 to Monitor Corrosion InitiationAnode Ladder Arrangement No. 2 to Monitor Corrosion Initiation


Anode Ladder Installation Details: Side and Top ViewsAnode Ladder Installation Details: Side and Top Views


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Miniature, Multiple Electrode ArraysMiniature, Multiple Electrode Arrays

Resistance varies with the advance of drying/wetting front and chloride frontResistance varies with the advance of drying/wetting front and chloride front


Spread of electric field between embedded

electrodes

Variation of electrical resistance ratio across the electrodes due

to advancing water front

33

22

11

Direction of movement of water

Electrodes

Electric field

Resistance measurement- effect depends on what causes change of resistance

Covercrete Electrode ArrayCovercrete Electrode Array


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Electrical Resistance SensorsElectrical Resistance Sensors

For New StructuresFor New StructuresFor ExistingStructures

For ExistingStructures


Electrical Resistance SensorsElectrical Resistance Sensors

For New StructuresFor New Structures

Corrosion monitoring

sensors


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Wireless Monitoring of StructuresWireless Monitoring of Structures

Multiplex UnitMultiplex UnitData Logger

& Power Supply

Data Logger&

Power Supply

Solar PanelSolar Panel


Dornoch Test Site, ScotlandDornoch Test Site, Scotland


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Samples in Position and On-site MonitoringSamples in Position and On-site Monitoring


Details of Site Investigation at DornochDetails of Site Investigation at Dornoch

1234

56

7 8

MeanLowtide

SprayXS1

SplashXS3

MidtideRiprap

MeanHightideXS3

XS2

High

Mid

Low

OPC: CEMI-42.5NGGBS: CEMIII/A-42.5NPFA: CEMII/B-V-42.5N


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Results from High Level Location, XS1Results from High Level Location, XS1

0

0.5

1.0

1.5

2.0

0 100 200 300 400 500

5mm10mm15mm30mm50mm

(c) PFA

Time (days)

NC

0

0.5

1.0

1.5

2.0

0 100 200 300 400 500

5mm10mm15mm30mm50mm

(a) OPC

Time (days)

NC

0

0.5

1.0

1.5

2.0

0 100 200 300 400 500

5mm10mm15mm30mm50mm

(b) GGBS

Time (days)

NC


Results from Low Level Location, XS2Results from Low Level Location, XS2

0

1

2

3

4

0 200 400 600 800

5mm10mm15mm30mm50mm

OPC

Time (days)

Nc


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NPL Bridge TestingNPL Bridge Testing

Dismantled foot bridge at NPL

used for testing purposes

Non-destructive testing to identify

cracks and delamination in deck

slab

Monitor electrical resistivity of the

pier and the deck


NPL Bridge : Installation of SensorNPL Bridge : Installation of Sensor

ER sensor

Drilling hole

Sensor installed

Remote monitoring


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NPL Bridge : Data for 100 daysNPL Bridge : Data for 100 days

00.10.20.30.40.50.60.70.80.9

1

0.00 20.00 40.00 60.00 80.00 100.00

Ele

ctric

al R

esis

tanc

e R

atio

(Rt/R

o)

Time (days)

Pier

Deck slab

Microclimatic variations need to be taken into account in service life predictions


Models for Predicting the PerformanceModels for Predicting the Performance

Service Life Models

HymostrutiC

StadiumNIST

Life365Stadium

NISTClinConcDuracrete


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SHM and Service Life ModelsSHM and Service Life Models

Service life(1) How reliable are models for predicting the performance

parameter and its influence on service life prediction?(2) How can data from SHM be incorporated in refining

predictions using models?

Duration of Exposure

Changes of performance parameter

Perf

orm

ance

Spe

cifie

d FINAL STAGE

tf

Spread of performance


Prediction of Performance Using ClinCon ModelPrediction of Performance Using ClinCon Model

Chl

orid

e C

onte

nt (%

wt c

onc)

0.0

0.2

0.4

0.6

0.8

0

1

2

3

4

5

6

0 20 40 60 80 100

Depth [mm]

Cl [

% b

y w

t of b

inde

r] Min x c for tL with 95% confidence

After 1 year

0

1

2

3

4

5

6

7

0 20 40 60 80 100

Depth [mm]

Cl [

% b

y w

t of b

inde

r] Min x c for t L with 95% confidence

0

1

2

3

4

5

6

7

8

0 20 40 60 80 100

Cl [

% b

y w

t of b

inde

r]

Depth [mm]

Min xc for tL with 95% confidence

After 7 years

After 50 years


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Role of SHM on Predicting the PerformanceRole of SHM on Predicting the Performance

Water/binder, binder content, type of binder, quality of finish

Details of exposure environment

Design

Data from monitoring units


In service

Transport properties, overall condition


In service

BS 8500 & Weather stations

Using monitoring systems

By testing/condition assessment








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Compare performance

YES NO

No

Carry out NDTsYES

Are theresults

satisfactory?

YES

Is theperformancesatisfactory?

NoYES

NO

Record the datafor future use

Durable Structures!

Do youhave embedded

sensors?

Have youdone NDTs?

Record the datafor future use

Take appropriateremedial action

Flowchart to Ensure Durable StructuresFlowchart to Ensure Durable Structures


Assessment of Service Life from In situ MonitoringAssessment of Service Life from In situ Monitoring

Service lifeDuration of Exposure

Perf

orm

ance

Spe

cifie

d FINAL STAGE

tf

(1) Useful for early identification of potential problems and addressing them

(2) Decide on time for planned maintenance and repair, or estimate service life

Early Urgent Intervention Required

Plan for carrying out intermittent repair

Structure can no longer be safely used


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Concluding RemarksConcluding Remarks

All sensors were functionally viable

Fibre optic sensor longevity in concrete needs to be studied

Their long-term performance is unknown

Their usefulness for service life prediction needs to be established

All sensors were functionally viable

Fibre optic sensor longevity in concrete needs to be studied

Their long-term performance is unknown

Their usefulness for service life prediction needs to be established


Novel Sensors for Durability MonitoringNovel Sensors for Durability Monitoring

Thank youThank youQuestions?Questions?


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k 6 pbasheer

Documents

northern ireland

resultselectrical sensors

structural concrete

fibre optic sensors

structural integritywhat

uknovel sensors

s srinivasan

ukwj mccarter