Table of contents M. McKenzie Guidelines on the selection of innovative techniques for the...

Table of contents

M. McKenzie Guidelines on the selection of innovative techniques for the rehabilitation of concrete highway structures 3A. Žnidarič Optimised assessment of bridges 31E. Denarié Ultra High Performance Fibre Reinforced Concretes (UHPFRC)

for rehabilitation – 1. Motivation and Background 69M. Richardson Guidance on use of surface-applied corrosion inhibitors

Context and Framework of Guidance 97A. Žnidarič Optimised assessment of bridges

Case study 1 - Medno bridge - Soft Load Testing 135A. O’Connor Optimised assessment of bridges

Case study 2 – Danish examples 149JC. Putallaz Ultra High Performance Fibre Reinforced Composites (UHPFRC)

for rehabilitation - 2. Case study – first application 165M. Richardson Guidance on use of surface-applied corrosion inhibitors

Workshop on detailed guidance and Case Studies 197E. Brühwiler Advances in rehabilitation of highway structures Discussion, Summary and Perspectives 233

Guidelines on the selection of innovative techniques for the rehabilitation of concrete highway structuresMalcolm McKenzieTRL Ltd, UK

Development Team

• Richard Woodward, TRL Ltd• Team:

Ales Žnidarič ZAG Mark Richardson UCD Emmanuel Denarié EPFL Tomasz Wierzbicki IBDIM Alan O’Connor TCD Professor Joan Casas UPC Ciaran McNally UCD Malcolm McKenzie TRL Bill McMahon TRL

Overview

• Guidelines and innovation• Deteriorating concrete structures• Selecting the ‘best’ rehabilitation option

for a structure• Special procedures for innovative

techniques• Ranking projects when budgets are

limited

GUIDELINES NOT RULES

Guidelines and innovation

• Innovation is an essential part of engineering development

• Materials and techniques are always being improved

• There are acknowledged problems with existing rehabilitation techniques

• Cautious approach aimed at controlling risks and developing experience

• Yesterday’s innovation is today’s tradition

Concrete bridge deterioration

Some deterioration mechanisms

• Reinforcement corrosion• Alkali silica reaction• Freeze/thaw effects• Sulfate attack• Cracking (settlement, thermal)• Overloading• Impact damage

Identification of problem

• Cause• Extent• Importance

based on

• Inspection• Structural Assessment

MAINTENANCE OPTIONS

• Do nothing• Monitor further deterioration

• Carry out remedial treatment• Carry out strengthening

• Replace element or structure

Procedure

Is option innovative

Identify need

Select & rank rehabilitation option

Control risks

Y

Apply TechniqueN

OptionsAvailable

Innovative techniques: additional risk

Lack of a long established track record

Uncertainties in:• Conditions under which they will be effective• Side effects• Long term durability• Implications for future maintenance• Monitoring effectiveness

Balance conflicting Issues

Technical aspects need to be considered along with other relevant factors to meet the needs of current and future customers.

COST TIME ENVIRONMENT

Wallet

Cost of repairs

Running costsImpact on local

economy

Cost of delays

Affordability

Renewal costs

Watch

Time of works User delays

When Life of repair

World

User delays

Raw materials

Energy usage

Transport of materials

Noise

Pollution

Aesthetics

• Rigorous

• Engineering Judgement

Decision making - WWW

Rigorous approach

• Methodology

Convert everything to financial value

Minimise cost over life of structure

• Problems

Conversion to money

Lack of data

Not practicable

Engineering Judgement

• Advantages

Simple to use

Allows engineer to take all factors into consideration

• Problems

Subjective

Decisions could vary

Structured Engineering Judgement

• Formalise the decision making process• Justification of decisions at each stage

• Best option for a structure• Rank individual projects

• Independent review eg via a Workshop

Decision criteria

• Define objectives of the rehabilitation• Define factors to be considered

• Define decision criteria Basis of comparison eg whole life cost Relative importance of each factor Subjective or numerical approach

Select rehabilitation options

• Identify potential options

• Implications of using an innovative technique

• Assessment of options in relation to decision criteria

taking account of any additional actions resulting from innovative procedure

• Recommend option(s)

Assessing innovative techniques

• Desk study of structure and environmental conditions relevant to technique

• Laboratory testing• Feasibility trials

• Cost/time implications

Select technique - 1

Example: Reinforcement corrosion

• Early Stages• Few visible defects• Low levels of chloride• Half-cell potentials mainly passive• Low corrosion currents

• Preventative maintenance• Slow down chloride ingress eg surface

treatment• Corrosion inhibitors to prevent corrosion?

Select technique - 2

Example Reinforced concrete

• Visible defects• Higher chloride levels• More negative half cell potentials• Higher corrosion currents

• Concrete repairs• Electrochemical techniques• Corrosion inhibitors to reduce corrosion

rates??

Prioritise competing projects

• Risk associated with not carrying out maintenance

• What is the consequence of this occurring? Safety Functionality Sustainability Environment

• What is the likelihood of this occurring?

Prioritisation – Scoring

• This comprises three parts:

• Risks averted• Added value• Timing

All ranked on a numerical basis

Procedure

Is option innovative

Identify need

Select & rank rehabilitation option

Control risks

Y

Apply TechniqueN

OptionsAvailable

InspectionAssessment

Innovativetechniques

Decision

User

Experience

Guidelines and innovation

• It is wise to be cautious in the use of innovative techniques

• It is foolish to be over-cautious

• Engineers need to take controlled risks to grow confidence in new techniques

• Today’s innovation is tomorrow’s tradition

THANK YOU FOR

YOUR ATTENTION

Optimised assessment of bridges

Aleš ŽnidaričSlovenian National Building and Civil Engineering Institute

Contents

• General about bridge assessment• Load testing• Traffic loading

Static Dynamic

• Conclusions

Why optimised assessment?

Design vs. assessment

• new bridges are designed conservatively: uncertainty about

increased loading inexpensive to add

capacity

• assessment should be less conservative: expensive to strengthen/replace or post a bridge capacity and loading can be

measured/monitored

Design vs. Assessment

New bridges: high uncertainties:

• conservative capacity • design loading

schemes• design methods

high safety factors unnecessary:

• costly rehabilitation• load limits

Existing bridges: better defined inputs:

• realistic capacity• realistic loading• assessment methods

lower safety factors savings:

• cheaper rehabilitation• posting of bridges

Why optimised assessment?

• to select optimal rehabilitation measures: do nothing protect repair strengthen replace

Assessment of existing bridges

Important factors : condition, level of

damage structural safety:

• carrying capacity• loading (dead, traffic,

dynamic loading)• reliability of data

serviceability (clearances, traffic, obsoleteness)

service life, importance

1. What is the carrying capacity?• age, condition,

drawings…2. What is the real

behaviour?• influence lines• load distributions

3. What is the real loading?• in a country, type of

road, on specific bridge• dynamic amplification5-level assessment

Condition assessment

• Objectives: Detect possible deterioration processes Indication of the condition of:

• structure • its elements • highway structure stock

Ranking the structures Optimisation of budget allocation


Influencing factors affecting deterioration: Design stage:

• Detailing• Durability• Materials

Construction stage Loadings Maintenance


D19. Report on assessment of structures in selected countries: condition rating:

• Cumulative• Highest value

4 factors:1. Type of damage and its affect

on the safety, serviceability and/or durability2. Maximum intensity3. Influence of the affected structural member on safety,

serviceability and durability of the whole structure or its component

4. Extent and expected propagation


Handbook of damages: http://defects.zag.si/ 10 types of damages descriptions:

• affected bridge component• influencing factor: design,

material, construction, overloading, environment and maintenance

• specific influencing factor• additional data or

explanations• photos

Living application

http://defects.zag.si/



Safety assessment

• to verify that a structure has adequate capacity to safely carry or resist specific loading levels:

R>S

Load testing Live load assessment (static and dynamic)

• How to relate condition and capacity?

R

kSk

RS

Load testing

on bridges that seem to carry out normal traffic satisfactorily, but fail to pass the assessment calculation

the available model of the bridge does not perfectly match with the real bridge itself

to supplement and check the assumptions and simplifications made in the theoretical assessment

To optimise bridge assessment by finding reserves in load carrying capacity

Load testing

benefits: less severe

rehabilitation measures less traffic delays tremendous savings

drawbacks: very costly danger of damaging the

structure

• best candidates: difficult structural modelling lack of documentation

(drawings, calculations,…) when savings are greater than the cost of load test

Load testing

• Types of load test: proof diagnostic soft

Soft load testing - advantages

• the lowest level of load application• uses bridge WIM to provide:

“normal” traffic data information about structural behaviour of the bridge:

• influence lines• statistical load distribution• impact factors from normal traffic.

• “quick&cheap”: no need for pre-weighed vehicles no need to close the traffic

• no risk of overloading and damaging of the structure

BWIM shema

Strain measurementsStrain measurementsStrain measurementsStrain measurements

Axle detectionAxle detectionAxle detectionAxle detection

Soft load testing

• Theoretical vs. measured influence line

Soft load testing – limitations

• not intended to predict the ultimate state behaviour

• validity of bridge assessment is often short-term and depends on the level of safety

• if higher traffic loading is expected, measurements should be extended or replaced by a normal diagnostic load test

• the soft load testing procedure has only been tested and used on bridges shorter than 40 m

• requires an experienced engineer who can realistically evaluate situation

Traffic load modelling

• calibrated notional load models (loading schemes) for: design assessment (rating loading schemes)

• site specific modelling based on traffic data: Monte Carlo simulation simplified models (convolution)

0%

5%

10%

0 10 20 30 40 50 60

GVW (Tonnes)

Fre

qu

en

cy

0%

5%

10%

0 10 20 30 40 50 60

GVW (Tonnes)

Fre

qu

en

cy

0%

5%

10%

0 10 20 30 40 50 60

GVW (Tonnes)F

req

ue

ncy

0%

5%

10%

0 10 20 30 40 50 60

GVW (Tonnes)

Fre

qu

en

cy

Truck histograms from Europe

Truck histograms from Europe

There is an urgent need for effective overload enforcement – better compliance with legal limits will greatly reduce traffic loading on bridges.

Comparison of sites in NL and SI

0,00,10,20,30,40,50,60,70,80,91,0

10 20 30 40

Bridge Length (m)

Ch

ara

cte

risti

c M

om

en

t

NL - Site 1 NL - Site 2NL - Site 3 SI - Site 1SI - Site 2 SI - Site 3

Dynamic Amplification Factor

• problem: combining the extremes of dead load and dynamic effects => very high DAF

• options: codes – conservative modelling – time-consuming and difficult

due to many unknowns measurements – promising, but only

possible since recent development of bridge WIM systems


Case Study Calculating dynamic amplification for 1000-year extreme loading event: Mura River Bridge, Slovenia 2 lanes, opposing directions extensive Monte Carlo static

load simulation – 10 years identified 100 max-per-

month static loading events


Case Study• FE model of

bridge and 5-axle articulated vehicles

• Calibrated by site measurement

• Considered edge beam• Found total effect for each

max-per-month event


Case Study• Max-per-month

Data of static vs. total • Fit to bivariate

extreme value distribution

• Extrapolated the trend to the 1000-year situation

• Dynamics was very small – less than 6%


SAMARIS experiment: 31-m long span to assess influence

of pavement unevenness

to evaluate DAF for 1000’s of vehicles

upgraded SiWIM system


-3,5

-3,0

-2,5

-2,0

-1,5

-1,0

-0,5

0,0

0,5

1,0

0 1 2 3 4 5 6

Str

ain

(V

)

Static

Dynamic

-4,0

-3,5

-3,0

-2,5

-2,0

-1,5

-1,0

-0,5

0,0

0,5

1,0

0 0,5 1 1,5 2 2,5 3

Str

ain

(V

)

Static

Dynamic


-4,0

-3,5

-3,0

-2,5

-2,0

-1,5

-1,0

-0,5

0,0

0,5

1,0

0 0,5 1 1,5 2 2,5 3

Str

ain

(V

)

Static

Dynamic

-4,0

-3,5

-3,0

-2,5

-2,0

-1,5

-1,0

-0,5

0,0

0,5

1,0

0 1 2 3 4 5 6 7 8 9

Str

ain

(V

)

Static

Dynamic


• Before resurfacing

0,91,01,11,21,31,41,51,61,71,81,92,02,1

0 4 8 12 16 20 24 28 32

Strain (V)

DA

F

One vehicle - Lane 2


MP with a light vehicile

MP of heavy vehicles

Slovene Bridge design code

Sem

i-tr

aile

r 40 t

ons


• After resurfacing

0,91,01,11,21,31,41,51,61,71,81,92,02,1

0 4 8 12 16 20 24 28 32

Strain (V)

DA

F



MP with a light vehicile

MP of heavy vehicles

Slovene bridge design code

Sem

i-tra

iler

40 t

ons


Average value Coefficient of variation

100%

102%

104%

106%

108%

110%

112%

0 5 10 15 20 25

Before resurfacing

Af ter resurfacing

0%

2%

4%

6%

8%

10%

12%

0 5 10 15 20 25

Before resurfacing

Af ter resurfacing

Conclusions (1/2)

• Design conservatively, assess optimally• Proper assessment (with monitoring) can:

prove that many existing bridges are safe in their current condition for their current loading: factors from Eurocodes are too high for

assessment of existing bridges• traffic patterns in EU, EEA and CEC are different• carrying capacity is higher than expected

justify optimal rehabilitation measures save a lot of money

Conclusions (2/2)

• soft load testing is proposed as a simpler way of defining real bridge behaviour

• dynamic amplification factors for the extreme load cases are considerably lower than specified in the design codes

• additional topics in the D30: factors required for efficient bridge inspection specifications for diagnostic load test several case studies

Acknowledgment

WP 15 team: ZAG Ljubljana: Igor Lavrič, Jan Kalin UCD Dublin: Prof. Eugene O’Brien, Colin

Caprani, Gavin OConnell, Abraham Getachew

TCD Dublin (now Rambøll): Alan O’Connor UPC Barcelona: Prof. Joan Casas IBDiM Warsaw: Tomasz Wierzbicki

Ultra High Performance Fibre Reinforced Concretes (UHPFRC) for rehabilitation – 1. Motivation and Background

Emmanuel DenariéLaboratory for Maintenance and Safety of Structures Laboratory for Maintenance and Safety of Structures (MCS)(MCS)

OUTLINE

1. Introduction2. UHPFRC materials3. What is proposed?4. Why?5. Validation6. Conclusions7. Acknowledgements

1. Introduction

Road networks = variety of structures, with a variety of sizes, geometries, local conditions, and …common weak zones

Exposures to environmental loads

Most severe = contact with liquid water - XD2, XD3, XA2,3

Reinforced concrete cannot withstand it for a long time !

2. UHPFRC materials

•Ultra compact cementitious matrix•Multilevel fibrous reinforcement•Outstanding mechanical and protective

properties

CEMTECmultiscale® developed by Rossi et al. (2002)

“Selfcompacting” “Ductile as steel”

UHPFRC composition

• Silica fume - SF/C = 0.26 (mass)• Superplasticizer – SP/C = 1 % (mass, dry extract)• Water/Binder = 0.125 to 0.140• Cement: 1051 to 1434 kg/m3

MicrosilicaCement

CEM I 52.5Fine sand

Dmax=0.5 mm

Matrix

UHPFRC composition

• Steel wool + 10 mm/0.2 mm straight fibres • Total dosage 468 - 706 kg/m3 (6 to 9 % Vol.)

Fibrous reinforcement

MicrofibresSteel wool

MacrofibresL=10 mm, D=0.2 mm

CEMTECmultiscale® developed by Rossi et al. (2002)

Fractured surface of UHPFRC with pulled-out steel fibres

10 mm

3. What is proposed ?

Long-lasting, targeted « hardening » of critical zones subjected to severe mechanical and environmental loads

« Apply an everlasting winter coat on bridges »« Apply an everlasting winter coat on bridges »

Concept of application

Cast in place waterproof UHPFRC overlay No thermal treatment, moist curing 8 days

Pavement applied without waterproofing membrane

« An everlasting wintercoat for bridges »« An everlasting wintercoat for bridges »

Concept of application

Combine UHPFRC and rebars to reinforce structures

« An everlasting wintercoat for bridges »« An everlasting wintercoat for bridges »

3. Why ?

• Rehabilitation works are becoming the dominant activity in road construction

Consider impact on a network and society !• Rehabilitations are too often short lived !• Increase load carrying capacity without

increasing deadweight• Limit duration and number of interventions

during service life simplify and shorten !

Combine materials in efficient structures !

4. Validation

• Method of concrete replacementStudy composite UHPFRC-concrete construction

• Consider local conditionsApplication on inclined substrates

• « New material »Test on a wide range of scales of time and

dimensionsProvide guidelines for design and use

• Validate use with existing facilities and tools

Replacement of existing concrete

Successful « Structural rehabilitations » are a major challenge

Major issues:

Processing

Monolithic behaviour

Protective function

Mechanical performance

Durability

Restrained shrinkage

Silfwerbrand (1997)

Stress = stiffness × free strain × degree of restraint

Stiffness: f(Emod, creep/relaxation) material property,Free strain: material property

Degree of restraint: structural property

Typical values: -New layer on bridge deck slab: 0.4 to 0.6

-New layer on stiff beams: 0.6 to 0.8

-New kerb cast on bridge deck: 0.75

-Full restraint: 1.00

Study structural configurations with various degrees of restraint

Summary of R & D worksOngoing studies at MCS-EPFL since 1999.

• Early age and long term behaviour of composite members with UHPFRC

• Composite structural members with UHPFRC, with various geometries: beams, slabs, walls

• Fatigue of composite members with UHPFRC• Tensile behaviour of UHPFRC• Effect of damage on permeability of UHPFRC• Time-dependent behaviour of UHPFRC (creep,

shrinkage)• Combination of UHPFRC with reinforcement bars• Rheological behaviour at fresh state• Numerical modelling and design tools

Range of studies

Creep, shrinkage, permeability

Structural response

Res

ista

nce

Uniaxial tensile response – strain hardening

Modulus of elasticity 30 % higher than normal concretes Tensile strength of matrix 3 to 4 x higher than normal concrete Finely distributed multiple cracking during hardening phase Similarity with yielding of metals (Luders strips)

CEMTECmultiscale®

Mechanical propertiesDenarié et al. (2006)

UHPFRC NC

Compressive strength

[MPa]

160-250 ~ 40

E modulus[GPa]

48-60 ~ 35

Tensile strength

[MPa]

9-20 ~ 3

Strain hardening

[%] 0.05 - 0.2 0

First crack strength

[MPa]

7-16 ~ 3

NC: Normal Concrete

General overview

Structural response

540

150 240 150

f1 f3f2

30

hU

f5f4

30

F F

60 60 60 60120 120

15

ODS U ODS L

3.4

2,5

200

f6 f7UHPFRC

RC

20 20

+

Flexural tests on composite beams with UHPFRC, Habel (2004)

Effect of new UHPFRC layer thickness (hu) Effect of combination of UHPFRC with rebars

Flexural tests on composite beams with UHPFRC, Habel (2004) UHPFRC alone = significant stiffening UHPFRC + rebars = stiffening + increase of load carrying capacity

Structural response

NL: 10 cm

NL: 5 cm

New layer: UHPFRC New layer: UHPFRC + rebars

Analytical modelling

Composite UHPFRC-Concrete structures = multi-layer systems Tensile behaviour of UHPFRC can be taken into consideration Take eigenstresses into consideration for design !

Tensile response of UHPFRC

Habel (2004)

Compression - UHPFRCTension – UHPFRC

UHPFRC

Reinforced

Concrete

Main results of R & D works - 1

• UHPFRC and concrete behave monolithically in composite members, up tp ULS, Habel (2004).

• Interface roughness of 5 mm with wavelength 15 mm is sufficient for monolithic behaviour, Wuest et al. (2005), Herwig et al. (2005)

• UHPFRC exhibit moderate shrinkage (0.6 ‰ after 3 month), and significant viscoelasticity, (creep coeff ~ 0.8) Habel (2004), Kamen et al. (2005), AFGC (2002).


• Under full restraint (worst case), eigenstresses under shrinkage remain moderate (~ 50 % of tensile strength), Kamen et al. (2005)

• Eigenstresses decrease the apparent tensile strength of UHPFRC in composite members, Habel (2004), Clevi (2005), Sadouki et al. (2005) consider for design

• Anisotropic orientation of fibres, function of application consider impact on properties


• Very low transport properties for liquids (sorptivity) and gases, Charron et al. (2004).

• Up to equivalent crack openings of 0.1 mm (strain of 0.1 %) permeability remains very low, Charron et al. (2004), and behaviour under fatigue loading is controlled, Herwig (2005).

• Self-healing capacity for microcracks• Promissing combination of UHPFRC with rebars,

for reinforcement of structures, with no increase of dead weight, Brühwiler et al. (2005), Habel (2004), Wuest et al. (2005).

Geometries of application

P: UHPFRC hu= 15 to 30 mm = Protection

PR: UHPFRC + replacement of corroded rebars (hu~ 50 mm) = Reinforcement

R: UHPFRC + additional rebars (hu>=50 mm) = Reinforcement

Habel et al. (2004)

Recommandation: UHPFRC

Apply UHPFRC where it is worth it! For zones of severe exposure classes (XD2,3, evt. XA2,3)! To improve existing or new structures!

7. Conclusions

«Targeted local hardening» of highway structures, in most critical zones, by using UHPFRC.

Simplification of the construction process. Reduction of the dead loads

(superstructure and pavement). Increase of the performance of existing and

new structures (protection and reinforcement).

Dramatic decrease of the number and severity of interventions during service life.

Concept has been technically validated on a wide range of scales and duration

Acknowledgements

• UHPFRC team of MCS-EPFL: Prof. Eugen Brühwiler, John Wuest, Aicha Kamen, Andrin Herwig, Dr. Katrin Habel*, Prof. J.P. Charron*, Roland Gysler, Sylvain Demierre,

* Former collaborators of MCS-EPFL

• Partners in Project SAMARIS

Dr. P. Rossi Dr. R. Woodward

Guidance on use of surface-applied corrosion inhibitorsContext and Framework of GuidanceMark RichardsonUniversity College Dublin

Work Package Team

UCD M. Richardson (Team Leader),C. McNally, T. A. Soylev.E. Grimes

ZAG A. Legat

TRL M. McKenzie

Sika P. Mulligan, B. Marazzani, M. Donadio

Cardiff University B. Lark

C-Probe Systems Limited /Structural Healthcare Associates G. Jones

Outline

Background– Methodology, Concept, Motivation

Objectives of SACI in a Maintenance Strategy– Reactive and Proactive Context

Primary Factors Influencing Effectiveness

Framework of Guidance for Specifiers of SACI

Background to SACI

• Methodology

• Concept

• Motivation

Methodology

SACI are applied to mature concrete surfaces where they are absorbed.

Penetrate through the cover concrete by capillary action and diffusion.

Form a protective layer on the reinforcement.

Concept

Before: uncontrolled corrosion activity (existing or future)

After: delay in onset and/or control of corrosion rate

Evans DiagramEvans Diagram

Potential (E)Potential (E)

anodic reactionanodic reaction

cathodic reactioncathodic reaction

Current (I)Current (I)


E E corrcorr

I I corrcorr


After inhibitor applicationAfter inhibitor application



After inhibitor applicationAfter inhibitor application


E E corrcorr

I I corrcorr


Motivation

Benefit of SACI compared to ‘traditional’ repair optionReduce disruption to road users during rehabilitation of structure by time and access efficiency

Sustainability aspect in preventative maintenanceArrest deterioration before it becomes significant and costly to repair

Objectives of SACI in Maintenance Strategy

• Objectives related to overall maintenance strategy

• Specifically consider objectives in ‘Reactive’ and ‘Proactive’ strategies

Reactive Maintenance Strategy

• Inhibitor may be used to reduce (or at least prevent an increase) in the rate of corrosion, thus extending residual service life, unless extent of corrosion is too advanced.

Time

Service life extension

With inhibitor

Without inhibitor

Limit

Deterioration Level

• However in a more general context note that:

Repair occurs when deterioration is apparent and possibly significant

Residual capacity of existing structure may be significantly diminished at time of intervention

Proactive Maintenance Strategy

• Inhibitor may be used to delay the onset of depassivation and thereafter positively influence the rate of corrosion, thus extending residual service life.

Time

Service life extension

With inhibitor

Without inhibitor

Limit

Deterioration Level

• Also in a more general context note that: Measures for performance monitoring of the

structure could be included at time of repair.

Inhibitor may be subsequently reapplied (e.g. a decade later) if performance monitoring indicates it is warranted, before deterioration becomes significant.

Parameter

Time

Resistance Rp,

Corrosion rate, µm/yr

Inhibitor applied

Inhibitor re-applied

Primary Factors Influencing Effectiveness

Effectiveness is influenced by:

Ability of surface to ‘take up’ the inhibitor Ability of inhibitor to penetrate the cover

concrete Ability of inhibitor to form a layer on the

reinforcement Ability of inhibitor to sustain the protective

layer

Appropriateness of SACI

Appropriateness of SACI therefore depends on the following primary factors: Degree of saturation of concrete Permeability characteristics of concrete Corroded state of reinforcement at time of

repair Chloride levels

Degree of saturation of concrete

• State of surface at time of application (initial take-up)

• Surface condition immediately after application (wash out)

• Influence on permeability

Permeability characteristics of concrete

• Ease with which inhibitor may penetrate depends on intrinsic permeability characteristics and degree of saturation

• Permeability also influences ease which other contaminants may enter post-repair (additional protection from suitable coating may be required)

Corroded state of reinforcement

• Inhibitor must form mono-molecular layer on reinforcement

• Ease of formation depends on surface state at time of repair

• Clean or lightly corroded – optimal state

• Heavily corroded – outside inhibitor’s effectiveness window

Chloride levels

• Critical consideration is the relative inhibitor to chloride concentration

• Inhibitor must form a mono-molecular protective layer and displace chloride ions from the reinforcement

• Competitive surface adsorption reaction between inhibitors and chloride ions

• Inhibitors most effective if applied before significant build up of chloride concentration

Framework of Guidance for Specifiers

• Specifiers evaluating or developing a repair strategy based on surface applied corrosion inhibitors are encouraged to view it in the context of a structured approach to deciding on an optimum repair strategy.

• Such a structured approach is presented in SAMARIS Report D31.

Context for Guidance: SAMARIS D31

Determine condition

Rank maintenance option

(Value Management)

Control risks

Apply technique

Select maintenance option

(Value Engineering)Options available

No

Yes

Innovative?

Objectives of maintenance

Identify need

Determine

Rank option

Control risks

Apply technique

Select optionOptions

N

Y

Innov?

Objectives

IdentifySAM

ARIS D

31 G

uida

nce

SAMARIS

D25

a G

uida

nce

Framework of Guidance: D25a

Reference: SAMARIS Report D25a

Summary Flowchart

Yes

Apply technique

No

Initial desk study assessment

Inhibitor potentially

appropriate?

Control of risk to specifier’s

satisfaction?

Re-examine alternative ranked

options

No

Yes

• Overview of guidance flowchart


Conduct preview and analyse results

No

YesControl of risk to

specifier’s satisfaction?

Define performance criteria for preview

Finalise proposed rehabilitation strategy


If resources permit conduct post repair monitoring as part of a proactive maintenance strategy and reapply technique if required during residual service life

Control of risk to specifier’s

satisfaction?

Apply technique


Re-examine alternative

ranked options

Yes

No

Summary

• Initial Assessment:

• Consider findings, • Balance constraints (funding, time,

urgency, traffic disruption etc.) against control of risk to specifier’s satisfaction,

• Decide: • Go? No go? Go to preview study?

Summary

• Preview Study Assessment (if used): • Consider findings, • Modify proposed strategy if necessary (e.g.

inhibitor + coating rather than inhibitor only),

• Balance constraints (funding, time, urgency, traffic disruption etc.) against control of risk to specifier’s satisfaction,

• Decide: Go? No go?

• Post-repair monitoring• If ‘Go’ consider also follow up monitoring

as part of a proactive maintenance strategy

Further Information

• Follow up presentation • (Guidance on use of surface-applied

corrosion inhibitors: Detailed Guidance and Case Studies)

• SAMARIS Report D25a

Optimised assessment of bridges Case study 1 - Medno bridgeSoft Load TestingAleš ŽnidaričSlovenian National Building and Civil Engineering Institute

Assessment of existing bridges

Important factors: condition, level of

damage structural safety:

• carrying capacity• loading (dead, traffic,

dynamic loading)• reliability of data

serviceability (clearances, traffic, obsoleteness)

service life, importance

1. What is the carrying capacity?• age, condition,

drawings…2. What is the real

behaviour?• influence lines• load distributions

3. What is the real loading?• in a country, type of

road, on specific bridge• dynamic amplification5-level (step-by-step) assessment

Safety assessment

• to verify that a structure has adequate capacity to safely carry or resist specific loading levels:

R>S

Rating factor:

R

kSk

RS

QQ

nGd

GGR

RF

Case study – Medno bridge

Structure from 1937: no drawings refurbished in 1997 in very good condition 11.95 m long span total width 8.5 m 5 RC beams 1.35 m apart cross beams above

abutments, at ¼, ½ and ¾ of the span

unknown fixity of supports located on a road with 1150

heavy vehicles ADT posted to 30 tonnes GVW

Carrying capacity

• Assumed characteristics of concrete:

fc = 20 MPa

no information about steel reinforcement: 8 bars from profometer test likely 25 or 28 mm,

assumed 822 mm bars of 240/360 MPa steel

RM = 867.4 kNm

Soft load testing

• to check the assumptions made in the model• bridge WIM used to provide:

normal traffic data (not in this case) information about structural behaviour:

• influence lines• statistical load distribution• impact factors from normal traffic (not in this

case) only 1 pre-weighed vehicle for BWIM

calibration the bridge need not be closed to traffic

BWIM shema

Strain measurementsStrain measurementsStrain measurementsStrain measurements

Axle detectionAxle detectionAxle detectionAxle detection

Soft Load Testing

Soft load testingSimply supportedSimply supportedRF RF << 1.0<< 1.0

Soft Load Testing

Soft load testingSimply supportedSimply supportedRF RF << << 1.01.0

MeasuredMeasuredRF RF >>>> 1 1.0.0

Message:Message:Check, how Check, how bridges really bridges really behave.behave.

Soft Load Testing

Load distribution: normally guestimation bridge WIM evaluates it statistically

± 0

Regular inspection

R factor

Service life

Resistance

Normal Limited

Design

Testing Estimate

= 0.85

Severe

Minor

Bad Good

Redundancy No

Detailed inspection

Yes

No

c = 3.5

c = 2.5

VR = 10% VR = 15% VR = 20% - 0.1

+ 0.1

> 0.95

+ 0.05

0.95

- 0.15

+ 0

- 0.2

No

Average

Yes

No

No Yes

BR×e

R×C×VR

Maintenance

Yes

START

Deterioration

Selection of capacity reduction factor

Capacity reduction factor:

Φ = BR × e -.βc.V

SI procedure accounts for: condition of the structure reliability of data redundancy of structure method of calculation

Medno bridge:Φ = 0.86

Selection of safety factors

Dimensions taken on site:

Safety factor for traffic loading:

WIMEstimated

Estimated

Traffic loading

Rating loading schemes

Lateral loaddistribution

Measured

Q 1.4

Q 1.6

Q Q + 0.2

Q Q - 0.2

Q Q + 0.1

Q Q + 0.1

Estimated

Impact factor

Measured

Service life Limited

Q Q - 0.2

Normal

Yes

Q Q + 0.2

>1000 trucks/day

No

Q = 1.6

G = 1.2

Q = 1.7Q = 1.9

Structural safety of Medno bridge

Calibrated structural model:1. Loading scheme with 2 4-axle rigid 38-ton

trucks, one in each lane:

1.03

28.16.2349.1

7.2352.14.86786.0

QQ

nGd

GGR

RF

2. Loading scheme with 81-ton 8-axle vehicle in one lane and rigid 38-ton truck in the other:

1.08

00.15.2469.1

7.2352.14.86786.0

QQ

nGd

GGR

RF

Room for further optimisation of analysis

Conclusions

• on Medno bridge soft load testing proved beneficial

• 2004 assessments for special transports for the Slovene Road Administration: 13 posted bridges assessed 11 proved safe even for a

165-tonnes special vehicle with 12 axles

for the rest missing data on carrying capacity

on shorter bridges normal traffic worse than special transports

Optimised assessment of bridges Case study 2 – Danish examplesAlan O’ConnorRambøll

Problem:

1) Lack of load carrying capacity or exceedance of structural/performance limit state due to

– weak bridges– deteriorated/(ing) bridges– Increasing loads

2) Low budgets for strengthening

and/or rehabilitation where required

Idea: 1) Demonstration of higher capacity through Probabilistic safety assessments incorporating better calculation/response models

Principal Motivation:

Cost saving through Budget Optimisation

Problem, idea and motivation

The general approach:

Assessments based upon deterministic

codes for both (a) New bridges and (b) Existing bridges

Generalisation

• Partial safety factor format

• Deterministic Load specification

• Many types of bridges

BenefitEfficient and easy to use

DrawbackCostly in case of lack of capacity may result in unnecessary repair/rehabilitation

Safety approaches for assessment of existing bridges

Concept:

• Not necessarily have to fulfill the requirements of a general code rather the Overall requirement for the safety level must be satisfied on a individual basis

Purpose:

• Cut strengthening or rehabilitation costs without compromising safety level

Method: Probabilistic-based assessment

Site specific modelling of specific conditions/structure:

• Traffic load

• Capacities

• Response Models

Bridge specific “code” is obtained

The individual approach

Decision Process

Yes

Yes

No

No

No

Yes

Assessment from traditional evaluation OK ?

Implement traditional strengthening project

Yes

Assessment from traditional evaluation OK ?

Implement traditional strengthening project

Refinedassessment beneficial?

No

Refined strengthening project

Traditional decision process

New decision process considering refined assessment

Refinedassessment OK ?

Case Studies

Practical experience: The Danish Road Directorate has saved more than $50 million USD Bridge Deterministic Analysis Probability-based as-

sessment Cost Saving

Mio. $US Vilsund Max W = 40 t Max W = 100 t 4 Skovdiget Lifetime ~ 0 years Lifetime > 15 years 15.0 Storstroem Lifetime ~ 0 years Lifetime > 10 years 20.0 Klovtofte Max W = 50 t Max W = 100 t 2 407-0028 Max W = 60 t Max W = 150 t 1.5 30-0124 Max W = 45 t Max W = 100 t 0.5 Nørresø Max W = 50 t Max W = 100 t 0.3 Rødbyhavn Max W = 70 t Max W = 100 t 0.5 Åkalve Bro Max W = 80 t Max W = 100 t 1.0 Nystedvej Bro Max W = 80 t Max W = 100 t 2.0 Avdebo Bro Max W = 80 t Max W = 100 t 2.0

Case Studies - Savings

Savings > $ 4 mio.Savings > $ 4 mio.

Savings > $ 15 ml.Savings > $ 15 ml.


Savings > $ 0.5 ml.Savings > $ 0.5 ml.


Case Studies - Savings

Savings > $ 0.Savings > $ 0.33 ml. ml.

Savings > $ 0.5 ml.Savings > $ 0.5 ml.

Savings > $ 1.Savings > $ 1.00 ml. ml. Savings > $ 2.0 ml.Savings > $ 2.0 ml. Savings > $ Savings > $ 22.0 ml..0 ml.

Probability based Maintenance Management

0. Fact-finding 1. Formulation of problem 2. Safety requirements 3. Deterministic models for failure 4. Probability-based safety-model for critical failure modes. 5. Stochastic variables 6. Safety of the non-deteriorated bridge 7. Safety of deteriorated bridge 8. Analysis of repair and rehabilitation options 9. Requirements for the visual appearance of the bridge 10. Cost-optimal management plan using decision analysis to determine optimal rehabilitation options

SAFETY

MANAGEMENT

Practical 10-phase procedure

WestBridge

EastBridge

Post tensioned concrete box-girder bridges12 spans, 220 m longCarries a 4-lane highway

Skovdiget Bridges: Location / OverviewSAVING €20ml.

History

West Bridge East bridge

1965-1967 Construction Construction

1978 Majorrehabilitation

1978-1999 Inspection 4 times Principal Inspectiona year. Load testing every 5 years.every 5 years. Normal M & R

procedure.

Bridge in bad Bridge in good condition. condition.

1998-2000 Implementation ofprobabilistic-based management plan.

Design, Deterioration & Assessment

Poor workmanship during construction: un-injected or poorly injected post-

tensioned cable ducts insufficient and poor drainage area around gulley poorly made

bad waterproofing

Fast Slow Service Emergency Bicycle lane &

lane lane lane lane footway

Gulley

Main girder 3

Main girder 4

Deterministic analysis of bridge & failure modes Main girders, moment and shear failure Shear failure of transverse girders (above

columns) Transverse ribs between main girders 3 and 4 East and west cantilever wing

Identifying areas with most severe deteriorationIdentifying critical combinations

Modelling of stochastic variablesModelling of strengths

concrete, reinforcement steel, cables

Modelling of loads total traffic load dynamic amplification factors transverse distribution of vehicles

Model uncertaintiesPrediction of the deterioration

Calculation of safety allowing for deterioration

Development of the safety index

Maintenance Management OptionsTraffic, repair and information options:Traffic options - Weight restrictions Repair/strengthening - or replacement - options - Minor / major repair - or - strengthening - Preventive actions - ReplacementImprovement of Information level- Inspections to update estimate of current

deterioration - Test loading- Determine actual weight the bridge- Monitoring system- More advanced analysis and response models- Extended routine and special inspections

A Safety-based management plan is established and implemented for Skovdiget WestExtended lifetime > 15 years & Cost savings > €20 millionThe Danish Road Directorate is now using the methodology for other bridgesThe safety level is not compromised

A rational methodology is implemented for practical application

Probabilistic-based assessment of bridges cuts strengthening or rehabilitation costs. The cost savings can be significant

www.vd.dk

Conclusions

• Reliability based assessment of bridges and Probability Based Maintenance Management cuts strengthening or rehabilitation costs

• The safety level is not compromised• A well established

methodology is implemented for practical application

• The cost saving can be millions of € per year

Ultra High Performance Fibre Reinforced Composites (UHPFRC) for rehabilitation - 2. Case study – first applicationJean-Christophe Putallaz SRCE/VSEmmanuel Denarié – MCS/EPFLMCS/EPFL

OUTLINE

1. Rehabilitation strategy2. First application3. Conclusions4. Acknowledgements

Rehabilitation strategy

• Limit costs (construction and life-cycle)• Decrease number and duration of interventions• Provide sufficient durability …… Promote STRATEGY APromote STRATEGY A

2. First application


Site application 1 - 2004Structural response

Res

ista

nce

First application

Rehabilitation and widening of the Bridge over river La Morge - Switzerland

Execution: October – November 2004

GEOGRAPHICAL LOCATION

Swiss alps, Valley nearby Sion, 480 m above s.l Secondary road with sustained traffic Heavy salt spraying in winter

Prior to rehabilitation

Downstream kerb Upstream kerb

No waterproofing membrane,Kerbs severely damaged by chloride induced corrosion

Concept of the intervention

Span 10 m No waterproofing membrane

Protective function provided by UHPFRC

Widening of the bridge

Prefabricated UHPFRC kerb downstream

Thin UHPFRC overlay (3 cm) applied on deck

UHPFRC rehab. kerb usptream

Span 10 m

Construction joint for UHPFRC

Prefabricated downstream kerb

Prefabricated kerb in UHPFRC - joint

UHPFRC materials

• Cement CEM I 52.5 (low C3A)• Fine quarz sand (Dmax < 0.5 mm)• Silica fume - SF/C = 0.26• Superplasticizer = 1 % dry extract • Steel wool + 10/0.2 mm steel fibres• Total fibres = 9 % Vol. or 706 kg/m3)

Basis: CEMTECmultiscale® - Rossi et al. (2002)

No thermal curing Protection with plastic sheet + 8 days moist curing

UHPFRC materials

Recipe

Cement[kg/m3]

W/B[--]

W/C[--]

Application

CM22 1410 0.131

0.165

RehabilitationUpstream kerb

CM23 1434 0.125

0.155

Downstream kerb + overlays CM 23: tolerates slope up to 2.5 %

Both recipes are selfcompacting Slump flow ~ 400 mm

Preparation of the UHPFRC

• Concrete plant mixer with 500 to 750 litres capacity • 300 litres UHPFRC pro batch• 3 batches = 900 litres in 45 minutes• 900 litres pro truck - 635 kg steel fibres per truck !

Application on ½ road downstream – october 22, 2004

On the site

Processing of the UHPFRC

The thixotropic, selfcompacting UHPFRC, is handled using simple tools (Photo A. Herzog)

In-situ air permeability testing

Air permeability tests after Torrent et al. (1995)

Extremely low kT values measured on bridge

Comparative uniaxial tensile behaviour

Denarié et al. (2006)

Uniaxial tensile tests on UHPFRC

Test results on 5 specimens, at 28 days

fct = 13.5 MPa (mean)

hardening = 1.5 ‰ (mean)

Denarié et al. (2006)

Cost analysisComparison of three alternatives

A. Executed project with UHPFRC and no waterproofing membrane

B. Similar case with rehabilitation mortar and waterproofing membrane

C. Similar case with cheaper (- 30 %) UHPFRC and no waterproofing membrane

Case Relative construction costs

A 112 %

B 100 %

C 107 %

Realized

The bridge, after first winter

Detail of UHPFRC, after first winter

View of the surface of the prefabricated kerb with UHPFRC, with superficial corrosion of steel fibres tips near to the surface.

UHPFRC cast on site

Prefabricated

Conclusions of first application

UHPFRC CEMTECmultiscale® was easy to produce and cast on site with standard equipments.

Quality of the UHPFRC was verified in-situ and in the laboratory. Excellent properties were achieved.

Waterproofing membrane not necessary with UHPFRC.

Bituminous layer can be applied after 8 days on UHPFRC, instead of several weeks for normal concrete.

Superficial corrosion of steel fibres on UHPFRC skin, is linked to processing.

Although a purely superficial concern, has to be mitigated by adapted processing techniques.

Owner’s point of view

« The main advantages of this technique are:

Shortening of duration of works, quicker reopening of traffic lanes, and longer durability.

Significant savings in terms of reduced traffic disturbances and associated indirect costs.

Reduction of rehabilitation layer thickness and capacity to reinforce without increasing deadweight.

Prevent costly reinforcement of main parts of the structure.

Application by local contractors, with standard equipments. »SRCE - DTEE CANTON DU VALAIS

7. Conclusions

«Targeted local hardening» of highway structures, in most critical zones, by using UHPFRC.

Simplification of the construction process. Reduction of the dead loads (superstructure and

pavement). Increase of the performance of existing and new

structures (protection and reinforcement). Dramatic decrease of the number and severity

of interventions during service life. Concept has successfully demonstrated its

technical maturity and economical feasibility in a first full scale application.

What is the future ?


Site application 2 - 2007

Site application 1 - 2004Structural response

Res

ista

nce

Why not you ?

Partners of the project

Owner:Owner: Département des Travaux Publics du canton du Valais, Sion, Suisse, Département des Travaux Publics du canton du Valais, Sion, Suisse, Service des routes et Cours d'eau, Section du Valais central/Sion, Switzerland.Service des routes et Cours d'eau, Section du Valais central/Sion, Switzerland.

Concept and supervision:Concept and supervision: Laboratory for Maintenance and Safety of Structures, Laboratory for Maintenance and Safety of Structures, Ecole Polytechnique Fédérale de Lausanne (EPFL), SwitzerlandEcole Polytechnique Fédérale de Lausanne (EPFL), Switzerland

Advice for the UHPFRC recipes and processing:Advice for the UHPFRC recipes and processing: Dr. P. Rossi, Laboratoire Dr. P. Rossi, Laboratoire Central des Ponts et Chaussées (LCPC), Paris, France.Central des Ponts et Chaussées (LCPC), Paris, France.

Execution plans and local direction of works:Execution plans and local direction of works: PRA ingénieurs conseil SA, rue PRA ingénieurs conseil SA, rue de la Majorie 9, CH-1950 Sion, Switzerland, de la Majorie 9, CH-1950 Sion, Switzerland,

Production of UHPFRC, realisation of prefabricated UHPFRC kerb and Production of UHPFRC, realisation of prefabricated UHPFRC kerb and reinforced concrete beam:reinforced concrete beam: Proz Frères SA, matériaux de construction, CH-1908 Proz Frères SA, matériaux de construction, CH-1908 Riddes, Switzerland, Riddes, Switzerland,

Contractor:Contractor: Evéquoz SA, rue des Peupliers 16, CH-1964 Conthey, Switzerland, Evéquoz SA, rue des Peupliers 16, CH-1964 Conthey, Switzerland,

Acknowledgements

UHPFRC team of MCS-EPFL: Prof. Eugen Brühwiler, John Wuest, Aicha Kamen, Andrin Herwig, Dr. Katrin Habel*, Prof. J.P. Charron*, Roland Gysler, Sylvain Demierre, *Former collaborators of MCS-EPFL

Partners in Project SAMARIS

Dr. P. Rossi Dr. R. Woodward

Service des Routes et Cours d’Eau – DTEE SRCE – Canton du Valais

Guidance on use of surface-applied corrosion inhibitorsWorkshop on detailed guidance andCase StudiesM. RichardsonUCD

Outline

• Initial Assessment

• Preview Study option

• Post-repair Monitoring option

• Case Study: Assessment and Monitoring – Kingsway Bridge

• Case Study: Post-repair monitoring – Fleet Flood Span Bridge

Initial Assessment

Yes

Apply technique

No

Initial desk study assessment

Inhibitor potentially appropriate

?

Control of risk to specifier’s satisfaction?


ranked options

No

Yes

Summary of Guidance - 1

Issues in Initial Assessment

• Extremes of in-service environmental conditions

• Degree of saturation of concrete• Chloride levels• Permeability and carbonation• Corroded state of reinforcement at

time of repair• Ecological constraints

Issues in Initial Assessment

• Extremes of in-service environmental conditions

• Degree of saturation of concrete• Chloride levels• Permeability characteristics of concrete• Corroded state of reinforcement at

time of repair• Ecological constraints

Extremes of environmental conditions

Environment

IndicativeTemperature

Potential Consequence

Sustained lowtemperatures

≤ -5oC Alteration in the physical nature of the inhibitor, with implications for its mobility in concrete.Temperature limit of –5°C is only applicable for the storage condition.Application to be carried out above +5°C.

Frequent hightemperatures

≥ 40oC Potential loss of volatile material to the atmosphere.Coating the concrete surface may be an option to reduce evaporation loss.

Degree of saturation of concrete

Moisture State

Indicative Example

Possible Consequence

Permanentlysaturated

Elements ofhighwaystructures predominantly below the waterlevel of a lake

Inhibitor take up by absorption would be low.Subsequent penetration would not be assisted by capillary action.

Note: corrosion would be low in these areas if oxygen access is equally restricted.

Frequent and regular wettingcycles

Elements ofcoastal highwaystructures withinthe tidal zone

Potential washout of inhibitor immediately after application.Inadequate concentration at the reinforcement.

Chloride levels

Chloride State

Indicative Free Chloride Ion at

Level at Reinforcement


Low ≤ 0.5 % Chloride ion

by mass of cement

Corrosion inhibitor potentially viable as a preventive maintenance strategy before any significant active corrosion takes place.

Moderate

≤ 1 % Chloride ion

by mass of cement

Corrosion inhibitor may be effective if a satisfactory inhibitor to chloride ion concentration ratio is achieved – much depends on existing degree of corrosion.Protective measures to prevent further chloride build up are recommended in chloride-rich environments.

continued …

Chloride levelscontinued …

Chloride State

Indicative Free Chloride Ion at

Level at Reinforcement


High 1 – 2 % Chloride ion by mass of cement

Corrosion inhibitor dosage level may have to be increased beyond typical manufacturer’s recommendation and additional protective measures required.May take the technique beyond its recommended effectiveness window, introducing higher risk.

Very high

> 2 % Chloride ion by mass of

cement

Corrosion inhibitor unlikely to be a successful component of the repair strategy.

Permeability and carbonation

Carbonation

State

ConcretePermeability


Cover fullycarbonated

Moderate Inhibitor potentially effective.

High Inhibitor potentially effective initially but reservoir may not be retained in concrete reducing effectiveness over time.May need additional measures such as a suitable coating.

Corroded state of reinforcement

continued …

Existing Corrosion Rate

Indicative Corrosion Rate

over a sustained

period


Low to Moderate

< 0.5 µA/cm2

< 5 μm/year

Best scenario possible with inhibitor used as part of a proactive preventive maintenance strategy.

Moderate to High

0.5 – 1.0 μA/cm2

5 - 10 μm/year

State of reinforcement is potentially suitable for consideration of corrosion inhibitor treatment.

Corroded state of reinforcementcontinued …

Existing Corrosion Rate

Indicative Corrosion Rate

over a sustained

period


High 1.0 - 10 μA/cm2

10 - 100 μm/year

State of reinforcement will depend on corrosion rate lies - effectiveness of the inhibitor correspondingly influenced.Higher risk at higher corrosion rate.Corrosion monitoring recommended in case of higher corrosion rates.

Very High > 10 μA/cm2

> 100 μm/year

Reinforcement may be heavily corroded - corrosion inhibitor is unlikely to be a successful component of the repair strategy.

Ecological constraints

Local environmental or health and safety constraints?

Example: work near drinking water supply source

Preview Study option

Conduct preview and analyse results

No

YesControl of risk to

specifier’s satisfaction?

Define performance criteria for preview



Preview Study – Indicative Criteria

Objective Indicative Performance Criteria

Defer the initial time to depassivation

< 5 μm/year loss of steel (or < 0.5 µA/cm2)

Reduce the rate of corrosion

65% reduction from pre-treated levels over a defined time period or ……………

< 5 μm/year loss of steel (or < 0.5 µA/cm2)

Retard incipient action (ring anode)

No increase in loss of steel prefer …………Decrease to < 5 μm/year loss of steel (or < 0.5 µA/cm2)

Post-repair monitoring option



Apply technique



ranked options

Yes

No


Case Study of assessment and monitoring

Kingsway Bridge

Case Study 1

Kingsway Bridge, Warrington, U.K.

Acknowledgement: Warrington Borough Council

• Reinforced concrete• multi-span arch, • 1932

• Main spans, 2 x 26.21m• Reinforced concrete arches• Thickness: 450mm (arch)

1300mm (springings), • Sagging and hogging

bending moments• Drainage route along top

curved surface of arch• Subject to chloride run-off

Environmental conditions Not significant

Degree of saturation Not significant

Chloride levels Typically 0.3% Max. 0.6 –

1.2%

Carbonation 2mm

State of reinforcement Light surface rust

Some pitting

Ecological constraints Over water

Findings from Initial Assessment

• Threat from chloride-induced corrosion.• Chloride-entrained rain and deicing salts

passing through deck and accumulating at crown of arch and later behind springings.

• Surface applied corrosion inhibitors identified as a candidate strategy for rehabilitation.

• Agreement from Warrington Borough Council to allow further investigation including a form of ‘preview’ study of corrosion inhibitors within SAMARIS

• Areas selected:Crown of ArchUnder Arch

• Corrosion inhibitor applied after base measurements

• Monitoring locations established

Corrosion Rates: Crown Arch

0

5

10

15

20

25

30

35

40

6/24

/04

11/3

/04

1/23

/05

2/6/

05

2/20

/05

3/6/

05

3/20

/05

4/3/

05

5/8/

05

5/22

/05

6/5/

05

6/19

/05

9/11

/05

9/25

/05

10/9

/05

10/2

3/05

11/6

/05

11/2

0/05

12/4

/05

12/1

8/05

1/1/

06

C1RC2RC3RC4R

Test Date

Co

rro

sio

n R

ate

(u

m/y

r)

Corrosion Rate Values

C3R Control

C1R Waterproofing

C4R Inhibitor only

C2R Inhibitor plus

waterproofing

Corrrosion Rates: Under Arch

0

4

8

12

16

20

24

6/24

/04

11/3

/04

1/23

/05

2/6/

05

2/20

/05

3/6/

05

3/20

/05

4/3/

05

5/8/

05

5/22

/05

6/5/

05

6/19

/05

9/11

/05

9/25

/05

10/9

/05

10/2

3/05

11/6

/05

11/2

0/05

12/4

/05

12/1

8/05

1/1/

06

F1RF2RF3RF4RF5RF6RX1RX2RX3R

Test Date

Co

rro

sio

n R

ate

(u

m/y

r)Corrosion Rate Values

Case Study: Post-repair monitoring – Fleet Flood Span Bridge

Case Study 2

Concrete repair and corrosion inhibitor treatment to trestles and abutments.

Monitored previously from 2000 to 2002, reactivated 2005.

Fleet Flood Span Bridge

Trestle 1

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

2/14

/00

3/10

/00

3/14

/00

3/16

/00

7/5/

00

11/1

6/00

2/13

/01

4/24

/01

5/21

/02

11/1

6/05

Test Date

Co

rro

sio

n R

ate

(u

m/y

r)


0

4

8

12

16

20

24

28

2/14

/00

3/10

/00

3/14

/00

3/16

/00

7/5/

00

11/1

6/00

2/13

/01

4/24

/01

5/21

/02

11/1

6/05

Test Date

Co

rro

sio

n R

ate

(u

m/y

r)


0

1

2

3

4

5

6

2/14

/00

3/10

/00

3/14

/00

3/16

/00

7/5/

00

11/1

6/00

2/13

/01

4/24

/01

5/21

/02

11/1

6/05

Test Date

Co

rro

sio

n R

ate

(u

m/y

r)


0

2

4

6

8

10

12

14

16

18

2/14

/00

3/10

/00

3/14

/00

3/16

/00

7/5/

00

11/1

6/00

2/13

/01

4/24

/01

5/21

/02

11/1

6/05

Test Date

Co

rro

sio

n R

ate

(u

m/y

r)


Trestle 2

0

0.5

1

1.5

2

2.5

3

3.5

4

2/14

/00

3/10

/00

3/14

/00

3/16

/00

7/5/

00

11/1

6/00

2/13

/01

4/24

/01

5/21

/02

11/1

6/05

Test Date

Co

rro

sio

n R

ate

(u

m/y

r)


0

0.4

0.8

1.2

1.6

2

2.4

2.8

3.2

3.6

2/14

/00

3/10

/00

3/14

/00

3/16

/00

7/5/

00

11/1

6/00

2/13

/01

4/24

/01

5/21

/02

11/1

6/05

Test Date

Co

rro

sio

n R

ate

(u

m/y

r)


0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

2/14

/00

3/10

/00

3/14

/00

3/16

/00

7/5/

00

11/1

6/00

2/13

/01

4/24

/01

5/21

/02

11/1

6/05

Test Date

Co

rro

sio

n R

ate

(u

m/y

r)


0

0.4

0.8

1.2

1.6

2

2.4

2.8

3.2

3.6

2/14

/00

3/10

/00

3/14

/00

3/16

/00

7/5/

00

11/1

6/00

2/13

/01

4/24

/01

5/21

/02

11/1

6/05

Test Date

Co

rro

sio

n R

ate

(u

m/y

r)


North Abutment

1

2

3

4

5

6

7

8

9

10

2/14

/00

3/10

/00

3/14

/00

3/16

/00

7/5/

00

11/1

6/00

2/13

/01

4/24

/01

5/21

/02

11/1

6/05

Test Date

Co

rro

sio

n R

ate

(u

m/y

r)


0

5

10

15

20

25

30

35

40

2/14

/00

3/10

/00

3/14

/00

3/16

/00

7/5/

00

11/1

6/00

2/13

/01

4/24

/01

5/21

/02

11/1

6/05

Test Date

Co

rro

sio

n R

ate

(um

/yr)


0

10

20

30

40

50

60

2/14

/00

3/10

/00

3/14

/00

3/16

/00

7/5/

00

11/1

6/00

2/13

/01

4/24

/01

5/21

/02

11/1

6/05

Test Date

Co

rro

sio

n R

ate

(u

m/y

r)


South Abutment

0

1

2

3

4

5

6

7

8

2/14

/00

3/10

/00

3/14

/00

3/16

/00

7/5/

00

11/1

6/00

2/13

/01

4/24

/01

5/21

/02

11/1

6/05

Test Date

Co

rro

sio

n R

ate

(u

m/y

r)


0

5

10

15

20

25

30

35

40

45

2/14

/00

3/10

/00

3/14

/00

3/16

/00

7/5/

00

11/1

6/00

2/13

/01

4/24

/01

5/21

/02

11/1

6/05

Test Date

Co

rro

sio

n R

ate

(u

m/y

r)

Corrosion Rate Values0

1

2

3

4

5

6

7

2/14

/00

3/10

/00

3/14

/00

3/16

/00

7/5/

00

11/1

6/00

2/13

/01

4/24

/01

5/21

/02

11/1

6/05

Test Date

Co

rro

sio

n R

ate

(u

m/y

r)


Summary

• Inhibitor effectiveness is very influenced by the state of the reinforcement at time of treatment and the hostility of the chloride environment.

• This inter-relationship makes it difficult to specify precise limits on the effectiveness window but qualitative guidance is proposed.

• Optimal use of inhibitors may be as part of a proactive maintenance strategy and the earlier they are applied the better.

• The use of corrosion monitoring is invaluable in managing such repair strategies

Further Information

• SAMARIS Report D21• Field Studies

• SAMARIS Report D25a• Guidance on use of surface-applied

corrosion inhibitors

Advances in rehabilitation of highway structuresDiscussion, Summary and PerspectivesProf. Eugen BrühwilerMCS/EPFL

… improving the performance !

• apply advanced structural assessment to limit interventions

• improve the structure (not just repair it)• reduce the duration of interventions • reduce life-cycle costs (without increasing the

cost of intervention)

Achieving improved performance …through:• education motivation• applications demonstration• guidelines regulation

Table of contents M. McKenzie Guidelines on the selection of innovative techniques for the...

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