7th Australian Small Bridges Conference

Extending the Life, Serviceability & Durability of the Sylvania Waters Concrete Bridges

Ian Godson Managing Director

Infracorr Consulting Pty Ltd

Infracorr Consulting

• Specialist Consultants in the Repair and Preservation of Infrastructure

• Investigation & Condition Reporting

• Design & Specification of Repair Systems

• Tender Assistance

• Supervision of Repairs

• Commissioning & Ongoing Monitoring

• Design for Durability (New Structures)

Sylvania Waters Estate BridgesBuilt in the late 1960’s, these structures are located in the Sylvania Waters estate in Sutherland Shire of NSW, approximately 15 km from Sydney Airport.

The six bridges generally conform to the following arrangement:

• Single span road bridges

• 3 to 8 m long; 12 to 15 m wide

• Precast driven sea-wall panels forming abutments

• In-situ capping beams

• In-situ reinforced concrete deck slab

Visual Condition of the BridgesThe bridges were in a poor visual condition including Cracking, Delamination & Spalling

• Soffits

• Mostly Sound

• Localized Delamination & Spalling

• Capping Beams

• Significant Cracking & Rust Stains

• Delaminated & Spalling Areas

• Failed Previous Patch Repairs

• Precast Seawall Panels

• Mainly Sound

• Some cracking

• Spalling Sections on some Panels

Investigation of Concrete Distress

• Delamination/ Spalling

• Carbonation depth

• Chloride concentration with depth

• Cover depth (the time fuse)

• Half cell potential (equipotential)

• Corrosion rate

• Concrete resistivity

• Electrical continuity

Stages of Reinforcement Corrosion in Concrete

initiation phase timepropagation phase

amo

un

t of co

rrosio

n

2

3

4

collapse

1

crackingdepassivation

spalling of cover

initiation phase timepropagation phase

amo

un

t of co

rrosio

n

2

3

4

collapse

1

crackingdepassivation

spalling of cover

Corrosion Mechanism of Reinforced Concrete

Ionic current

CorromapCorrosion Rate & Half Cell Potential

70 mm

PSIONWork About

Reinforcement

Guard ring

Counterelectrode

Ag/AgClReferenceelectrode

EQUIPMENT

Belgrave Esp BridgeCapping Beams• Significant cracking & rust at base• Failed Previous Patch repairs• Half Cell- ACTIVE Corrosion 90%• Chloride 0.54% Cl wt Concrete (10 Times Critical of 0.05%)• Corrosion Rate –VERY FAST (17mA/m2) Spall within 5 yearsSoffit• Sound most areas (Spalling 5% area)• Half Cell – Majority Passive• Only 10% Active Corrosion here, but average 50%• Chlorides 0.03%- NON Critical to 0.2% Critical• Corrosion Rate- Slow Passive; Fast in localized areas

Equipotential Map (mV vs CuCuSO4) of Belgrave Esplanade Bridge - North West Beam

NE← →SW

Resistance Map (kOhm) of Belgrave Esplanade Bridge - North West Beam

NE← →SW

Equipotential Map (mV vs CuCuSO4) of Belgrave Esplanade Bridge – Soffit adjacent North West beam.

NE← →SW

Resistance Map (kOhm) of Belgrave Esplanade Bridge - Soffit adjacent North West beam.

NE← →SW

Richmond Ave BridgeCapping Beams• Significant cracking & rust staining• Half Cell- ACTIVE Corrosion 100%• Chloride 0.23% Cl wt Concrete (5 Times Critical of 0.05%)• Corrosion Rate –VERY FAST –Spalling within 5 years

Soffit (Precast)• Sound • Half Cell –Passive• Chlorides 0.02%- NON Critical• Corrosion Rate- Slow Passive

Equipotential Map (mV vs CuCuSO4) of Richmond Avenue Bridge - South West Beam

SE← →NW

Resistance Map (kOhm) of Richmond Avenue Bridge - South West Beam

SE← →NW

Equipotential Map (mV vs CuCuSO4) of Richmond

Avenue Bridge – Soffit Beam near SE side

SW← →NE

Resistance Map (kOhm) of Richmond Avenue

Bridge – Soffit Beam near SE side

SW← →NE

Seawall Panels• Typical Panel Half Cell indicates active corrosion- Caution with wet

elements as results deceiving

• Corrosion Rate Moderate to Fast – Spalling in 5-10 years

• Chloride levels Very High (0.3% Cl/wt concrete) 8 x Critical

• Panels corroding in top 1m but at slower rate than capping due to high moisture levels

Bridge Condition SummaryBRIDGE SPAN/

WIDTH

(m)

Seawall Panels Capping Beam Slab Soffit

%

Spalling

%

Corroding

%

Spalling

%

Corroding

%

Spalling

%

Corroding

1 Bogan Ave 3.0/13.0 5 60 40 100 40 80

2 Richmond

Ave

4.0/12.0 4 70 20 100 5 10

3 Warrego

Ave

4.5/14.5 5 50 40 100 5 60

4 Belgrave

Esp

8.0/12.5 10 70 50 100 5 80

5 Bellinger Pl 3.5/14.0 5 55 20 75 10 40

6 Tuross Ave 3.5/14.0 10 60 30 100 15 40

Repair Options

• Preventative Coatings (Silane Impregnations)

• Patch Repairs

• Impressed Current Cathodic Protection (ICCP)

• Hybrid CP

The Sutherland Shire Council required a life extension of 30 years for the bridges. Options considered for the repairs included:

Patch Repair (PNG 1992)

Patch repairs • Remove concrete 30mm behind bars• Clean & repair reinforcement• Replace mortar (pour, spray or hand

place)

Structurally InvasivePoor Durability Don’t address corroding areas in sound

concrete

Impressed Current Cathodic ProtectionUses a small, permanent DC current to virtually stop the corrosion process

Cl-

Duct & strand

Cl- Cl-Cl-

Morell Bridge – Melbourne 1995Earth filled bridge built 1890’s

•12 No. soil anodes

•Manual control system

•Institute of Engineers Award

Soil anodes

Beam Underside600m long x 3m wide x 100% delaminationFull extent of concrete removal for CP

Anode Installation-Strip Ti Anodes

VicRoads Deep Creek BridgeTooradin, Gippsland Highway

• ICCP Internal Anodes (central)

• Remote Monitoring

• Cardinia Creek Bridge Similar design

Sydney Opera House

Cathodic Protection Repair

Sydney Opera House ICCP Based Repairs1995 - 1996

Grid

anodesWater Anodes

ICCP Transformer Rectifier

• Monitor and adjust 6 monthly

Hybrid CPShort Term Impressed Current, Long term Galvanic

Hybrid CP System

• Hybrid CP System

• Anode made of Zinc Alloy

• Installed in 30mm dia holes

• Hole filled with special mortar

• Connected with Ti wire to small junction box

Bridge Beams Hybrid 2013-14

Hybrid • System is powered for 1 to 2

weeks

• 6V to 12 V DC power (small T/R)

• Cables & Power Supplies then removed

• Anodes connected to rebar in JB

• Anodes maintain protection-galvanic (around 1-2mA/m2)

Galvanic Currents-5

-4

-3

-2

-1

0

1

2

0 20 40 60 80 100 120 140 160

Cu

rre

nt

in m

A/m

2 s

tee

l

Time (Hrs)

LIP Galvanic Phase Current Logging - Pile GCurrent per sqm steel

Lower

Upper

Anode Life Calculation• Anode Life Calculation included impressed current &

Galvanic current

• Used average Galvanic Current after 1 month (ie no seasonal effects considered)

• Anode Life in Tidal Zone considerably less than upper zone (REDESIGN LOWER ZONE ANODE ARRANGEMENT?)

Zone Life

(average)

(years)

Range

(Years)

Min Life

Pile Years

Upper 50.3 20.3 - 97.5 L 20.3

Lower 30.4 14.8 – 52.9 A 14.8

Queensland Box Culvert• Precast Box Culvert Conveyor Tunnel

• Significant spalling (Chloride)

• Half Cell Mapping

• Hybrid Anodes to actively corroding zones

Main Roads Queensland

• Cairns Box Culverts with significant Spalling• Corromap Half Cell Survey• Hybrid Anodes to actively corroding areas• Silane coatings in sound concrete areas

Dampier Dolphins - Hybrid

• Hybrid anodes protect 3 dolphins

Dampier Salt Dolphins• Concrete Repair & Hybrid CP designed & supervised by Infracorr

Princes Wharf . Repair Project Nov 2013-Mar 2014 • Continuity Established in Hydro Holes

• Hybrid Anodes Installed (low voltage )

• Corroded Strand Cut Out

• Concrete Repair (no strand replacement)

• Carbon Fibre Laminates to Beam Soffit

Sylvania Waters BridgesRepair System Selection• Time related repair costs were evaluated (30 years)

• Repeated Patch repairs most economical initially, but most costly over 30 years

• ICCP Relatively costly install, with high annual monitoring & maintenance costs

• Hybrid CP

• Reduced installation costs compared to ICCP

• Reduced Monitoring & Maintenance compared to ICCP

0

500

1000

1500

2000

2500

3000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

$K

Years

Sylvania Waters BridgesForecast Cost vs Repair Type over 30 years

Patch Repair ICCP Hybrid CP

Hybrid CP DesignHybrid CP designed to protect:

• Pile Wall (Top metre)

• Capping Beams entire length

• Soffit Slabs ( Selected locations actively corroding)

Hybrid CP Design• Typical design for Capping Beams & Top of Pile Walls

• Capping Beam, 2 anodes high at 350mm spacing

• Pile wall, 9 anodes at 300mm spacing

• 1 Junction Box

Hybrid CP Design- Soffit

• Hybrid Anodes at 300mm to 350mm Spacing

Repair Phase

• Tender to Licensed Hybrid CP contractors

• Awarded February 2014 (Marine & Civil)

• 2 Bridges at a time

• Access by hung platforms

• QA by Infracorr

Installation Hybrid CP• Concrete Removal by Small Jackhammers

• Capping Beam large scale rebar repair

• Anode holes drilled with percussive drills

Repair & Installation

• Some sections of Capping Beams severely deteriorated

• Anode Installation prior to final gunite mortar application

• Soffit spalling breakout required in some areas

• Bulk of soffit anodes installed into sound concrete

Hybrid CP Based Repair• Repair works from March–November 2014

• 2 Bridges at a time (around 3 months each bridge)

• Junction Box only visible sign of CP installation

Finished view of a completed bridge

Junction Box is only visible Hybrid CP component.

Sylvania Waters Bridges Repair• Hybrid CP Based repair selected

• Most economical option over 30 years

• 30 Year design life (likely 50 plus)

• All Seawall panels, capping beams & selected soffits protected

Sylvania Waters BridgesConclusion• Always Investigate to determine extent of corrosion, Not just extent of

spalling• Get in early to maximize prevention options (Coatings)• Consider the lifetime required for the structure repairs• Choose repair options based on most economical treatment for LIFE

Thank You for your attention

Sylvania Waters BridgesConclusion• Always Investigate to determine extent of corrosion, Not just extent of

spalling• Get in early to maximize prevention options (Coatings)• Consider the lifetime required for the structure repairs• Choose repair options based on most economical treatment for LIFE