Treating corrosion in reinforced concrete structures using galvanic - PowerPoint PPT Presentation

Treating corrosion in reinforced concrete structures using galvanic anodes Presented by: Gareth Glass Concrete Preservation Technologies Your Organisation Logo here

Agenda  Causes & Implications of Corrosion  Influential Factors  Repair Solutions  Case Studies

Corrosion of Steel in Concrete  Concrete is alkaline  Protective passive film is formed on steel  The passive film can break down causing the steel in concrete to corrode

Why does steel in concrete corrode?  Sea water  Chloride accelerators ACID  Atmospheric carbon dioxide

Corrosion of Steel in Concrete Corrosion is an electrochemical process Concrete Cl - Cl - H 2 O OH - O 2 HCl HCl HCl HCl HCl HCl Passive Film HCl HCl e - ANODE CATHODE Fe 2+ Steel • Current flows • Products are expansive Co rro sio n spre ads side ways

Reinforcement Corrosion Concerns a) Falling objects – Public safety at risk b) Structural w eakening – Public safety at risk c) Aesthetic issues d) Loss of structure value Manor Road Bridge, Highway Overpass Collapse in 2006 M6, UK, 2014 due to corrosion of steel

Concrete Corrosion Testing Concrete corrosion testing; - Visual inspection and assessment - Delamination survey - Cover depth meter survey - Carbonation depth - Dust sampling (Chloride profiling) - Steel potential survey Car Parks Buildings Bridges Marine

Corrosion Repair Solutions  Do nothing  Patch Repair  Electrochemical Treatments  Monitor

Concrete Patch Repair  Basic option  Short term solution - On-going corrosion - Incipient anode

Zinc/Steel Anodes Steel bar passive in chloride free concrete Zinc/ Steel anodes in chloride containing m ortar Zinc/Steel Anode I 120 Steel Rebar Cl - Contaminated Mortar Bulk Concrete 120 600

Anode response to outdoor climate 20 Anode Current (mA/m 2 ) (mm) (˚C) Temperature 10 Rainfall 0 150 55 100 Steel Anode 50 0 55 60 65 70 75 Time (Days)

Anode response to outdoor climate 700 Anode Current Density (mA/m 2 ) 600 500 Zinc Anode Steel Anode 400 300 200 100 0 55 60 65 70 75 Time (Days)

Corrosion of Steel in Concrete Corrosion is an electrochemical process Concrete Cl - Cl - H 2 O OH - O 2 HCl HCl HCl HCl HCl HCl Passive Film HCl HCl e - ANODE CATHODE Fe 2+ Steel

Galvanic anode operation Cl - Cl - Zn 2+ OH - OH - O 2 O 2 HCl HCl HCl HCl HCl HCl HCl HCl e - e - CATHODE ANODE Fe 2+ 1 st Generation: Galvanic anodes in patch repair to stop anodes on steel

Galvanic anode operation Cl - Zn 2+ Cl - OH - OH - O 2 O 2 HCl HCl HCl HCl HCl HCl HCl HCl CATHODE e - e - ANODE Fe 2+ 2 nd Generation: Galvanic anodes in parent concrete to stop anodes on steel

Patch Repair Galvanic Protection for Concrete Repairs  Simple installation  Maintenance free  Proven technology  Typically 15 - 20 years lifetime  Smaller anode  Closer to area of need  Performance not degraded by high quality repair materials

Patch Repair Galvanic Anode Installation on a Car Park in Letchworth, UK 1. Drill a hole and 2. Insert the anode 3. Fix anode wire to apply Mortar steel and apply repair mortar

Electrochemical Treatment Hybrid Anode Technology  Extends life by 30 to 50 years  Simple installation with less concrete breakout  Low maintenance  Innovative dual technology  Cost-effective  Performance can be monitored  Conforms to international standard ISO 12696: 2012

Electrochemical Treatment Hybrid Anode Technology Brief Impressed Current: Restore pH at acidic pits Galvanic Protection: Maintain pH Galvanic Anode Cl - Concrete OH - OH - O 2 Oxide Film HCl Pit Re-alkalisation Steel

Electrochemical Treatment Hybrid Anode Installation at Crystal House, Preston, UK 1. Drill a hole and soak it with water 2. Connect anode to the wire 3. Apply Mortar 4. Install the anode 5. Apply repair mortar

Monitoring Why monitor? Section 8.6 and Galvanic Anodes: “If a corrosion risk is identified then steps shall be taken to increase the protection current, by supplementing the galvanic anode system, to minimize this risk.”

Monitoring 0 - 100 Potential (mV vs SCE) - 200 - 300 - 400 - 500 - 600 - 700 0.1 0 1 10 100 1000 Corrosion Rate (mA/m²) Corrosion Science, 1991

Case Histories Grosvenor Car Park, UK PROBLEM • Visible cracking and spalling to deck areas and columns SOLUTION • Galvanic Anode • Independent assessment of sacrificial anode performance • Car park in use during repair work

Case Histories Grosvenor Car Park, UK Close Interval Potential Mapping -450 -400 -350 Potential Change (mV) -300 -250 -200 -150 -100 -50 0 0 200 400 600 800 1000 1200 1400 Distance from Patch (mm)

Case Histories Grosvenor Car Park, UK

Case Histories Kyle of Tongue Bridge Beams, UK PROBLEM  Chloride induced corrosion SOLUTION  Targeted application of Galvanic and Hybrid anodes  Low maintenance and long-term solution  On-going monitoring of steel condition

Case Histories Kyle of Tongue Bridge Beams, UK

Case Histories Kyle of Tongue Bridge Beams, UK

Case Histories Kyle of Tongue Bridge Beams, UK

Case Histories Kyle of Tongue Bridge Beams, UK Corrosion rate comparison Corrosion Corrosion Span Date Rate Date Rate (mA/m 2 ) (mA/m 2 ) Span 8-9 01/9/2011 39.9 12/1/2012 0.74 Span 9-10 02/9/2011 6.03 12/1/2012 1.19 Span 12-13 1/10/2011 2.47 12/1/2012 0.54 Span 16-17 21/7/2011 6.8 12/1/2012 0.86

Case Histories Laverock Hall Bridge, UK PROBLEM  Chloride induced corrosion SOLUTION  Targeted application of Hybrid Anode technology  Low maintenance and long-term solution  On-going monitoring of steel condition

Case Histories Laverock Hall Bridge, UK -100 -100 -100 4 4 4 Corrosion Rate (mA/m 2 ) Corrosion Rate (mA/m 2 ) Corrosion Rate (mA/m 2 ) Ste e l c o rro sio n po te ntials and Ste e l c o rro sio n po te ntials and Potential (mV vs SCE) Potential (mV vs SCE) Potential (mV vs SCE) rate s in a 2006 b ridg e installatio n rate s in a 2006 b ridg e installatio n -150 -150 -150 3 3 3 -200 -200 -200 2 2 2 Potential Potential Potential -250 -250 -250 1 1 1 Corrosion rate Corrosion rate Corrosion rate -300 -300 -300 0 0 0 0 0 0 0 100 100 100 100 200 200 200 200 300 300 300 300 400 400 400 400 500 500 500 500 600 600 600 600 700 700 700 700 Time (days) Time (days) Time (days)

Case Histories Laverock Hall Bridge, UK 0 -50 Potential vs Ag/AgCl (mV) -100 -150 -200 -250 -300 -350 0 1 2 5 6 7 8 Time (Years)

Case Histories Whiteadder Bridge, UK PROBLEM  Chloride induced corrosion SOLUTION  Targeted application of Hybrid anode technology  Low maintenance and long-term solution  On-going monitoring of steel condition

Case Histories Whiteadder Bridge, UK -100 30 -150 25 -200 Couple Potential v. Ag/AgCl (mV) Anodes Active Anodes -250 >100mV polarisation 20 Passive Galvanic current (mA) -300 -350 15 Galvanic potential -400 Galvanic current 10 -450 Increased Current x10 -500 5 -550 -600 0 4.80 5.00 5.20 5.40 5.60 5.80 6.00 6.20 6.40 Time (years)

Case Histories Swimming pool at Leisure Centre Durham, UK PROBLEM  Visible delamination and spalling  Low budget SOLUTION  Iterative testing & evaluation  Targeted application of Galvanic Anode

Case Histories Birmingham New Street, Network Rail, UK PROBLEM  Visible cracking & spalling to main beams  Short timescale  To avoid use of permanent power supply SOLUTION  Visual assessment & evaluation  Hybrid anode technology

Case Histories Dagenham Jetty, UK PROBLEM • Chloride attack affecting structural integrity • Avoid the use of permanent power supply SOLUTION • Visual assessment & evaluation • Hybrid anode technology • The structure remained in use • No requirement for permanent power supply • Minimal whole life care cost

Case Histories Fuel Loading Facility, Shell PROBLEM • Sea water affecting structural integrity • No external power allowed • Structure to remain in use at all times SOLUTION • Visual assessment & evaluation • Galvanic anode system • Structure remained in use • No permanent external power supply

Case Histories Power plant, South Africa Koeberg Nuclear Power Station

Case Histories Housing, Saudi Arabia CPT corrosion protection products are widely used in environments with hot temperatures which can rapidly accelerate the corrosion process

Case Histories Lighthouse & Saline Water Containment Tank, Australia

Summary  Corrosion is an electrochemical process  Galvanic and Hybrid technologies provide valid strategies to manage corrosion in accordance with international standards  Benefits include:  Limit disruption during application  Targeted to area of need  Increase service life  Reduced breakout