Cathodic Protection of Concrete Structures

1. Systems By SRCP Cathodic Protection of Concrete Structures

2. Cathodic Protection Systems Conductive coating Surface mounted ribbon anode Mesh in precast stick-on shapes Ti wire in acid resistant cylinder for embedment Zinc sheet with self adhesive activator Rolled ZLA grouted in drill hole ZLA block for embedment in repair ZLA block in precast container Remote monitoring and control • Impressed Current • Zebra • Cassette • CorroDisc Surface Embedded • Sacrificial Anode • ZLA • Roll Anode • GSC Super Anode • Clip On Anode • Monitoring and Control • Camur

3. Reinforcement Corrosion Process • An area of reinforcement becomes anodic due to chloride or carbonation ingress. • Corrosion is stopped if: • Oxygen at cathode stopped • Full immersion • Small cathode • Resistance of electrolyte high • Low due to chloride & water • Electrons supplied from alternative anode • Anodic and cathodic reaction are critical to how the cell works.

4. What is Cathodic Protection Galvanic Anode • Provides and alternate anode to prevent reinforcement corrosion • Sufficient current to ensure protection over all rebar • Determined by code criteria • 100mv decay at 24hrs • Eliminates need for breakout of sound but contaminated concrete • Eliminates structural problems • Reduced noise and dust Current C u r r e n t F l o w

5. Impressed Current Cathodic Protection • Powered system so no limit to the level of protection • Over protection • Prestress particular concern • Acidification around anode possible • Under protection • System failure • Protection requirements change • Reliable and total protection when maintained • Detailed design • Expert commissioning • Regular monitoring • High life cycle cost • Particularly for small projects

6. Zebra US Patent 6855199 B1 2005 • Water soluble silicate carrier • penetrates and forms micro-crystalline bond with concrete • Filled graphite particles Zebra Anode Zebra PDR Tape Zebra PDR Bond Coats Wearing Surface Concrete Layers of a Zebra System for the wearing surface of a car park deck

7. ZebraProjects Building facade Car park capillary rise zone • 400+ projects • Light weight • Conventional painting skills • Rapidly applied • Decorative • 20+ year life Applications • Building facades, balconies and slabs. Balcony soffits Car park slab

8. Cassette • Ribbon anode in a surface mounted inert carrier. • Ribbon anodes are a proven ICCP system except acidification of slotted systems can cause failure after 15-20 years. • Cassette overcomes acidification issues.

9. Cassette • Proven Elgard 150 ribbon anode. • Surface mounted in own tray. No grinding or shotcrete. • Inert system. Acidification around anode not an issue. • Simple to install. Just bolt on (stainless steel or fibre glass). • Doesn’t add significant weight. • MMO coated titanium, life typically 50 years. Applications • Where aesthetics not critical, e.g. tanks, car parks • Confined spaces, e.g. basements, tunnels • Projects where wet exposure, wharf and bridges splash zones

10. Cassette Projects Car park capillary rise area Pipe tunnel, poor access Prestressed bridge T-Roffs Brdige deck soffit Cast insitu bridge beam Roof of Tunnel Soffit

11. CorroDisc • MMO coated titanium mesh in a silicate based mortar • Mesh • long term proven performance • 50 year life • Mortar • resistant to strong acids • Permeable to water vapour & oxygen • Real CP • Satisfies the 100mV criteria • Convenient testing • Use individual Corrodiscanodes CorroDisc R – 60x400mm wide surface applied anode typically applied in line to give 3-4 anodes/m2 CorroDisc 125 – 125mm diameter circular surface applied anode typically applied on a rectangular grid to give 4-8 anodes/m2 MMO coated titanium mesh

12. CorroDisc • Easy & economic installation • Surface applied • Avoids grinding, drilling or embedding the anodes in the structure • Local surface preparation only • Flexible anode placement • Reasonable appearance once coated • Not suited to wet areas Pressing CorroDisc 125 onto surface Pressing CorroDisc R onto surface

13. Camur Monitoring and Control Computer • Remote control & monitoring essential for ICCP • Power supply units 3 or 8amp • Single bus cable • Power control • Power monitoring • Half cell monitoring • Integral computer logs data • Data accessed remotely • Data collection software • Web viewing software Transformer Bus interface Rectifier 1 zone system (Available for control and monitoring of trial areas).

14. Camur 220/240V Power Supply • Camur System • IP box • Computer • Transformer • Fix Volts • Transformer • Bus Interface • Light/fan/heater • Fuses/sockets • Connectors • Software • Web Site 3 zone system with all anode beds in same location. Concrete Structure

15. Camur • Components sold individually • Computer • Transformer • Fix Volts • Transformer • Bus Interface Right: 3 zone system where anode beds separated. Note wireless link of bus cable. Concrete Structure Working systems. 2 Zones 3 Zones

16. ZLA Range of Sacrificial Anodes • High output for true cathodic protection • Simple to install; limited wiring, no power source • Doesn’t add significant weight. Decorative after coating. • Low design; installation and monitoring costs • Zinc consumed, life typically 20 years Applications • Low cost or limited life projects • Applicators not expert in cathodic protection • Holding repairs • Prestressed items

17. Cathodic Protection vs Prevention A small potential shift gives cathodic prevention, i.e. a high chloride corrosion threshold for cathodic steel. Use low output anodes for incipient anode protections. A large potential shift gives cathodic protection, i.e. immunity from corrosion for active steel. Use high out put anodes (ZLA range) for true CP and no breakout. SACP systems must provide 100mv 24hr potential decay criteria

18. Cyclic Voltametric Testing • Standard electrode test procedure • Cycle voltage and measure current • Zinc Activator Paste (ZAP) optimised by CVT trials ZAP output LiOH output Test system set up Intersection of steel and anode tests gives polarisation expected from anode

19. Zinc Layer Anode (ZLA) Roll of ZLA as applied to the surface of concrete to provide full CP meeting 100mv criteria • Zinc in contact with concrete passivates • Activator applied to zinc keeps it active and ensures continuous cathodic protection • Reactions at the anode / activator interface critical • Zinc chloride formed with ZLA anodes gives high output and long term performance • Anodes lead to true CP with meeting 100mv 24hr decay criteria Roll Anode and GSC Super Anode derived for ZLA and both give CP meeting 100mv criteria.

20. ZLA Projects After ZLA Application After Coating Balconies Walkways Facades Bridges

21. Roll Anode Typical Roll Anode Installation • Drill hole • Depth to move away from extreme fibre stress as required • Insert anode and grout • ZAP for best CP performance • Cement grout for strength Anode string connected to rebar 27mm diameter Roll Anode

22. GSC Super Anode • Bolt to rebar • Cast into repair • Cathodic Protection • No breakout behind bars • Incipient anode protection Anode string connected to rebar 30/20 GSC Super Anode

23. SACP Performance Data • Seineflat Apartments • 100mv criteria met at installationand after 2 years

24. SACP Performance Data • Cape Perpetua Viaduct • 100mv criteria met at installationand after 5 years

25. SACP 1.5m • Stockton Bridge Trial • ZLA provides three times the polarisation of the other SA anodes 1.7m 1 2 3

26. CM2 Rebar Continuity • ICCP and SACP wont work if there is not rebar continuity • CM2 Continuity Tester measures : • resistance at high current (1 Amp) to test connection under load. This is a common failure of connections tested with standard voltmeters. Criteria ≤1ohm) • residual voltage 0.1 sec after the resistance test. Criteria =0V