The fundamental application of " cathodic prevention " of steel reinforcement in concrete was ideated and developed by Professor Pietro Pedeferri. It was successfully applied since 1989 in Italy on Viaduct St. Nicholas I of the highway Rome - Aquila - Teramo and in 1996 in the western underbroadwalk of the Sydney Opera House. Over the past 20 years it has spread throughout the world and particularly in Northern Europe, Middle East and Australia being recognized as the most reliable technique to combat corrosion for new buildings and infrastructure where reinforced concrete is exposed to possible contamination from chlorides. This memory is a review of some of the most significant industrial cases reported in the international literature. Durrat Al Bahrain and the NAKILAT shipyard in Qatar are two recent projects developed in the Middle East. Cathodic Prevention of West Swanson Dock in Melbourne was the largest project completed in Australia in the last decade. Other significant experiences in China and North Africa are a sign of the vitality of this technique in the developing countries.

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SPECIALTIES & NEW APPLICATIONSPOOLS & ELECTROCHLORINATIONELECTRONICS & SURFACE FINISHINGCHLORINE & CAUSTIC INDUSTRY
Cathodic prevention of steel
rebars in concrete: the
international outlook.

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What have great projects in common?

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Cathodic Prevention
Pedeferri Diagram

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Cathodic Prevention
Limited embodied energy; small cathodic current.
Extensive Reference in International Standard EN ISO 12696:2012 “Cathodic
Protection of Steel in concrete”
ANNEX A
Concrete protection GJ/m2
Polymer Modified Cementitious Coating 0,015
Acrylic coating 0,025
Cathodic Protection (installed) 1,7
Cathodic Protection (per year) 0,004
PrevC (installed) 0,04
PrevC (operation per year) 0,002

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St. Nicola I Viaduct – A24 (1989)
De-icing salts

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St. Nicola I Viaduct – A24 (1989)
Continuous structure: 11 spans
Total surface to be protected: 5600 m2
Prefabricated concrete segments post-tensioned with high
strength steel cables.
Hydrogen embrittlement: at pH > 12 potentials more
negative than -950 mV (SCE)

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St. Nicola I Viaduct – A24 (1989)
Steel protection current density to a depth of 40cm: 10mA/m2
Anode layout: Titanium MMO Net single, double, triple
Small anodic zones (100m2) with 4 current distributors
Reference electrodes: Ag/AgCl and Titanium MMO close to
post-tensioned cable and rebar
Remote monitoring control unit

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St. Nicola I Viaduct – A24 (1989)
CP system performances
Average current density: 6mA/m2
IR drops in the anode net each zone < 50 mV
Average polarization 200 mV
Tensioned cables potential >> -900mV

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Sydney Opera House (1996)

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Sydney Opera House (1996)
Prevent corrosion of new precast elements of the substructure of western
under broad-walk
68 Zones: geometry + environment (tidal, submerged and atmospheric)
LIDA® GRID: flexibility of current density and Titanium MMO rods
Total concrete area of CPrev application: 742 m2
Protection current density: 10 mA/m2
80 Reference electrodes: Ag/AgCl, Ti MMO, Zn

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Sydney Opera House (1996)

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Sydney Opera House (1996 e 2005)
Protection criteria: 100 mV potential decay in 24h (atmospheric and splash
zones structures)
Instant OFF potential: > -900 mV < – 1100 mV Ag/AgCl/0,5M KCl as per
AS2832.5 (concrete elements submerged in SWT)
System energized in 1996: Potential well above the limit for overprotection in
A-frames (post-tensioned steel)
After 10 years of operation: no visible deterioration, spalling or delamination
Protection current density: 2-5 mA/m2
17% faulty reference electrodes (most Ag/AgCl)

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Swanson Dock West (2008-2009)
1 Km
Melbourne’s
Main container
Port
3 CP systems
Construction in
stages: 1974-1988
4 berths

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Swanson Dock West (2008-2009)
Cathodic Prevention applied to the new ship fender (500m) of berths 1
and 2 in the splash and tidal zones.
Heavily chloride contaminated: cracking and spalling.
600 mm

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Swanson Dock West (2008-2009)
Fender beam sections reconstruction. CP rev applied in 30 locations: 3,5m
in length up to 0,5m from the base
Anodes: MMO titanium mesh ribbon anodes applied on insulating spacers
Protection current density (conservative): 20 mA/m2

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Swanson Dock West (2008-2009)
Trial system: 2 anodes on each face and 3 on the base 3,5m long
Reference electrodes: 2 embedded in concrete + external (250mm grid)
24h Depolarization 100 mV : only 40% of the grid points
72h Depolarization 100 mV: 90% of the grid but not at the extremities
0,5 m

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Swanson Dock West (2008-2009)
New design: additional anode on each side of the beam 500mm up from the base
+ additional transverse anode at the ends of the 3,5m beam section
30 reconstructed areas with new design: 6 zones 5 areas each
Overall capacity (sized for future expansion): 30 A
Since Jan 2009 energized and succesfully polarized achieving the 100 mV decay
criterion

18. Durrat Al Bahrain (2007)
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Durrat Al Bahrain (2007)
13 islands
13 bridges l: 3,5 km
2000 villas
3000 apartments

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Durrat Al Bahrain (2007)
T water: 35°C
Salinity: 37-39 g/l
Bridges height:2m
Lifetime: 50 years
Rebar corrosion
chloride
contamination
Cost CPrev:
2.130.000 USD
Cost stainless
steel (304)
22 Millions USD

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Durrat Al Bahrain (2007)
Design Life 50 years
Anode type MMO coated titanium ribbon
mesh
Cathode current density 5 mA/m2
Max Anode current
density
110 mA/m2
Protection Criteria 100 mV decay or -720 mV vs.
Ag/AgCl
Max zone size 3A
Power/Monitoring System Fully remotely controlled and
monitored

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Durrat Al Bahrain (2007)
Name Length Total N°
Atoll Bridges 162 m 6
Hotel Bridge 680 m 1
Ring bridges 518 m 2
Ring bridges 210 m 4

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Durrat Al Bahrain (2007)
Max Zone Size: 3 A
4 pre-cast decks + 4/6 pile heads
Bridge end: 1 abutment, 2 pile heads + 2/4 pre-cast units
Element Protection Current
Pre-cast deck unit 662 mA
Exposed section of abutments 287 mA
Piles above casing
(Pile Head)
31 mA

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Durrat Al Bahrain (2007)

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Durrat Al Bahrain (2007)
Reference electrodes:
embeddable Ag/AgCl
Recorded native and
instantaneous Eoff
potentials after 1h up to 24h
Good potential shift in 3-4 h
Homogeneity of shifts and
even protection

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Durrat Al Bahrain (2007)

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Nakilat – Qatar (2006 -2009)
54 ships
610 Mil US$

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Nakilat – Qatar (2006 -2009)
2 Km quays
and piers

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Nakilat – Qatar (2006 -2009)
54 cellular caissons in reinforced concrete
Overall dimensions: 36 m x 36 m x 11 m; weight 4000 ton
CPrev to grant 50 years design life in the Persian Gulf
MMO mesh ribbon anodes for splash and atmospheric zone

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Tangiers-Med Port (2005 -2012)

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Tangiers-Med Port (2005 -2012)
Tangier Med: 2007 first multi-purpose wharf
2008 second terminal 3,5 Millions container py
Tangier Med II: 2012-2015 2 new terminals 2800m long
5 Milions container
Larger port in the Mediterranean Sea

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Tangiers-Med Port (2005 -2012)
Primary and secondary breakwaters builded by consortium
Bouygues-Bymaro-Saipem to protect the port
Water depth > 20m zone: 40 precast reinforced concrete caisson
built on land then placed in the seawater and completed with
the second phase of concreting

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Tangiers-Med Port (2005 -2012)
1 caisson = 4 cells 28mx28mx35m h, weight 7900 ton
550 ton of steel and 3000 m3 of concrete
CPrev in tidal and splash zone to stop corrosion induced by chlorides
Grid system with MMO Titanium mesh ribbon

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Hangzhou Bay Bridge (2004-2005)
36 km
Opening:
14/06/2007
Among the
ten longest
trans-oceanic
bridges

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Hangzhou Bay Bridge (2004-2005)

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Xia-Zhang Bridges (2011-2013)
Total length North
Branch: 6392 m
L cable-stayed: 1290m
720m main span
6° world-wide long
cable-stayed combined
with steel and concrete

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Xia-Zhang Bridge (2011-2013)
Cprev 4 main pylons and 4 piers
Tidal and splash zone: 13100m2
Anode: MMO Ti activated mesh ribbon
applied on the rebar with concrete spacer

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Louvre Abu Dhabi, UAE (2013-2015)
On Saadiyat Island due to open end of 2015
Cprev installed on all exposed surfaces of the reinforced concrete
sub-structure up to a height of +3.45m

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Louvre Abu Dhabi, UAE (2013-2015)
Cprev system for a design life of
100 years
Anode: MMO Ti activated mesh
ribbon installed in the screed
to protect rebar in the lower
reinforcement of the strip
footings, ground beams and
slabs
Fixed to the rebar cage using
plastic clips for all other
surfaces

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Conclusions
Cathodic Prevention, conceived by Prof. Pietro Pedeferri, has
proven to be a viable technique to stop corrosion of steel
reinforcement in concrete.
From the first trials in the mid-’80s this idea has evolved over the
course of thirty years becoming a well established technique to
preserve structures subject to corrosion induced by chlorides
contamination.
Several aspects of cathodic prevention have been incorporated in
international standards such as ISO 12696:2012 and AS2832.5-
2008.
The diffusion of the technology from the US and Europe to
Australia, Middle East, China and North Africa is a sign of the
relevance of this idea in the corrosion prevention global
market.

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Thank you for your time
Q&A