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Chris Wozencroft

VINCI Construction UK -Technology Centre

Cathodic Protection for Early 20th Century Steel Framed Buildings

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Regent Street Disease

Theory of CP for historic buildings

Practical aspects of application

Guidance and regulation

Examples

Presentations Overview

• 1824 Sir Humphrey Davy reports galvanic CP of ships’ hulls.

• circa 1910 Impressed current CP of buried steel structures.

• late 1940s Impressed current system to pipeline in Africa.

• mid 1950s CP of buried reinforced concrete structures.

• late 1970s CP of reinforced concrete bridge decks in US.

• mid 1980s First building - conductive coatings used as anodes.

• early 1990s Meshless conductive overlay anodes introduced. Desalination and realkalisation in the UK.

• early 1990s CP used to protect steel framed buildings.

• mid 1990s CP using discrete anodes.

• late 1990s Galvanic CP systems.

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Regent Street Disease

(Deansgate Disorder)

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Reliance Building (1895)

Regent Street Disease

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In-fills are generally composed of sand, cement and brick rubble fill.

In-fills

External face

The Mechanism

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The Effect

Cracks at column and beam locations

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• Steel and masonry contact

• No coatings/no adequate coatings

• Porosity

• Carbonation / chloride

• Poor detailing

• Maintenance

• Age

What Went Wrong?

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Traditional Repair Options

• Netting and Fall Protection

• Strapping of Displaced Masonry

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Traditional Repair Options • Masonry Removal and Steel Repair

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Traditional Repair Options

Traditional repair options

• Disruptive

• Costly

• Time-consuming

• Can often be a limited-term solution

• Restoration rather than conservation

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The CP Option

CP for Steel Framed Buildings

• First successful application - Early 1990s

• First sizable structures = 1997

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0 1 2 3 4 5 6 7 8 9 10

VOLTAGE (V)

CURRENT (mA)

0 10 20 30 40 50 60 70

+ -

Direction of Electrical Current

OH- Generation

Monitoring System

H2O

H2O

Reference Cell Anode

CP for Steel in Masonry

Off On

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In the Field

Stone Modillion Block

Embedded cables

and anode ribbon

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Why use CP?

• Heritage - conservation above restoration

• Reduced construction work with shorter programmes

• Long-term solution if properly maintained

• Commercial benefits

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“ The DETR research that Taylor Woodrow has undertaken demonstrates how modern technology can be used to develop sympathetic repair techniques and preventative maintenance consistent with English Heritage's strategy on conservation. We very much support this research” John Fiddler, Head of Architectural Conservation English Heritage

Why use CP?

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The Challenges

• As discrete and sympathetic as possible.

• Involvement of heritage authorities

• Specialist skills (design & on-site)

• Specialist knowledge of construction type

• Availability of as-built information

• Constant survey and testing during installation

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Examples

Blackfriars Bridge Hotel, London

St Andrew’s House, Edinburgh

Joshua Hoyle, Manchester

GMBU, Newcastle

Summit House, London

Paramount House, London

College Street, Dublin

Jam Factory, London

Lion Plaza, London

Marshall Fields, Chicago

Selfridge’s, London

Orient House, London

5 Wigmore Street, London

Boots Building, Nottingham

Indigo Jones

Kenwood House

Waterloo House, Birmingham

Imperial College Boat House

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Examples

Selfridges, Oxford Road, London

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Examples

The (former) Boots Building, Nottingham

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Examples

Grosvenor House Apartments, London

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Examples Orient House, Manchester

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Examples St Andrews House, Edinburgh

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Further Reading

• BSEN ISO 12696:2012

• CPA Technical Note 20

• Historic Scotland TAN20

• CPA Monograph No. 7

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