Seminar on Concrete Damage Assessments, Concrete Repair and Concrete Mix Technology

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Seminar on Concrete Damage Assessments, Concrete
Repair and Concrete Mix Technology

• Use of Vapour Phase Corrosion Inhibitor
  Capsules for Long Term Protection of Repaired
  Reinforced Concrete StructuresMr. Brian Davies,
  XQ International, Bristol, UK

• Organiser Hong Kong Concrete Institute
• Co-organisersThe Hong Kong Institution of
  Engineers (Building Division)Hong Kong Concrete
  Repair AssociationDepartment of Civil and
  Structural Engineering, The Hong Kong Polytechnic
  University

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Corrosion Inhibitors History and Types

• Use to protect steel for over 50 years
• Widely used in reinforced concrete since 1980s
• Types
• Integral or cast in corrosion inhibitors (ICI)
• Surface applied migratory corrosion inhibitors
  (MCI)
• Vapour phase corrosion inhibitor capsules (VPCI)

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Corrosion Inhibitors Do they work?

• Integral or cast in corrosion inhibitors (ICI)
• Yes, but dosage is critical
• Surface applied migratory corrosion inhibitors
  (MCI)
• Yes ?, but highly dependent on porosity and
  correct application rate and method
• Vapour phase corrosion inhibitor capsules (VPCI)
• Yes, but spacing must be controlled

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Vapour Phase Corrosion Inhibitors How they work

• VPCI capsule is inserted into 25mm holes
  which are drilled in the structure to be
  protected.

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Vapour Phase Corrosion Inhibitors How they work

• Three separate inhibitors are released over
  time as a vapour that saturates a given airspace,
  this vapour forms a mono-molecular coating on
  embedded steel. The product travels easily
  through concrete to coat embedded reinforcement
  at a rate of around 1m per week.

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Do Vapour Phase Corrosion Inhibitors Protect
Steel?Simple Nail Test

• 2 nails were sealed in test tubes in 1995, these
  pictures were taken in 2007, the example on the
  left had no VPCI and the one on the right had
  VPCI added.
• The corrosion to the nail on the left is
  significant, the nail on the right shows very
  little corrosion and the tip of the nail is still
  shiny.

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Do Vapour Phase Corrosion Inhibitors Protect
Steel?Further Evidence
May 17, 2007
May 22, 2008
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Do Vapour Phase Corrosion Inhibitors Protect
Steel?Laboratory Tests Steel in Concrete2
calcium chloride, 6 months duration
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Future Testing

• Measurement of VPCI travel in large scale
  laboratory prepared samples and adsorption
  measures using gas chromatography
• Intertek
• Testing to NACE TM 0294-2001, Testing of embedded
  current anodes for use in cathodic protection of
  reinforced concrete, modified for use with VPCI
• The Technology Centre (Taywood Engineering)