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

1. Organiser: Hong Kong Concrete Institute Co-organisers:The Hong Kong Institution of Engineers (Building Division)Hong Kong Concrete Repair AssociationDepartment of Civil and Structural Engineering, The Hong Kong Polytechnic University Use of Vapour Phase Corrosion Inhibitor Capsules for Long Term Protection of Repaired Reinforced Concrete StructuresMr. Brian Davies, XQ International, Bristol, UK Seminar on Concrete Damage Assessments, Concrete Repair and Concrete Mix Technology

2. 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) Seminar on Concrete Damage Assesments, Concrete Repair and Concrete Mix Technology, HK Concrete Institute, HK PolyU 5 Feb 2010

3. 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 Seminar on Concrete Damage Assesments, Concrete Repair and Concrete Mix Technology, HK Concrete Institute, HK PolyU 5 Feb 2010

4. VPCI capsule is inserted into 25mm holes which are drilled in the structure to be protected. Vapour Phase Corrosion Inhibitors How they work Seminar on Concrete Damage Assesments, Concrete Repair and Concrete Mix Technology, HK Concrete Institute, HK PolyU 5 Feb 2010

5. 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. Vapour Phase Corrosion Inhibitors How they work Seminar on Concrete Damage Assesments, Concrete Repair and Concrete Mix Technology, HK Concrete Institute, HK PolyU 5 Feb 2010

6. 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. Do Vapour Phase Corrosion Inhibitors Protect Steel?Simple Nail Test Seminar on Concrete Damage Assesments, Concrete Repair and Concrete Mix Technology, HK Concrete Institute, HK PolyU 5 Feb 2010

7. Do Vapour Phase Corrosion Inhibitors Protect Steel?Further Evidence May 17, 2007 May 22, 2008 Seminar on Concrete Damage Assesments, Concrete Repair and Concrete Mix Technology, HK Concrete Institute, HK PolyU 5 Feb 2010

8. Do Vapour Phase Corrosion Inhibitors Protect Steel?Laboratory Tests Steel in Concrete2% calcium chloride, 6 months duration Seminar on Concrete Damage Assesments, Concrete Repair and Concrete Mix Technology, HK Concrete Institute, HK PolyU 5 Feb 2010

9. 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) Seminar on Concrete Damage Assesments, Concrete Repair and Concrete Mix Technology, HK Concrete Institute, HK PolyU 5 Feb 2010