Concrete corrosion or 'concrete cancer' as it is sometimes referred to, is actually the corrosion of embedded steel (rebars or concrete reinforcement) within the concrete and not corrosion of the concrete itself. This usually becomes apparent through surface spalling and delamination, caused by the surface of the steel that has corroded, expanding and putting internal pressure on the concrete structure, once the expanded steel builds sufficient pressure, the concrete will crack and rupture. Once this is identified, remedial work needs carrying out to ensure the concrete structure retains its strength. Click here for scientific explanation

 

 

 

Once you have identified rebar corrosion, the building or structure requires surveying to find the most appropriate repair methodology. There are several methodologies that are widely used in the concrete repair industry, either using migrating corrosion inhibitors or cathodic protection. QED manufactures Migrating Vapour Phased Corrosion Inhibitors (VPI's). QED supply these in many forms (gels, tablets, foams, pellets, liquid, tapes) and all work in the same way.

 

 

QED's VPI's work by coating steel with a mono-molecular coating that prevents further corrosion, they do not reverse corrosion but can effectively stop further corrosion for a long period of time. For further information take a look at our Inhibitors Explained section.

 

 

Following a structural survey, the building to be repaired is typically treated in three phases. Phase 1 is the repairs to any damaged concrete through surface repair, which usually entails the loose surface concrete being cut out and replaced. Phase 2 is the treatment of the embedded steel work within the structure, in the case of the VPI, this means, placing the material at close proximity to the steel within the concrete structure, by drilling holes and inserting the VPI material. Phase 3 is to seal the drilled holes and optionally resurface the repaired structure, where a cosmetic finish is required.

 

Step 1) To cleaned and repaired concrete areas, 25mm holes are drilled to a depth of 55mm in a grid pattern spaced 1m apart horizontally and 50cm staggered vertically. To beams and columns the spacing should be calculated from survey data but on no account should the spacing be greater than 1m apart in the centre of the sections.

 

 

Step 2) To the dust free hole a 1cl (10g) cartridge of VPI 580 is placed.

 

 

Step 3) Following insertion of the cartridge, a wadding pad is placed and the hole is infilled with a concrete repair mortar used in general repairs.

 

 

Step 4) The blend of all 3 inhibitors in the 580 product tackles the problem of steel reinforcement corrosion in concrete by migrating through the concrete and coating the steel with a mono-molecular coating locking out corrosive forces and stabilising the structure.