The use of adhesively bonded UHM carbon fibre plates to strengthen cast iron structure has been established for many years. Essentially it appears a very similar installation to bonding plates to concrete structures. However, the loads carried by the strengthening mean the bond line interfaces work much closer to the limits of the adhesive properties when strengthening cast iron.
There are examples where the selection of installers with experience in application of strengthening systems to concrete have had problems installing plates on cast iron structures. These have usually been caused by operatives following widely acceptable procedures on concrete and using them on cast iron, and adhesion issues have been exposed due to the higher performance required from the bond lines.
Adhesives for use in bonding UHM CFRP plates to cast iron should be considered carefully. Selection of adhesives that may be suitable for application to concrete, can also lead to problems when used on cast iron.
Designers and clients need to take responsibility to select and insist on the correct materials and installer being used to avoid issues.
Clients who have gone through the learning curve on these issues, will make sure that designers and installers all have a proven track record for installing systems. This track record needs to present at both management and operative level, to ensure correct installation procedures are followed at all times.
A classification system for the acceptable performance of adhesives for use in bonding UHM CFRP plates to cast iron was established by Oxford Brookes University as part of a DTI funded project called CompClass. All the established and experienced designers, material suppliers and contractors had an input into this project.
The minimum any adhesive system should have is the following classification certificate showing that it is suitable for the use of bonding CFRP onto cast iron. If there is a significant interval between preparation and application, then this system needs to include a primer suitable for cast iron. In this situation the performance of the primer, not only as a corrosion protection system, but also its ability to transfer loads, then becomes the critical. An example of material classification certificate can be seen in the link below.
Failure to use experienced installers, designers and adhesive systems with the correct performance can potentially premature system failure.