1. Although the construction code specifies galvanized rebar, the use of galvanized rebar is not common practice in most jurisdictions.

Galvanizing provides protection to steel from corrosion and it may be that it was specified in Bermuda because reinforced concrete structures historically suffered from corrosion.

However, what we have found in the construction is that the vulnerability of reinforcement rod in concrete is affected by a number of factors.

These include the density of the concrete or conversely the porosity, the presence of chloride ions (salts) due to migration of salts into the concrete facilitated by high porosity and cracking of concrete. 

2. Notwithstanding, there are a number of ways to protect against corrosion: galvanizing and the use of stainless steel or epoxy coated reinforcement are direct methods of protecting the steel itself.

Stainless steel is more commonly used in the UK than galvanizing or epoxy coating because they both require detailed inspection and repairs to any damage to the coating as well as being unsuitable for site changes due to likely damage to the coatings. The use of coatings can also adversely affect the bond of the concrete to the reinforcement with a consequent reduction in structural strength.  All three of these options carry a cost penalty and galvanized or epoxy coated reinforcement carry a time penalty in repairs that cannot be avoided.

3. The more common practice is preventative action, which is to say that the density of the concrete should be kept high and cracking should be controlled.  High density concrete is achieved by specifying a high strength concrete and by preventing bad site practices such as adding water on site to make the concrete easier to place.

The practice of adding water leads to there being too much water for the cement to hydrate and the water that is not used then draws in salts and causes corrosion.  Also, the concrete must be adequately compacted, for this constant supervision is needed to ensure that the concrete is worked sufficiently for all of the air in the concrete to be removed.

Cracking is controlled through adequate reinforcement, this is often more steel reinforcement than is necessary structurally but it is added to control early thermal cracking which can be caused when the cement reacts exothermically during the curing process.

This can also be controlled through good site practices and maintaining a low temperature in the concrete during curing by cooling the surface with wetted burlap.

4. Additional protection can be added through modern additives such as corrosion inhibitors that increase the alkalinity of the concrete thus reducing the likelihood of corrosion and agents that reduce penetration of the concrete by moisture and remain active within the concrete to seal cracks as they occur through the early life of the structure.  These prevent the start of corrosion.

5. Another method of corrosion protection commonly used is cathodic protection.  This involves connecting all of the steel in the structure electrically and then either applying anodes as one would with a boat that will corrode sacrificially for the reinforcement or applying an impressed current to prevent corrosion.

The use of galvanized rebar is the simplest approach when applied across the board and when modern techniques to limit corrosion are not employed.

This is why quite reasonably it may be specified in the building code.  It can make up for deficiencies in construction quality control and will help protect against corrosion in a lower quality reinforced concrete element.  We were aware that the use of non-galvanized reinforcement is not in line with common local practice and therefore, we sought professional advice to clarify this matter before making a final decision. 

Advice of fully qualified corrosion specialists was that in the product that we are producing the use of galvanized reinforcement would have little or no benefit.

We balanced this against the increase in cost and also the delays to construction through both increased delivery times and repair requirements and we decided that the inclusion of galvanized reinforcement was not justified. The Department of Building Control were informed of this decision and the rationale behind it at the time and given the opportunity to comment, they accepted our approach.

At Heritage wharf a 50 MPa concrete is being used. This high strength, high-density mix will provide protection to the steel.

The reinforcement in the structures has been detailed to control early thermal cracking.  To enhance the properties of the concrete to protect against corrosion we have added both a corrosion inhibitor and an agent to reduce moisture penetration of the concrete mix. 

The specification has detailed requirements for placing and curing of the concrete such as compaction methods and temperature control as mentioned above.

This approach is we believe more effective than the use of galvanized reinforcement and it prevents the time delays to the project that we cannot afford. 

In addition we are providing electrical continuity between all of the steel elements so that a cathodic protection system can be fitted. 

This system will be fitted after completion of the works; it has not been designed for the improvement works in isolation because we are aware of corrosion problems with the existing structure and believe that it will be more cost effective to install a system to protect all of the dock.  The new elements of the dock will be well protected in the meantime through the measures outlined above and the high spec epoxy coating on the steel piles.

The Ministry will continue to keep the public abreast of the project as we count down to May 15th.