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Galvanised reinforcement will provide some improved corrosion resistance in situations in which carbonation is the main problem. It does not provide any significant protection against chloride attack.
Standard reinforcing bars are hot dip galvanized, in accordance with BS EN ISO 1461. Either straight bars may be cut and bent to the required shape or complete fabricated cages may be dipped. However, the latter may lead to variations in the coating thickness.
It should be noted that the cost of galvanised reinforcement will be about twice that of carbon steel. However, it may be a viable alternative in aggressive locations with the higher initial cost being justified by reduced maintenance or an extended service life. The normal requirements for concrete quality and cover should not be relaxed.
No significant modifications to the usual design methods are required. Galvanized reinforcement will cause the formation of hydrogen in the fresh concrete. To prevent this, the bars should be passivated in a dichromate solution prior to casting, or a suitable concrete admixture should be used.
If galvanised reinforcement is mixed with plain carbon steel reinforcement in the same concrete element, then they need to be completely isolated electrically, otherwise accelerated depletion of the galvanising can occur.
For further information see Concrete Advice No. 07, Galvanised steel reinforcement.
Acknowledgement: The Concrete Society
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