Galvanized reinforcement

Galvanized reinforcement offers significant advantages compared to carbon steel under equivalent circumstances. These include an increase of initiation time of corrosion a greater tolerance for low cover, e. g. in slender (architectural) elements, and corrosion protection is offered to the reinforcement prior to it being embedded in concrete. 

M. T. Bianco, C. Andrade, A. Macias, SEM study of the corrosion products of galvanized reinforcements immersed in solutions in the... 

E. Maahn, B. Seirensen, The influence of microstructure on the corrosion properties of hot-dip galvanized reinforcement in concrete , Corrosion, 1986, 42, 187-196. 

All of the correlations seen above refer to situations of steel reinforcement in the free corrosion condition, that is, in the absence of factors that modify the potential of the system. They are in particular not appHcable to structures in concrete containing corrosion inhibitors galvanized reinforcement (on stainless steel it is possible in the same way) structures subjected to electrical fields produced by stray current that induce current exchange between reinforcement and concrete (this case is dealt with in Section 9.4). 

M. Unz, Performance of galvanized reinforcement on calcium hydroxide solution, Proc. ACI J. 

L. Maldonado, Chloride threshold for corrosion of galvanized reinforcement in concrete exposed in the Mexican Caribbean, Mater. Corros. 60 (2009) 536—539. 

F. Tittarelh, G. Moriconi, Comparison between surfece and bulk hydrophobic treatment against corrosion of galvanized reinforcing steel in concrete, Cem. Concr. Res. 41 (2011) 609-614. 

It may be very risky to apply electrochemical treatments to galvanized reinforcing steel. Very severe pitting can result. NCT, the patent holders on the realkalization and desalination techniques, do not recommend their use on structures containing galvanized rebar (Miller, 1995). 

Hot dip galvanized reinforcing bars or mesh are valuable in precast faqade units to ensure that rust will not discolor the facade. 

ILZRO(1988). Galfan Manual, 3rded. ILZRO, Research Triangle Park, NC, 139 pp. ILZRO (1981). Galvanized Reinforcement for Concrete—II. ILZRO, Research Triangle Park, NC, 208 pp. and appendices (includes bibliography of 394 refs). 

Martin, H., and Rauen, A. (1975). Studies on the Behavior of Galvanized Reinforcing Steel in Concrete. Gemeinschaftsausschuss Verzinken eV, Diisseldorf, Report 68, pp. 61-77 (in German). 

Otto, M. J. (1976). Einstatz feuerverzinkten Bewehningsstahls bei der Olgewinnung in der Nordsee (Introduction of hot dip galvanized reinforcing steel for oil extraction in the North Sea). Verzinken 5(1), 5-7 (in German). 

Porter, F. C. (1985). Galvanized reinforcement for concrete. 1st Int. Conf. Deterioration and Repair of Reinforced Concrete in the Arabian Gulf. Construction Industry Research and Information Association (U.K.), pp. 193-201. 

Clear, K. C., "Time-to-Corrosion of Reinforced Steel in Concrete Slabs, Vol. 4—Galvanized Reinforcing Steel, Interim Report, December 1981, Federal Highway Administration Report No. FHWA/RD-82/028, FHA, U.S. Department of Transportation, Washington, DC. 

The fibre surface has a considerable influence on the composition of the transition zone. For highly corrosion resistant glass fibres with specially coated surface, like CemFILl, this zone is very porous. This is in contrast to the strong interface formed around steel and asbestos fibres. In various composites with different kinds of fibres and matrices, the transition zone is formed as a result of chemical affinity, quality of the fibre surface and the penetration of the cement paste into the bundles of fibres. Furthermore, the ITZ may be different above and below a fibre due to bleeding and water lenses below fibres. Higher porosity of the ITZ around steel galvanized reinforcements than around ordinary steel rebars was observed by Belaid et al. (2001). 

Galvanized reinforcement, i.e. zinc coatings formed by dipping clean rebars in a bath of molten zinc, can protect steel in concrete from corrosion attack. However, the performance reported in the literature is contradictory (Bentur et al., 1997). Galvanized rebars remain passive in carbonated concrete and the corrosion rate is much lower than with black steel. In situations where chloride induced corrosion prevails, a delay in the initiation of corrosion can be expected, but at high chloride concentrations depassivation cannot be avoided completely. 

Despite the above considerations, the performance of galvanized reinforcing steel has had somewhat mixed reviews. One explanation provided for low performance levels has been the formation of a particularly voluminous corrosion product involving expansions greater than those of many iron corrosion products. 

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