20.07.2014
Hot dipped galvanized rebar relies on a sacrificial zinc coating to protect the underling black steel rebar from rusting. 23-year-old Ontario bridge deck reinforced with Galvanized rebars suffering from corrosion induced cracking. All types of steel will eventually rust causing premature degradation of concrete structures. Researchers believe that this is due to the differences in the modulus of elasticity between GFRP and steel. The Long Term Performance of Three Ontario Bridges Constructed with Galvanized Reinforcement.
2007 Abstract: Corrosion of the galvanized reinforcement caused significant damage to the concrete, in the form of delaminating and cracking. The range of values of chloride content at corrosion initiation is greater for galvanized reinforcement than for conventional reinforcement.
Concrete adjacent to the non-chromate treated bars evaluated in this study revealed no evidence of an increase in porosity due to hydrogen gas evolution during curing when compared to conventional reinforcement in similar air-entrained concrete.
Abstract: This report also present reviews the failure of the masonry facade at a bank in Cleveland, OH, where cracking of the mortar and brick occurs over galvanized re-bar. Performance of galvanized reinforcing bars in reinforced masonry and concrete has had mixed reviews. The Chair’s researchers have conducted field tests on more than 10 bridges across Canada… FRP materials can be preserved for 100 years or more.
2008 Abstract: This study reviewed 5 Canadian bridges and 1 Canadian harbour that were constructed in the early 1990’s. As the price of stainless steel increases, fiberglass is filling the material gap because of its resistance to corrosion, its high strength, and its easy fabrication.  Also, more people are turning to fiberglass as a alternative grating because it has little secondary scrap value and is less likely than is cast iron to be stolen for recycling.


Pultruded bar grating has potential to replace cast iron grating of the same dimension, though not at the same price. Although it has occasionally been credited with extending the life of concrete structures, it often has had little or even a negative impact on concrete life. In certain applications, the by-products of the reaction will cause coating expansion rates of up to 260%. This eliminates problems related to zinc coating de-bonding experienced particularly on galvanized bends. In the most severely damaged of the three structures, 10% of the surface area was delaminated, or had already been repaired, within 20 years of construction.Galvanized reinforcing bars are not recommended as the primary or sole means of corrosion protection for structures exposed in the Ontario highway environment. On the low side, galvanized steel exhibited values that are similar in magnitude to those exhibited by conventional steel.
The galvanized bars, however, showed signs of corrosion, including exposure of the inter-metallic layer on some.
Department of Transportation Federal Highway Administration”(FHWA) memorandum quoted in (6) suggests a 15-year life for galvanized re-bar in good quality concrete.  The 15 year FHWA conclusions were supported by Andrade et.
Substantially higher longevity has been found over regular mild steel rebar in some situations (1-3) but only slightly better (4), equal or worse performance (5-8) have been found in other exposures.
However, its corrosion rate was less than the corrosion rate of both galvanized A  and galvanized B.  The reason may have been due to the fact that galvanized B was coated after it was bent, while galvanized A was bent after it was coated.
By contrast, steel-reinforced concrete will begin to deteriorate after 10 to 15 years and will generally require major repairs after 25 years. While the grate is strong on its own merits, and the cross members help to concentrate that strength, if a vehicle’s wheels turn too abruptly while on the grating the cross members can be weakened and compromise the grate’s overall strength This can be an issue in some high traffic applications. It also eliminates premature degradation due to surface defects experienced with galvanized re-bar.


Based on the findings of this study, they do not provide effective long-term protection from corrosion. The loss of the zinc layer may be due to the lack of chromate treatment or due to loss of metal in the presence of high-pH concrete pore solution; increased porosity relative to the concrete above the bar.
Several investigators have reported such discrepancies and have suggested factors that might be involved.
A NACA duct will transfer air into or out of a vehicle with minimal drag increase.These ducts are easily attached with bonding compound or riveted to fiberglass, aluminum, and steel body panels.
The corrosion product occupied 260% more space than Zn and produced a much greater expansive. The longevity conclusions from the studies contributed to the adoption of GFRP as an approved reinforcement for Canadian and American Civil Structures. As metal corrodes it expands.  In concrete this causes degradation resulting in loose bonding, spalling, cracking and breakage. Clear (8) reported that galvanized rebar, when used in both mats in a bridge deck, will outperform black steel by only two years.  McCrumb and Arnold (9) conclude that galvanized reinforcement will add five years to the service life of a bridge compared to black reinforcement.
However, most investigators failed to report all data needed to determine correlations between these factors. The present work reviewed the failure of the masonry facade at a bank in Cleveland, OH, where cracking of the mortar and brick occurred over galvanized re-bar.



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