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International Zinc Association
Production Technology and Performance of Corrosion-Resistant
Zinc-Coated Rebar
Frank E. Goodwin Sc.D.International Zinc Association
Durham, NC USA
International Zinc Association
Production of Rebar by General Galvanizing
International Zinc Association
General Galvanized Coating
3
125 μm Coating(915 g/m2)
______
______
International Zinc Association
General Galvanized Rebar Products
Straight bars
Mesh
Stirrups and ties
International Zinc Association
Effect of galvanizing on grades of reinforcing steel
International Zinc Association
Effect of General Galvanizing on Mechanical Properties of Carbon Steels
Degrease 3 minutes, Pickle 18.6% HCl 50 minutes, Flux 25 minutes, Zn dipping 2.5 minutes
International Zinc Association
Surface preparation
Induction Heater
Zinc / zinc alloy trough Black, uncoated
rebar from mill
Air knife
Pre-heat
Galvanizing
Shot Blasting
Spray-On Flux
In-Line Rebar Galvanizing Process
Galvanized rebar
International Zinc Association
In-Line Galvanized Coating
60 μm Coating
Zinc Layer
SmallFe2Al5-xZnx
Layer
International Zinc Association
CGR Galvanizing Section at Supergalvanising, Dubai
International Zinc Association
Some details of the In-Line Process
• Blasting with S330-S280 steel shot
• Rinse in water to remove dust
• Optional short pickling in 11% HCl
• Flux in Ferrotech G-Flux-R at a target SG of 1.7-1.8
• Dry using high frequency induction heating to heat only a thin outer part of the rebar (200 KW per rebar is typical)
• Galvanizing in flooded tube for 1.8m, pumped from 35T kettle (for 8 rebars capability) 0.2%Al in Zn bath
• Control coating with gas wiping ring
• Line speed maximum 22 m/min
International Zinc Association
Excellent ductility of in-line coating
International Zinc Association
Excellent bending, galvanized and galvanized + epoxy
International Zinc Association
Bond Strength in Concrete
International Zinc Association
Results of 88h of Salt Spray Testing
International Zinc Association
Xiamen Newsteel Metal Products Co., LtdSalt Spray Test
Epoxy resin coatedsteel rebar
Zinc alloy coatedsteel rebar
Zinc+epoxy compositecoated rebar
Quantity 3 3 3
Dimensions, mm
14mm D x 25 cm L 14mm D x 25 cm L14mm D x 25 cm L
Surface finish
Make three man-made 3 mm diameter defects holes on each side ofthe rebar, the hole should penetrate the coating and reach to the steelbase, the holes located between ribs.
Neutral Salt spray test
Test solution:Concentration 5% Nacl solutionPH=6.8Test temperature: 35±Sample placement: Sample tilted 20 degrees from vertical, defect holestowards the cabinet side, after 24 hours continuous spray check samplesurface respectively.
Test result
1. After 24h, epoxy resin coated steel rebar corroded seriously (redrust) at defect hole area, epoxy coating loss of adhesion to rebar2. After 24h, zinc alloy coated rebar shows white rust corrosion but nored rust (steel attack).3. After 24h, zinc+epoxy composite coating show slight red rust inhole, no loss of adhesion of epoxy.
International Zinc Association
International Zinc Association
Final Report on 100-Year Bridge Research Program
Florida Atlantic University
About 11 years of exposure
International Zinc Association
Coated Concrete
Block
Upper Level
Reinforcement
Bottom
Reinforcement
(2)
Electrical Circuitry
for Potential and
Macro-Cell Current
Measurements
Salt Water
Bath
Exposed
Concrete
within Bath
ASTM G-109 Sample
International Zinc Association
Potential evolution of GV and BB bars with FA41 concrete, using standard sample
Potential evolution of GV and BB bars with CT41 concrete, using bent bars
International Zinc Association
Rebar Corrosion Model
International Zinc Association
Zn (eta) phase current density = 2.38 A/cm2 ( ______ line)Zeta (Zn-Fe) phase current density = 3.98 A/cm2 ( _ _ _ line)Therefore Zn 1.7 times more corrosion resistant than Zn-Fe in the concrete corrosion cell
pH=13NaOH
How does the 50 μm In-Line coating corrosion resistance compare to the 125μm General Galvanized coating? Results of potentiodynamic polarization tests
International Zinc Association
In the 125 μm general galvanized coating, the Zn layer is 52 μm and the ZnFe layers are 73 μm. The ZnFe
layers contribute the same as an additional 42 μm of Zn layer protection (Total is same as 92 μm Zn)
125 μm coating
International Zinc Association
Sydney Opera House, Sydney, Australia
• Work started in 1958, with 10,000 builders employed, and
opened in 1973
• Commissioned by the Queen of England 3,000 events annually
• Precast concrete shells reinforced with galvanized wire mesh.
Shells corrosion free for 42 years
• Foundation has been refurbished twice due to uncoated rebar
use
International Zinc Association
Lincoln Road Parking Garage, Miami, Florida
• Designed by Swiss firm Herzog & de Meuron, which also
designed Beijing's famed "Bird's Nest" Olympic Stadium
• 7 Story structure built with galvanized concrete
reinforcement in the slabs, columns, and ramps
• Juvia is a 10,000 sq/ft Asian restaurant and lounge on the
penthouse level
International Zinc Association
Brazil Museum of Art, Rio De Janeiro, Brazil
• “MAR” opened in 2013
• “MAR” design combined two adjacent structures Dom Joao
Palace and Police station into one new use structure
• 320 cubic meters of concrete and 70 tons of galvanized rebar
were used to construct the adjoining roof
International Zinc Association
Lotus Temple, New Delhi, India
• Design inspired by the lotus flower, and the structure is
surrounded by 9 ponds and completed in 1986
• The façade is marble
• The reinforcements used in the white concrete shells and the
binding wires were entirely galvanized to prevent the long-term
rusting of the reinforcement and staining the white concrete
International Zinc Association
Longbird Bridge, Bermuda
• Built by the US Navy and completed in 1953
• Extreme harsh environment (warm sea water)
• Deck is reinforced with galvanized rebar
• Rebar was inspected in 1984 with 98% of the galvanized
rebar in perfect condition
• Now 62 years old with no rebar maintenance necessary
International Zinc Association
Route 66 Bridge, Kittanning, Pennsylvania
• Built in 1973
• Concrete deck reinforced with galvanized rebar
• Median barrier wall upgraded in 2003 for safety reasons and
rebar was inspected
• Galvanized rebar in near perfect condition after 30 years
• Now 42 years old with no rebar maintenance necessary
International Zinc Association
Cape Town Sea Wall, Cape Town, South Africa
• 85 year old sea wall and popular tourist attraction
• “AKA” Sea Point promenade
• Side by side section (Built in 1990) below shows standard
rebar vs. Galvanized rebar performance
International Zinc Association
Shenzhen Metro Line No. 11, Shenzhen, China
• Currently under construction
• Opening later this year
• Fastest Metro line in Shenzhen with speeds of 120 km/h
• Galvanized rebar is being produced by Xiamen Newsteel
International Zinc Association
G7 Beijing–Ürümqi Expressway
Connects the cities of Beijing, China, and Ürümqi, Xinjiang. When complete, it will be 2,540 km (1,580 mi) in length.Galvanized rebar is being produced by Xiamen New Steel
International Zinc Association
Conclusions
• Both General Galvanized and In-Line Galvanized rebar will greatly extend the service life of reinforced concrete
• The production technologies for both products are settled
• The bond strengths of uncoated and galvanized rebar are equivalent
• New construction products will benefit greatly from Zn-protected rebar