COATINGS FOR STEEL & CONCRETE Purpose : Concrete to be protected for chloride attack in aggressive...
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Transcript of COATINGS FOR STEEL & CONCRETE Purpose : Concrete to be protected for chloride attack in aggressive...
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COATINGS FOR STEEL & CONCRETE Purpose : Concrete to be
protected for chloride attack in aggressive environment (marine/Industrial area)
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STEEL SELECTION & COATINGS Corrosion resistant steel
reinforcement Bass (CRS bars) Method developed by CECRI
(Central Electro Chemical Research Institute Karaikudi, TN)
Inhibited cement slurry coating system
Cement polymer composite coating system
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Fusion bonded epoxy coated rebar (FBECR)
Hot dip galvanizing Epoxy - phenolic Interpenetrating
polymer network (IPN) coating Truncated inhibited slurry cement
base coating (used in KRCL)
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CORROSION RESISTANT STEEL SAIL – HCR bass TISCO – TISCON – CRS - TISCON – TMT They have dual micro structure
with inter surface tempered& at outer surface Ni, Chromium,
Copper & Phosphorous also added.
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CEMENT SLURRY COATING Derusting – Dipping in acidic,
alkaline, water Phosphating – phosphate jelly for
temp protection between de-rusting and cement slurry coating
Cement slurry – 2 coats of OPC cement slurry & inhibitor solution
Cost 2000-3000/MT
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CEMENT – POLYMER COMPOSITE COATING SYSTEM (CPCC)
Surface preparation – sand blasting Coating – one coat of Rapid setting
primer (dipping or brush) After 30 minutes – cement polymer
sealing coat Dried for 6 hours Cost 3200-8000/MT
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FUSION BONDED EPOXY COATING (FBEC) Degreasing & Cleaning by shot blasting
or grit blasting Heating – Approx temp 2300
Coating – Bar fed in coating bath where epoxy powder sprayed electrostatically. Epoxy powder melts, flows, gels, cures, cools and produces uniform coating
Forced cooling by water spray Cost 4500-13000/MT
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HOT DIP GALVANISING Galvanising is the process of deposition
of zinc over surface of rebars Removal of oil, grease etc by dipping into
caustic solution & rising Scale rust removed by pickling in
H2SO4/HCL & rising with clean water OR Sand blasting done alternatively Immerse bars in molten zinc (98.5%
pure) at specified temp of 450C Rebars dried Successful where carbonation risk is
there but not suitable for chloride attach.
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TURNCATED INHIBITED CEMENT
SLURRY COATING FOR DRY CLIMATE Partial CECRI system Cost = 500/per MT Clean by wire brush etc One coat cement slurry (1 kg cement +
600 cc of inhibitor solution) by dipping or brushing
Dry for 24 hrs in shade 2nd similar coat and dry for 24 hrs in
shade
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RECOMMENDED COATING FOR CONCRETE
Aggressive environment (Sieve, VS, Exten)
Non aggressive environment
Important structure
Other structure (Mild/Moderate)
Cement – polymer composite crating(CPCC) OR
CPCC OR Turncated inhibited cement slurry coating
Fusion bonded Epoxy crating
Inhibited cement slurry coating
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EPOXY PHENOLIC IPN (INTERPENETRATING POLYMER NETWORK) (Developed by CBRI Roorkee)
Sand blasting 1st coat of IPN by brush/spray 2nd coat with 4-8 hem Cured for 48 hrs Epoxy phenolic ipn
Part A – Resin component Part B – hardener component Added 1:1 by volume & vigorous stirred for
5-10 minutes
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COATINGS FOR CONCRETE Epoxy phenolic IPN Crating Integrated 4 – coat system – CECRI Epoxy coating Coal tar coating
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EPOXY IPN COATING Preparation of IPN polymers Two different resins
A medium viscosity epoxy resin An aromatic armine Cross linked & phonotic resin
obtained
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INTEGRATED FOUR COAT SYSTEM Epoxy polyamide Iron oxide – 1st
coat Epoxy polyamide MiO – 2nd coat
(porous) Epoxy polyamide TiO2 – 3rd coat Epoxy polyamide aliphatic – 4th coat
(tough polymer) Cost – 320/M2
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EPOXY COATING Thickness of coating – 8 to 15 Curing by amines or polyamides They are classified as under
Solvent base epoxy Thin thixotropic liquid epoxy based
primer Thick epoxy coating applied by spray.
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COAL TAR FOR EPOXY They have properties of both
coaltar & epoxy Good adhesion with concrete &
chemical resistant Two coats (total thickness 150 –
200 u) applied by rollers or airless spray.
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SELECTION OF CONCRETE COATING
Aggressive Non aggressive
Sub structure – coal tar epoxy
Not required
Super structure – Epoxy phenolic IPN or CECRI four coat
Blended cement can be used Dense concrete with sufficient cover enoughClean R/f bar be used.