EPOXY-COATED REBARS IN EPOXY-COATED REBARS IN CONRETE CONSTRUCTIONCONRETE CONSTRUCTION

Ahmad S. Al-GahtaniAhmad S. Al-Gahtani

Department of Civil EngineeringDepartment of Civil Engineering

King Fahd University of Petroleum & King Fahd University of Petroleum & MineralsMinerals

Epoxy coating procedure

Deterioration of bridge decks in the 1960”sResearch by U.S FHWAFirst bridge in 1973 in Philadelphia

By 1977, 17 states adopted the use of FBECR

Early studies showed FBECR is effective in reducing corrosion by many folds (11-41 times) compared to black steel(FHWA 1977-81)

Background :

Florida Experience:

Florida long key bridges constructed in 1979

In 1986 substructures showed signs of corrosions in major five bridges

Corrosion was in tidal/splash zone (0.6-2.4 m above water mark)

Florida Investigation:

Disbondment of coating Water blisters under the coating Corrosion initiated at damages/imperfections Corrosion aggravated by:

- Fabrication bending- Exposure to salt air in construction yard

- Coating defects/damages In 1992 Florida D.O.T. discontinued

use of FBECR.

Performance of ECR in Performance of ECR in Pennsylvania (I)Pennsylvania (I)

11 bridges with ECR (ages 6 to 10 11 bridges with ECR (ages 6 to 10 years) and 11 bridges (comparable years) and 11 bridges (comparable ages) with plain rebar subjected to ages) with plain rebar subjected to deicing salt service. Initial stages of deicing salt service. Initial stages of corrosion observed in the plain bar corrosion observed in the plain bar bridges but not in the ECR structures. bridges but not in the ECR structures. Chloride ~ 0.7 Kg/m Chloride ~ 0.7 Kg/m33.. 1987 1987

Performance of ECR in Performance of ECR in Pennsylvania (II)Pennsylvania (II)

Investigation of epoxy coated rebar Investigation of epoxy coated rebar and other protection systems of 21 and other protection systems of 21 bridge decks ( ages 10 years) in bridge decks ( ages 10 years) in deicing salt , Chloride ~ 7 kg/mdeicing salt , Chloride ~ 7 kg/m33 Both ECR rebar provided the most Both ECR rebar provided the most effective protection performance, effective protection performance, some rebars being in excellent some rebars being in excellent condition despite high chloride condition despite high chloride contents .contents .

Performance of ECR in Canada Performance of ECR in Canada (C-SHRP)(C-SHRP)

19 ECR structures (3 to 16 years old) 19 ECR structures (3 to 16 years old) The ECR bars showed varying degrees of The ECR bars showed varying degrees of corrosion damage, with concrete damage corrosion damage, with concrete damage and/or significant corrosion on bars at and/or significant corrosion on bars at cracks and in low cover areas with high cracks and in low cover areas with high chloride. Many uncorroded after up to chloride. Many uncorroded after up to 16 years service when no significant 16 years service when no significant chloride had reached the bars. About chloride had reached the bars. About 50% of bars showed reduced coating 50% of bars showed reduced coating adhesion,adhesion, (1992). (1992).

Performance of ECR in Canada Performance of ECR in Canada (Ontario)(Ontario)

Ontario MOT, during 1989-1995, Ontario MOT, during 1989-1995, evaluated ECR in numerous structures in evaluated ECR in numerous structures in deicing salt service. Initially found little deicing salt service. Initially found little deterioration of ECR except for damage deterioration of ECR except for damage in a barrier wall in a barrier wall 10 years old. By 1992 10 years old. By 1992 multiple instances of ECR corrosion were multiple instances of ECR corrosion were observed. Coating disbondment was observed. Coating disbondment was observed. ECR was viewed as providing observed. ECR was viewed as providing an improvement over plain steel, but the an improvement over plain steel, but the suitability for 75-year durability was suitability for 75-year durability was questioned [16].questioned [16].

Performance of ECR in New York Performance of ECR in New York Bridge Decks (1992)Bridge Decks (1992)

DOT examined 14 of 7-12 year old "worst-DOT examined 14 of 7-12 year old "worst-case" bridges with deck surface distress ed in case" bridges with deck surface distress ed in deicing salt service. Rebars from cores, 65% deicing salt service. Rebars from cores, 65% had negligible corrosion, 30% had corrosion had negligible corrosion, 30% had corrosion at ribs only and 5% showed more pronounced at ribs only and 5% showed more pronounced corrosion. No undercoating was observed corrosion. No undercoating was observed surrounding corroded areas. Chloride surrounding corroded areas. Chloride 2 2 Kg/mKg/m33; the incidence of corrosion was not ; the incidence of corrosion was not observed to be correlated with chloride level. observed to be correlated with chloride level. Long-term corrosion performance could not Long-term corrosion performance could not be quantified yet.be quantified yet.

Performance of epoxy coated in Performance of epoxy coated in Virginia (1993)Virginia (1993)

Transportation Research Council Transportation Research Council investigated the condition of ECR in two investigated the condition of ECR in two test bridges built in 1977 and in deicing test bridges built in 1977 and in deicing salt service for 13 years. Chloride salt service for 13 years. Chloride 2 2 Kg/mKg/m33) . ECR bars were of early types, ) . ECR bars were of early types, with many flaws and holidays. However, with many flaws and holidays. However, coating disbondment or signs of severe coating disbondment or signs of severe rusting were not observed. It was rusting were not observed. It was concluded that the combination of concluded that the combination of adequate depth of cover and ECR adequate depth of cover and ECR provided excellent protection.provided excellent protection.

Performance of ECR in a Coastal Performance of ECR in a Coastal Georgia Bridge (1993)Georgia Bridge (1993)

Georgia DOT examined ECR in the Georgia DOT examined ECR in the substructure of a 9-year old marine bridge substructure of a 9-year old marine bridge (seawater tidal and splash service). Coating (seawater tidal and splash service). Coating disbondment was observed at several of the disbondment was observed at several of the ECR samples extracted. Severe corrosion of ECR samples extracted. Severe corrosion of ECR was observed at an area of poor ECR was observed at an area of poor concrete consolidation. It was concluded that concrete consolidation. It was concluded that ECR provided questionable added corrosion ECR provided questionable added corrosion protection, and recommended that epoxy protection, and recommended that epoxy coating not be used in continually wet marine coating not be used in continually wet marine substructure.substructure.

Performance of ECR in West Performance of ECR in West Virginia Bridges (1994)Virginia Bridges (1994)

DOT investigated 14 bridge decks DOT investigated 14 bridge decks ((13 years old) in deicing salt service 13 years old) in deicing salt service using ECR and plain bar. ECR using ECR and plain bar. ECR bridges exhibited little or no distress bridges exhibited little or no distress while plain bar bridges showed 2-17% while plain bar bridges showed 2-17% deck delamination. Chloride deck delamination. Chloride 1.5 to 1.5 to 3 Kg/m3 Kg/m33. It was concluded that use of . It was concluded that use of ECR resulted in dramatic reduction of ECR resulted in dramatic reduction of delamination in bridge decks.delamination in bridge decks.

Performance of ECR in Coastal Performance of ECR in Coastal North Carolina Bridges (1993-North Carolina Bridges (1993-1995)1995)

DOT examined the ECR in the DOT examined the ECR in the substructure of three marine bridges substructure of three marine bridges (splash-tidal seawater service), (splash-tidal seawater service), 8 8 years old. Chloride ~ 1-2 Kg/myears old. Chloride ~ 1-2 Kg/m.. No No significant corrosion of ECR or coating significant corrosion of ECR or coating disbondment was observed. It was disbondment was observed. It was concluded that epoxy coating in the concluded that epoxy coating in the selected bridges was providing selected bridges was providing adequate corrosion protection at time of adequate corrosion protection at time of the survey.the survey.

Performance of ECR in California Performance of ECR in California (1995)(1995)

4 bridges, 7 to 10 years old in deicing 4 bridges, 7 to 10 years old in deicing salt service. Preliminary findings salt service. Preliminary findings revealed ECR corrosion in 8 of 32 cores revealed ECR corrosion in 8 of 32 cores examined; chloride examined; chloride 10 Kg/m10 Kg/m33. Some . Some bars were showing no corrosion with 6 bars were showing no corrosion with 6 Kg/mKg/m33 chloride. Coating disbondment chloride. Coating disbondment was observed at some of the bars. The was observed at some of the bars. The concrete was often dry for extended time concrete was often dry for extended time periods. The bridges examined were not periods. The bridges examined were not showing severe distress.showing severe distress.

Performance of ECR in Indiana Performance of ECR in Indiana (1995)(1995)

Investigations by Purdue University Investigations by Purdue University of 5 bridges in deicing salt service. of 5 bridges in deicing salt service. Preliminary findings showed no Preliminary findings showed no corrosion or disbondment ,Chloride corrosion or disbondment ,Chloride 2.5 Kgm2.5 Kgm33 . Corrosion of ECR was . Corrosion of ECR was seen at one bridge at bends in the seen at one bridge at bends in the bar and chloride bar and chloride 3 Kg/m3 Kg/m33..

Performance of ECR in Kansas Performance of ECR in Kansas (1995)(1995)

DOT investigated Bridges in deicing DOT investigated Bridges in deicing salt service made in 1995 [24] . salt service made in 1995 [24] . Preliminary findings show chloride Preliminary findings show chloride levels at rebar depth less than 0.5 levels at rebar depth less than 0.5 Kg/Kg/33 and good ECR condition. and good ECR condition.

Performance of ECR in Performance of ECR in Minnesota (1995)Minnesota (1995)

DOT in 1994 investigated 10 bridges DOT in 1994 investigated 10 bridges in deicing salt service. Cores taken in deicing salt service. Cores taken from cracked concrete showed only from cracked concrete showed only one core with ECR corrosion. one core with ECR corrosion. Satisfaction with ECR performance Satisfaction with ECR performance was reported, indicating that bridge was reported, indicating that bridge overlays and good concreting were overlays and good concreting were also factors in the observed also factors in the observed performance.performance.

Code Amendments;

Upgrade in specification,-Min. thickness 130 175 - Number of holidays 6/m 3/m

- Damages 2% 1%

- Improvement of adhesion, handling

and storage procedures

- Plant certification program

Sales in USA:Sales in USA:

100000

120000

140000

160000

180000

200000

Ton

nes

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

Time (year)

Use of FBECR in the Gulf:

Early 1980s used in some projects in U.A.E.

By mid 1980s set up of coating plants in U.A.E. (now 5 plants)

Early 1990s 3 plants established in Eastern Province of S.A.

1996/97 New plant in State of Qatar.

Total: 9 plants

0

10000

20000

30000

40000

50000

60000

70000

80000

90000

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

Ton

es

Time (Year)

Sales in Saudi Arabia:

Research Experience:Research Experience:

CE-KFUPMCE-KFUPM• SpecimensSpecimens prisms 120 X 120 X 305 mm prisms 120 X 120 X 305 mm

four bars with 25mm coverfour bars with 25mm cover

• ReinforcementsReinforcements Mild steel, galvanized steel, Mild steel, galvanized steel, FBECR and stainless steelFBECR and stainless steel

• ContaminationContamination 2.4, 4.8 and 19.2 kg/m2.4, 4.8 and 19.2 kg/m33 of of chloridechloride

• ExposureExposure Natural exposure site, Natural exposure site, Dhahran (above ground)Dhahran (above ground)

Specimens at eSpecimens at expxposure osure site:site:

onset and propagation of cracks

weight loss in rebar

bar condition (rust and pitting)

Performance Criteria:Performance Criteria:

Results (after 7 years exposure):

13 16

71

1320

50

17

42 42

16

100

0

20

40

60

80

100

120

1 2 3 4 5 6

Black Steel FBECR

2.4 kg/ m3 4,80 kg/ m3 19,2 kg/ m3

Crack category1 - No crack 4 - Wide2 - Fine 5 - Heavy3 - Medium 6 - Spalling

Retrieved Retrieved bars:bars:

Specimens : prisms 62.5 X 100 X 305 mm

62.5 X 202 X 305 mm

with 25 mm cover

Reinforcements: FBECR straight bars

& J-bend bars

Exposure: 5% sodium chloride solution,

in room temp.

(Accelerated lab. testing)

RI-KFUPM Study:

Results:

Coating disbondment

Corrosion at coating cracks

Corrosion started at deformation patterns

Corrosion proceeded underneath coating

Corrosion underneath coating

U.A.E. Study:

Dubai Municipality, 1991

Specimens: 150 X 150 X 360 mm with 10 mm and 30 mm cover

Reinforcements: FBECR and black steel

Exposure: -Below ground

-Tidal zone

-Above ground

Results after 3 years:

FBECR generally in good conditions

Some adhesion loss of coating for below and tidal specimens

Specimens collected from construction sites were far from satisfactory w.r.t. ASTM standards

Local Construction Practices:

Improper Cut and Bend at job sites

Improper storage at sites

No repair for damages

Mix of coated and uncoated rebars

Unskilled laborers (damages, scratches

bending, cutting, )

Cut and Bend at job sites

Storage at sites

Coating damages

Mix of rebars

Ineffective patching

Sharp edge and seem in Sharp edge and seem in rebar:rebar:

Gulf Environment Conditions:

Favorable Corrosion Conditions:- High temp. with salt laden humidity

- High level of contamination of

construction materials

Temp.

Cl-R.H.%

CONCLUDING REMARKS

Good quality FBECR would provide satisfactory protection if constructed with good quality concrete.

Moisture and temperature of the exposure conditions are key factors for the disbondment of coating.

Epoxy-coating powders shall be handled without exposure to high temperature (above 30°C).

CONCLUDING REMARKS

Long storage time for reinforcement and time between cleaning and coating should be minimized.

Storage time at the construction site should be limited.

Repair of damaged coating by touch-up should be done immediately.

Plant fabrication is highly preferable.

CONCLUDING REMARKS

Bending at site should be carried by proper

equipment and tools.

Mix of uncoated and coated reinforcement should be

avoided.

Construction interruption should be minimized.

Manufacturers of rebars should produce more

suitable product for coating.

THANKSTHANKS

Initiation-Propagation Model:

Loss of adhesion

Salt ingress

Initiation Propagation

TimeSalt ingress

Loss of adhesion

Salt ingress

Black Steel

FBECRIn Poor Conc.

FBECRIn good

Conc.