pack rust identification and mitigation strategies for
TRANSCRIPT
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Pack Rust Identification and Mitigation Strategies for Steel Bridges
Mark D. Bowman, Prof. of Civil Engineering, Purdue UniversityChintan Patel, HDR, Indianapolis, Bridge EIT
JTRP Research Study SPR-4121
September 25, 2020
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Study Advisory Committee
•Timothy Wells (PA)•Stephanie J. Wagner (BO)•Christopher Wheeler• Jose Ortiz•Michael Black•Nathaniel Pfeiffer
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3 Major Tasks
•Literature review.•Reviewing existing mitigation strategies and repair procedures for selected DOTs.
•Pack rust in Indiana Bridges.
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Task 1Literature Review
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Pack Rust or Crevice corrosion
•Localized attack on metal surface.•Crevice formed between two joining surfaces.
• Metal – Metal• Metal – Non-metal
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Initiation Process• Crevice corrosion initiation process
• Differential oxygen concentration needed• Aqueous solution(water), pathway for ions to flow• Process accelerated
• [Cl¯] present• pH acidic present
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Mechanism• Formation of differential oxygen concentration cell.
7Steel Specimen
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Mechanism
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• Inhibitors like chromium decreases the corrosion rate.• Severe corrosion takes place near the mouth of the
crevice.
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Bulk pH > 7Crevice pH < 7
Steel Specimen
H+
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•Crevice height •Ranging from 0.1 mm to 3 mm.•Large enough to allow entry of electrolyte (water)
•small enough to not allow electrolyte to flow out.
Attributes of crevice corrosion
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• Rust build-up eventually seals the crevice and the corrosion process stops. (U.R.Evans, researcher in corrosion science)
On contrary
• Sealing the crevice without neutralizing the activecorrosion product can cause acceleratedcorrosion.(Roads and Bridges, Sept,2003)
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Task 2
Mitigation strategies and repair procedures of selected DOTs
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Mitigation and repair strategies•Stripe coat•Caulking •Penetrating sealer•Backer rod
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Stripe coat
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Caulking
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Penetrating sealer• Has viscosity to penetrate into the crevice.• Ability to neutralize the corrosive environment inside the crevice.
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Backer rod and sealant
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Backer Rod
Sealant
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State Dept. of TransportationStripe coat (21 states) Caulking (10 states) Penetrating sealers
(5 states)Backer rod (2 states)
Alabama, California, Delaware, Florida, Georgia, Illinois, Indiana, Iowa, Maryland, Massachusetts, Minnesota, New Jersey, New York, North Carolina, North Dakota, Ohio, Oregon, South Dakota, Virginia, West Virginia, Wisconsin
California, Delaware, Florida, Iowa, Maryland, Missouri, Ohio, Oregon, Washington, West Virginia
Washington, Missouri, Iowa, Illinois, Delaware
Oregon, Washington
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Repair Procedure
Oregon• Remove pack rust by mechanical cleaning, and
heating water-saturated pack rust to a minimum of 250 °F and a maximum of 400 °F, or
• Using 35,000 psi ultra-high pressure water jet.
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Missouri• Calcium sulfonate rust penetrating sealer• Suitable for any steel structure that has developed
pack rusting in overlapping steel plates, joints or at bolted areas.
• Applied in accordance with SSPC-PA1.
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Missouri Continued.• Can be applied to
• bearings, • overlapping steel plates, • pin connections, • pin and hanger connections and • locations where
• rust bleeding, • pack rust, • layered rust occurs.
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WashingtonPack rust of 1/16 inch or greater.• Clean to a depth of ½ of the gap width, maximum of ¼ inch.• Cleaned gap treated with rust penetrating sealer.• Apply Caulk to form watertight seal.
If gap greater than ¼ inch • Gap should be filled with foam backer rod material.• Apply sealant over the backer rod.
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Task 3Pack Rust in Indiana Bridges
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Pack Rust in Indiana Bridges
•Gathered relevant pack rust information from Bridge inspection reports.
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Typical Members Affected by Pack Rust
•Bearings(Rocker, some cases Elastomeric)•Splice connections•Hinge-pin connection•Gusset plate and other connections•Beam cover plates•End diaphragms
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Bearings
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Pack Rust
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Pack Rust
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Pack Rust
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Pack Rust
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Splice plates
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Pack rust
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Pack rust
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Hinge-pin connection
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Pack Rust
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Pack rust
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Gusset plates, battens and angles
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Cover plates
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Diaphragms
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Cross bracing fallen down
Cross bracings connections
Pack rust
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Statistical Analysis on Data Collected
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• Total state owned steel bridges in 4 districts inspected – 1235• No. of bridges with some form of pack rust – 422
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56 %
43 %
22 %
31 %
0
10
20
30
40
50
60
Fort Wayne Crawfordsville Greenfield Seymour
Perc
enta
ge
Percentage of Bridges with Pack Rust
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61
48
2635
54
39
2028
69
3326
37
60
75
63
43
FORT WAYNE CRAWFORDSVILLE GREENFIELD SEYMOUR
BERC
ENTA
GE O
F BR
IDGE
S W
ITH
PACK
RU
ST
DISTRICTS
PERCENTAGE OF BRIDGES WITH PACK RUST BASED ON FEATURE
INTERSECTEDWater Body Road RR Abandoned RR
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70 2 2 4
34
94
0
127 6 7
42
60
105 4 0
14
36
50
010
0 112
28
46
NU
MBE
R O
F BR
IDGE
SMEMBER WISE COUNT
Fort Wayne Crawfordsville Greenfield Seymour
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48
18
45
17
29
8
19
12
21
SPLICE BEARING
PERC
ENTA
GE O
F O
CCU
RREN
CE
COMPARISON OF PERCENTAGE OCCURRENCE OF PACK RUST
Fort Wayne Crawfordsville Greenfield Seymour
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District wise Salt usage
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Annual Winter Maintenance Report FY 2013 by Phil Ivy
(lane-miles) salt (tons) (tons/lane-miles)
Fort Wayne 4,652 47000 10.1
Crawfordsville 4,699 44000 9.4
Greenfield 4,500 60000 13.3
Seymour 4,693 41500 8.8
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Splice plate pack rust in detail
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Rating 1Severe PR - > ¾ inch bowing of splices or bolt failure
Severity rating for pack rust in splices
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Rating 2Moderate to severe PR - ¼ to ¾ inch bowing of the splice plates
Rating 3Moderate PR – Visible bowing of the splice plates < ¼ inch of PR
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Rating 4Minor to moderate PR - Visible corrosion @ middle of splice Connection.
Rating 5Minor PR - Rust bleeding @ middle of splice Connection.
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0
5
10
15
20
25
30
35
40
45
0 1 2 3 4 5 6
Num
ber o
f yea
rs a
fter p
aint
ing
Pack Rust Severity
YEARS AFTER PAINTING VS. PACK RUST SEVERITY IN SPLICES (4DISTRICTS)
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12
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0
10
20
30
40
50
60
70
80
90
0 1 2 3 4 5 6
Avg.
age
at p
ack
rust
det
ectio
n
Pack rust severity
AGE AFTER BUILT VS. PACK RUST SEVERITY IN SPLICES (4DISTRICTS)
56
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21
17
12 13
16 15
6 7
11
6 5
7
0 0
25
14
FORT WAYNE CRAWFORDSVILLE GREENFIELD SEYMORE
PERC
ENTA
GE O
F BR
IDGE
S
PERCENTAGE OF BRIDGES WITH PACK RUST IN SPLICES OVER FEATURE
INTERSECTED DISTRICT BREAKUPWater Roads RR Abandoned RR
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15
10
7
9
WATER ROADS RR ABANDONED RR
PERC
ENTA
GE O
F BR
IDGE
S
FEATURE INTERSECTED
PERCENTAGE OF BRIDGES WITH PACK RUST IN SPLICES OVER FEATURE
INTERSECTED
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Trends for Cover Plates
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2.5
9.9
21
0
5
10
15
20
25
30
minor moderate severe
Age
ofpa
ck ru
st a
fter p
aint
ing
Condition
Cover plate condition vs age after painting
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Conclusions• Pack rust frequently occurs in Indiana bridges• Most common locations
• Bearings(top and bottom)• Splice plates (joints)• Hinge-pin connections• Gusset plates• Lower chords of truss
• No correlation between pack rust occurrence and salt usage.
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Conclusions• Common mitigation and repair methods
• Stripe coat• Caulking • Penetrating sealer (Promising mitigation and repair method)
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Ongoing Work• JRTP SPR 4309 Study initiated in 2019 to study pack rust
repairs• Using accelerated corrosion testing to examine pack rust
effects on splice connection detail• Examine different repair methods to determine which
methods are effective for use in Indiana
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Ongoing Work
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Ongoing Work
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Ongoing Work
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Ongoing Work
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Ongoing Work
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Questions ?