as a Replacement for Epoxy

ovariesracialUrban and Civil

Nov 25, 2013 (3 years and 7 months ago)

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Stainless Steel Reinforcement
as a Replacement for Epoxy
Coated Steel in Bridge Decks

ODOT
-
OkTC

Transportation Research Day

Oklahoma City, OK

October 12, 2013

Outline

Objectives

Reinforcement

Test methods and Results

Life expectancy and Cost
-
effectiveness

Conclusions and Recommendations


Determine the corrosion resistance of 2304 duplex
stainless steel reinforcement and NX
-
SCR™
stainless steel clad bars compared to conventional
and epoxy
-
coated reinforcement in reinforced
concrete bridge decks


Estimate the life expectancy and cost effectiveness
of 2304 duplex stainless steel, NX
-
SCR™ stainless
steel clad reinforcement, epoxy
-
coated
reinforcement, and mild steel reinforcement in
bridge decks in Oklahoma

Objectives

Reinforcement

Conv.


ECR


2304


SS Clad

2304






Pickled a second time








As delivered

Test Methods

Rapid Macrocell test

Southern Exposure test

Cracked Beam test

Chloride Induced Corrosion

Two phase process:

Phase I


initiation


Time to reach the
critical chloride
corrosion threshold

Phase II


corrosion


Corrosion products
build up around
reinforcement



Time
Corrosion Loss
Phase I

Phase

II

Cracking of Concrete

Measurements and observations

Voltage drop to measure corrosion rate

Corrosion potential

Mat
-
to
-
mat resistance

Linear Polarization to measure microcell
and macrocell corrosion

Cl


content at corrosion initiation

Cracking and staining of concrete

Corrosion on bars following tests

Evaluate disbondment of epoxy coating

Bench
-
Scale Tests

Southern Exposure Test

10 ohm
Termi nal Box
Vol tmeter
15
% NaCl sol uti on
12.0 i n.
2.25 i n.
2.5 i n.
2.5 i n.
2.5 i n.
2.25 i n.
1.0 i n.
1.0 i n.
7.0 i n.
V
Cracked Beam Test

V
Voltmeter
Terminal Box
10 ohm
6.0 in.
1.0 in.
1.0 in.
7.0 in.
All bars


Southern Exposure

Corrosion resistant bars


Southern
Exposure, different scale

Critical Chloride Corrosion Threshold

Reinforcement

No. of
Samples

Avg.
Initiation

Age

(weeks)

Avg.
Chloride
Content

(lb/yd
3
)

Conventional

34

12.5

1.78

Conv./2304

18

8.0

1.76

Conv./SSClad

26

9.3

1.59

ECR

36

16.5

4.59

SSClad
-
4h

54

26.7

7.62

SSClad

--

--

--

2304

35

99.8

20.5

2304/Conv.

14

75.0

20.5

All bars


Cracked Beam

Corrosion resistant bars


Cracked
Beam, different scale

2304


Cracked Beam

2304 (pickled a second time)



Cracked beam


SS Clad


Cracked Beam

Cracked beams


Conv. ECR 2304 SS clad

Comparisons based on:

150 ft span, 42 ft width, 8 in. deck

75 and 100
-
year economic lives

ODOT costs



Time to first repair (years)

2 ½
-
in. cover

Steel

Designation

Initiation

Initiation
to
Cracking

Cracking


to Repair

First
Repair

Conventional

2.1

7

10

19

ECR

8.4

35

10

53

2304

44

26

10

80

2304
-
p

--

--

10

> 100

SSClad

--

--

10

>

100

Costs per
yd
2


Present worth for 2% discount rate


Steel

Designation

Initial

Cost

Total costs

75 years

100 years

Conventional

$163

$1048

$1265

ECR

$198

$422

$422

2304

$275

$275

$423

2304
-
p

$275

$275

$275

SSClad

$240

$240

$240

Conclusions and
Recommendations

Corrosion resistant steels, even when
damaged, provide significant
advantages over conventional
reinforcement


Lack of proper pickling reduces
corrosion resistance of stainless steel




Conclusions and
Recommendations

Some problems with
NX
-
SCR
TM

stainless steel clad reinforcement


the bars are not currently available


Stainless steel reinforcement should
be pickled to a bright or uniformly light
surface to ensure proper performance



The University of Kansas


David Darwin, Ph.D., P.E.


Deane E. Ackers Distinguished Professor and Chair

Dept. of Civil, Environmental & Architectural Engineering

2150 Learned Hall

Lawrence, Kansas, 66045
-
7609

(785) 864
-
3827 Fax: (785) 864
-
5631


daved@ku.edu