CONCRETE REINFORCEMENT –
CORROSION RESISTANT ALTERNATIVES
Florida Atlantic University
Department of Ocean Engineering
Overview of Factors Affecting Durability
of Concrete Bridge Structures
Environmental
Factors
1.
2.
3.
4.
5.
Material Factors
1.
2.
3.
4.
5.
6.
Temperature
Chlorides
Carbonation
Relative Humidity
Wet-Dry
Cement/Grout
Admixtures
Aggregates
Type of Reinforcement
Material Variability
Duct
Design/Construction
Factors
1.
2.
3.
4.
5.
Applicable Standards
Mix Design
Cover
Joints/Connections
Quality Control
The Case for Corrosion Resistant Reinforcement
Cumulative Corrosion Damage
Time to
Surface Cracking
Propagation
Period (ECR)
Uncertainty
~5y
~5y
Black
Steel
Corrosion
Initiation Time
(Black Bar and
ECR)
Uncertainty
Initiation Time
(CCR)
Time
Corrosion Rate
The Case for Corrosion Resistant
Alloys As Reinforcement
SS
6
Crit. Current Density
CS: Passive in
concrete/cement pore
water but with low Cltolerance
CS
8
pH
10
12
STAINLESS STEELS
•
•
14
- Potential +
CS
SS
6
8
10
pH
12
SS
CS
14
Log Current Density
Alloys w/ >12w/0 Cr.
More tenacious passive
film than carbon steel
(lower critical current
density).
Project Objective and Concerns
Susceptibility to Localized Corrosion
Objective: Characterize the performance
of different corrosion resistant
reinforcements in exposures relevant
to northern and coastal bridge
applications.
1. Pitting.
2. Crevice Corrosion.
Cumulative Cost
Life Cycle Cost
Concerns in Addition to ClDesign Life
SS
CS
Time
1. Carbonation.
2. Storage/Atm. Corrosion.
3. Galvanic Corrosion.
4. End Connections (Clad).
5. Torch Cuts/Welds.
6. Penetrations.
7. Product Variability.
Candidate Alloys






Type 304 SS
Type 316 SS
Type 2205 SS
Type 2201 SS+
Type 3Cr12 SS
Clad Type 316 SS


MMFX-II*+
Black Bar
1. Stelax*
2. SMI*
Note: Default testing condition is with bars as-received.
* Testing in the surface abraded and surface damaged conditions.
+ Testing in the pickled condition.
Project Tasks
Short-Term Experiments:
 AST-1
Wet-Dry Exposure
 AST-2 A
Potentiostatic Tests
 AST-2 B
Potentiodynamic Polarization Scans

Atmospheric Exposures
Long-Term Experiments:
 Reinforced Concrete Slab Exposures
AST-1 Wet-Dry Experiments
(Modeled after Previous FHWA/WJE Program)



Weight % NaCl

Multiple 152 mm long #5 rebar specimens in asExposure Tank
received condition (selected materials bent,
abraded, surface damaged, and pickled).
Repetitive 1.75 hrs wet – 4.25 hrs
Holding Tank
dry cycle (four cycles per day) in simulated pore
water (pH~13.2).
Incrementally increasing NaCl concentration
with time.
Total exposure duration 84 days.
15%
15%
10%
9%
5%
3%
0%
0
15
30
45
Time, days
60
75
90
Specimens in Exposure Tank
AST-1 Data Correlation
Corrosion Rate (WL), mpy
100
10
1
Black Bar
316 ss
2205 ss
2201 ss
2201 P ss
MMFX
Stelax
0.1
0.01
0.01
0.1
1
Corrosion Rate (RP), mpy
10
100
Corrosion Rate versus Time for Straight Bars: AST-1
1
16
Corrosion Rate, mmpy
0.1
12
10
0.01
8
Stelax (2)
316
MMFX (2)
2201 (2)
2205 (2)
Black (2)
2201 P(2)
NaCl
0.001
0.0001
0
10
20
30
40
50
Time, days
60
70
80
90
6
4
2
0
100
NaCl Concentration, percent
14
AST-2 Specimen and Test Cell
Electrical
Connection
0.40
Exposed
Circumferential
Surface
1.20
2.0
Dimensions in
inches
SCE
Epoxy
0.625
Specimen
Counter
Electrode
Mesh
AST-2 Potentiodynamic Polarization Experiments
Anodic scans performed on individual candidate
specimens in saturated Ca(OH)2 with various chloride
concentrations.
1.2
1
Potential (V vs. Eref)

0.8
0.6
CP-MMFX-C0f
CP-MMFX-C3a
CP-MMFX-C5a
CP-MMFX-C10a
0.4
0.2
0
-0.2-10.0
-8.0
-6.0
-4.0
-0.4
-0.6
-0.8
Log Current density ( A/cm2)
-2.0
0.0
AST-2B Potentiodynamic Polarization Scan Results
0.80
Critical Pitting Potential, V (SCE)
0.60
304
0.40
0.20
2201 P
0.00
2201 AR
-0.20
MMFX
3Cr12
-0.40
-0.60
0
1
2
3
4
5
6
NaCl Concentration, weight percent
7
8
9
10
Distributed Nature of the Critical Pitting Potential
1.0
Cumulative Fraction
0.8
0.6
2201 SS
2201P SS
MMFX
3Cr12
304 SS
0.4
0.2
0.0
-0.1
0
0.1
0.2
0.3
0.4
Pitting Potential, V SCE
0.5
0.6
0.7
Corrosion Resistance Reinforcement As an Alternative
to Conventional Structural Steel for Corrosive Applications –
AST-2 (Electrochemical Testing)
A. Triplicate specimens in SPW+[Cl-]low at RT
and constant potential. Monitor applied
current. Incrementally increase [Cl-].
Retrieve bars once critical chloride
concentration is reached.
DAS
B. Repeat (A) at pH = 9.
C. Repeat (A) and (B) at 40oC.
Potentiostat
D. Correlate w/ results from 1) WJE test
program, 2) AST-1, and 3) LLT.
_________
RE
CE
AST-2 Rationale
Potential, mVSCE
Increasing
Cl-
+100
0
-100
Critical ClConcentration
-200
Current Density
0.00020
9.00
8.00
3Cr12
MMFX B
7.00
MMFX B D
MMFX B A
6.00
MMFX A
MMFX
5.00
MMFX D
2201
0.00012
4.00
0.00008
0.00004
0.00000
0
200
400
600
800
Exposure Time (hours)
1000
1200
Cl- (w%)
Current Density (A/cm2)
0.00016
BB
2201 P
Stelax D
3.00
SMI A
SMI D
2.00
SMI
Stelax B
1.00
Stelax A
Stelax
0.00
316
304
1400
2205
Cl- (w%)
Test Yard Exposure of Deck Slabs
Potential Data, Black Bar Set 1
0
-50
Potential, V (SCE)
-100
-150
1-STD2-BB-1
-200
1-STD2-BB-2
-250
1-STD2-BB-3
-300
1-STD1-BB-1
-350
1-STD1-BB-2
-400
1-STD1-BB-3
-450
-500
-550
-600
-650
0
25
50
75
100
125
150
175
200
Exposure Time, days
225
250
275
300
325
350
Potential Data, Set 1 Straight Bars
0
1-STD1-316-1
-50
1-STD1-316-2
-100
1-STD1-316-3
1-STD1-2201-1
Potential (mV ref SCE)
-150
1-STD1-2201-2
-200
1-STD1-2201-3
-250
1-STD1-MMFX-1
-300
1-STD1-MMFX-2
1-STD1-MMFX-3
-350
1-STD1-Stelax-1
-400
1-STD1-Stelax-2
-450
1-STD1-Stelax-3
-500
1-STD1-BB-1
1-STD1-BB-2
-550
1-STD1-BB-3
-600
1-STD1-3Cr12-1
1-STD1-3Cr12-2
-650
0
25
50
75
100
125
150
175
200
Exposure Time, days
225
250
275
300
325
350 1-STD1-3Cr12-3
Current Density Data, Set 1 Straight Bars
2.00E+00
1-STD1-316-1
µ A/cm^2
1-STD1-316-2
1-STD1-316-3
1.50E+00
1-STD1-2201-1
1-STD1-2201-2
1-STD1-2201-3
1-STD1-MMFX-1
Current Density,
1-STD1-MMFX-2
1-STD1-MMFX-3
1.00E+00
1-STD1-Stelax-1
1-STD1-Stelax-2
1-STD1-Stelax-3
1-STD1-BB-1
1-STD1-BB-2
5.00E-01
1-STD1-BB-3
1-STD1-3Cr12-1
1-STD1-3Cr12-2
1-STD1-3Cr12-3
0.00E+00
0
25
50
75
100
125
150
175
Exposure Time, days
200
225
250
275
300
Potential Data, Set 2 Cracked Concrete
0
-50
Potential, mV (SCE)
-100
-150
2-CCNB-316-1
-200
2-CCNB-316-2
2-CCNB-316-3
-250
2-CCNB-2201-1
-300
2-CCNB-2201-2
2-CCNB-2201-3
-350
2-CCNB-MMFX-1
-400
2-CCNB-MMFX-2
-450
2-CCNB-MMFX-3
-500
-550
-600
-650
0
25
50
75
100
125
150
175
200
Exposure Time, days
225
250
275
300
325
350
Potential-Current Density Format
0
-200
-300
-400
-500
-600
1-STD2-BB-1
1-STD2-BB-2
1-STD2-BB-3
1-STD1-BB-1
1-STD1-BB-2
1-STD1-BB-3
3-CCON-BB-1
3-CCON-BB-2
3-CCON-BB-3
0
-700
1.00E-04
1.00E-03
1.00E-02
1.00E-01
Current Density, mA/cm^2
1.00E+00
1-STD2-MMFX-1
1-STD2-MMFX-2
1.00E+01
1-STD2-MMFX-3
-100
1-STD1-MMFX-1
1-STD1-MMFX-2
1-STD1-MMFX-3
-200
3-CCON-MMFX-1
3-CCON-MMFX-2
3-CCON-MMFX-3
-300
3-CCRV-MMFX-1
3-CCRV-MMFX-2
3-CCRV-MMFX-3
-400
3-CREV-MMFX-1
3-CREV-MMFX-2
3-CREV-MMFX-3
-500
2-PICK-MMFX-1
2-PICK-MMFX-2
2-PICK-MMFX-3
-600
2-BCAT-MMFX-1
2-BCAT-MMFX-2
2-BCAT-MMFX-3
-700
2-CCNB-MMFX-1
1.00E-042-CCNB-MMFX-2
1.00E-03
2-CCNB-MMFX-3
Potential, V(SCE)
Potential, V (SCE)
-100
1.00E-02 1.00E-01 1.00E+00 1.00E+01
Current Density, µA/cm2
Potential – Current Density Trend
0
-100
2201P - Set 2
Potential, V (SCE)
-200
2201AR - Set 1
2201BCAT - Set 2
-300
2201CCON - Set 3
-400
MMFX - Set 2
-500
Black bar - Set 1
-600
-700
0.0001
0.001
0.01
0.1
Current Density,µA/cm^2
1
10
Present Project Status







Approximately 3 years into a six year effort.
Atmospheric exposures to be initiated.
AST-1 and -2A exposures to be completed.
AST-2B exposures completed.
Slab monitoring to continue.
Correlations between accelerated, short-term exposures and long-term
concrete slab exposures to be developed.
Life cycle modeling as a function of HPMR type and exposure severity
to be developed.