Improved Test Methods & Practices for Characterizing Steel Corrosion

Potential of Earthen Materials

2019 Midwest Geotechnical

Engineering Conference

Crown Plaza

Columbus, Ohio

September 18, 2019

NCHRP 21-11 Update

PI : Ken Fishman, Earth Reinforcement Testing, Division of

McMahon & Mann Consulting Engineering and

Geology, P.C.

Co-PI : Soheil Nazarian, University or Texas, El Paso

1

NCHRP 21-11 WORKPLAN

• PHASE I (Tasks 1-4) – Collect Existing Information• Identify knowledge gaps

• Develop a detailed work plan to improve methods for sampling and testing and characterization of corrosiveness of earthen materials.

• PHASE II (Tasks 5 & 6) – Implement Work Plan Developed in Phase I• Study Laboratory and field tests for measurement of electrochemical

parameters, and characterizing steel corrosion

• Draft protocol for characterizing corrosiveness of earthen materials

• Formulate a detailed work plan to evaluate practical application of proposed protocol

NCHRP 21-11 WORKPLAN (Continued)

• Phase III (Tasks 7, 8 & 9) – Implement Work Plan Developed in Phase II.

• Conduct trails in active construction projects• Shadow specification to compare with current practice• Demonstrate and evaluate recommendations and protocols

for sampling, testing and characterizing corrosiveness of earthen materials.

• Initiate training with personnel from State DOTs

QUESTIONS

• How do results obtained from different test methods compare?

• How fine does the material need to be before testing the fraction passing the #10 sieve is appropriate?

• How can the test results be combined to characterize corrosion potential?

• How well does the proposed characterization of corrosion potential compare with performance?

• Is testing an aqueous extract (leachate) appropriate for coarse materials?

4

SUMMARY OF RESULTS

• Justify recommendations for draft protocol

• Comparisons between test results and identification of trends

• Comparisons between characterizations of corrosivity and performance

• Identify alternatives for coarse open graded materials

• Identify needs for further study of unconventional materials

5

Site Information/Samples

7

0%

20%

40%

60%

80%

100%

Flo

rid

a

EL

Paso

MS

E

M-U

-D N

Y

So

uth

Caro

lin

a L

WF

PIP

@ 1

5ft

PIP

@ 1

0ft

So

uth

Caro

lin

a G

B

PIP

@ 5

ft

Ph

arr

TX

Lo

usia

na L

WF

Cru

sh

ed

Ro

ch

este

r N

Y

El P

aso

TX

Cala

gary

AB

Pri

nce G

eo

rge B

C

Ash

do

wn

AR

Tem

ple

TX

Sp

rain

Bro

ok N

Y

Rale

igh

NC

Gard

en

Cit

y T

X

Map

le R

d N

Y

Wake F

ore

st

NC

Ro

un

d R

ock T

X

Lo

usia

na L

WF

Un

cru

sh

ed

Waco

TX

El P

aso

Co

ars

e M

SE

San

An

ton

io

Bastr

op

Fine Medium Coarse

Co

mp

osit

ion

, %

Material Source

Gravel Coarse Sand Fine Sand Fines

Material Composition

CONSIDERATIONS FOR SELECTION OF TEST METHODS

1. Precision and repeatability of test methods.

2. Compatibility between parameters – e.g., salt contents and resistivity

3. Correlations between resistivity measurements, corrosivity and corrosion rates

4. Utility of test results

8

Resistivity

Test Method Aggregate Size Preparation Box Size

AASHTO T288 (Standard) Passing #10Mix with 150 ml, let

stand for 12 hrs.Small

ASTM G187 As is, remove

particles greater

than ¼”

Start as is Small

ASTM WK 2461 As isSaturate and wait

24 hrs.

Small medium, or large

(depending on maximum

aggregate size)

TX-129-E (Small Box Method) Passing #8 Start dry Small

TX-129-M (Big Box Method) As is Start dry

Small medium, or large

(depending on maximum

aggregate size)

RESISTIVITY TESTS

TEST STANDARD SEPARATION MOISTURE

CONDITIONS

CURE PERIOD BIAS w.r.t.

AASHTO T-288

PRECISION

µCOV (%)

AASHTO T-288 #10 increments 12 hours for 1st

increment

- 4.6

TEX-129-E #8 increments None 1.07 3.2

ASTM G-187 ¼ inch As-is or

saturated

None 1.41 5.3

TEX-129-M none increments, but

saturated for

coarse materials

None 2.28 4.8

ASTM WK24621 none Drained from a

saturated

condition

Soak for 24

hours before

draining

3.75 7.4

10

PUBLISHED PRECISION & BIAS FOR ASTM G-187

Soil #1 Soil #2 Soil #3

Average Resistivity (Ω-cm) 2296.95 450.10 19577.14

Repeatability Standard Deviation, s, (Ω-cm) 105.78 40.82 1194.95

Repeatability Coefficient of Variation, COV, % 4.6 9.1 6.1

Reproducibility Standard Deviation, s, (Ω-cm) 318.4 40.82 1721.30

Reproducibility Coefficient of Variation, COV, % 13.9 9.1 8.8

From ILS in Tampa Florida on November 18, 2003. Triplicate soil resistivity measurements by seven participants.

11

12

y = 0.9614x

R² = 0.9543

0.0

5000.0

10000.0

15000.0

20000.0

0.0 5000.0 10000.0 15000.0 20000.0

Tex-

12

9-E

(Ω

-cm

)

AASHTO T-288 (Ω−cm)

AASHTO T-288 vs. Tex-129-E

y = 1.1484x

R² = 0.8835

0.0

5000.0

10000.0

15000.0

20000.0

0.0 5000.0 10000.0 15000.0 20000.0

AST

M G

18

7 (

Ω-c

m)

AASHTO T-288 (Ω−cm)

AASHTO T-288 vs. ASTM G 187

0.0

5000.0

10000.0

15000.0

20000.0

25000.0

30000.0

35000.0

40000.0

0.0 10000.0 20000.0 30000.0 40000.0

Tex-

12

9-M

(Ω

-cm

)

AASHTO T-288 (Ω−cm)

AASHTO T-288 vs. Tex-129-M

BIAS OF RESISTIVTY MEASUREMENTS AS A FUNCTION OF TEXTURE

0

1

2

3

4

5

6

7

Fine Sand Coarse Sand Gravel

BIA

S

MATERIALS

Tex-129-E ASTM G187 Tex-129-M ASTM WK24621

13

Effect of Texture on Resistivity

The resistivity measurements vary with respect to coarseness of the sample, especially for the TX-

620-M, TX-129-M and ASTM WK2461 test methods. In general, for the same materials, the

measurements of resistivity vary with respect to test methods, however, results from AASHTO T 288

and TX-129-E method are similar for each material.

0.0

5000.0

10000.0

15000.0

20000.0

25000.0

30000.0

35000.0

40000.0

45000.0

50000.0

AASHTO T-288 Tex-129E G-187 Tex-129M ASTM WK-2461

RE

SIS

TIV

ITY

(Ω

-cm

)

TEST METHOD

Florida

EL Paso MSE

M-U-D NY

South Carolina LWF

PIP @ 15ft

PIP @ 10ft

South Carolina GB

PIP @ 5'

Pharr TX

Rochester NY

El Paso TX

Calagary AB

Raleigh NC

Prince George BC

Temple TX

Sprain Brook NY

Maple Rd NY

Wake Forest NC

Round Rock TX

El Paso Coarse MSE

15

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

9.00

0.001 0.010 0.100 1.000

Bia

s Te

x-1

29

-M/A

AS

HTO

T-2

88

d2#10*nT288*100/(n129-M*(wg*d2

g+wcs*d2cs+wfs*d2

fs+wf*d2f))

Fine Sand

Coarse

SandGravel

TRENDING OF BIAS FROM TEX-129-M

16

Sample

Types

Bias < 1.5 1.5 < Bias < 3.0 Bias > 3

GN PP #10 GN PP #10 GN PP #10

Gravel - - 1.99 – 3.00 6- 40 3.00 – 3.56 24 - 40

Coarse

Sand

4.48- 4.83 60 - 70 3.85 - 4.48 50 - 60 - -

Fine Sand 5.00 - 6.65 > 80 - - - -

GN &PP #10 CORRESPONDING TO BIAS TRENDS

CONCLUSIONS

1. IF PP #10 > 60% then BIAS ≈ 1

2. IF GN > 3 and PP #10 < 40% then BIAS > 3

• corresponds to gravels with a coarse sand component ≈ 30%

Tests on Leachate

Test Aggregate Size Soil to Water Ratio Set up

SCDOT T143 Passing 1 ½” ~ 1:4Large plastic

container with lid

TX-620-J Passing #40 1:10Stirring plate and

stirring bar

TX-620-M Passing 1 ¾” 1:10Roller and 2-Liter

plastic bottle

MEASUREMENTS OF SULFATE CONTENT

TEST

STANDARD

SEPARATION DILUTION

RATIO

HEATED MIXING FILTRATION PRECISION

µCOV (%)

AASHTO T-290 #10 1:3 NO SHAKEN CENTRIFUGE

& FILTER

10.1

TEX-620-J #40 1:10 140°F

STIR EVERY

HOUR FOR 12

HOURS

FILTERED 11.8

TEX-620-M NONE 1:10 NO MIXED FOR

60 MINUTES

FILTERED 10.7

18

MEASUREMENTS OF CHLORIDE CONTENT

TEST

STANDARD

SEPARATION DILUTION

RATIO

HEATED MIXING FILTRATION PRECISION

µCOV (%)

AASHTO T-291 #10 1:3 NO

SHAKE

FOR 20 SEC,

STAND FOR 1

HOUR, SHAKE

CENTRIFUGE

& FILTER

7.5

TEX-620-J #40 1:10 140°F

STIR EVERY

HOUR FOR 12

HOURS

FILTERED 3.7

TEX-620-M NONE 1:10 NO MIXED FOR

60 MINUTES

FILTERED 12.9

19

20

620-M (mg/kg) = 0.71(T-290)

R² = 0.79

620-M (mg/kg) = 0.51(T-291)

R² = 0.76

0

100

200

300

400

500

600

700

800

900

1000

0 100 200 300 400 500 600 700 800 900 1000

Tex

-62

0-M

(m

g/k

g)

AASHTO T-290 & 291 (mg/kg)

Sulfate

Chloride

Linear (Sulfate)

Linear (Chloride)

CORRELATIONS BETWEEN SALT CONTENT MEASURMENTS

21

Bias = 0.06(PP#10)0.64

R² = 0.76

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0 10 20 30 40 50 60 70 80 90 100

62

0-M

cl+

0.6

5*

62

0-M

SO

4/(

0.6

5*

T2

90

+T

29

1)

PP#10 (%)

>60%

CORRELATION BETWEEN BIAS FROM SALT CONTENT MEASUREMENTS AND PP #10

<25%

CONCLUSIONS

1. PP #10 < 25%

= lowest bias

2. PP #10 > 60%

= bias > 1

OBSERVATIONS FROM MEASUREMENTS OF SALT CONTENTS

• Precision/repeatability of test methods evaluated in this study for measurements of salt contents are similar.

• Bias statistics describing how salt contents measured via other test methods compare to those measured from the current the AASHTO tests are dependent upon material characteristics including texture as gravel, coarse sand, or fine sand.

22

23

100

1000

10000

100000

1 10 100 1000 10000

Re

sist

ivit

y (

Ω-c

m)

Equivalent Salt Content (mg/kg)

Wake Forest, NC

Ocala, FL

South Carolina LWF

Prince George, BC

Ashdown, AR

Round Rock, TX

M-U-D, NY

Raleigh, NC

South Carolina GB

Maple Road, NY

Pharr, TX

Sprain Brook NY

Garden City, TX

El Paso MSE Fine

El Paso MSE Coarse

El Paso, TX

Rochester, NY

Calgary, AB

Temple, TX

PIP, NY @ 15 feet

Louisiana LWF Uncrushed

Bastrop, TX

Louisiana LWF Crushed

Waco, TX

Chloride

minus 25 % error

plus 25% error

Equivalent Salt Content vs. Resistivity

with

AASHTO (PP #10 > 22%) or Texas Modified (PP#10 < 22%)

Wake

RR

GCEl Paso – MSE Coarse

24

y = 142105x-1.1

R² = 0.88

100.00

1000.00

10000.00

100000.00

0.01 0.10 1.00 10.00 100.00

Re

sist

ivit

y Te

x-6

20

-M (

Ω-c

m)

Total Salt Content Tex-620-M (mEq)

y = 13488x-0.82

R² = 0.64

100.0

1000.0

10000.0

100000.0

1.00 10.00 100.00R

esi

stiv

ity

AA

SH

TO

T-2

88

(Ω-c

m)

Total Salt Content AASHTO (mEq)

Total Salt (mEq) = ppm ÷ equiv. atomic weight = Cl-(kg/mg) ÷ 35.5 + SO4 (kg/mg) ÷ 48. + HCO3 (kg/mg)÷ 61

CORRELATION BETWEEN TOTAL SALT CONTENT

and RESISTIVITY MEASUREMENTS

pH MEASURMENTS

TEST

STANDARD

AIR

DRY

SEPARATION DILUTION

RATIO

HEATED MIXING STAND

TIME

PRECISION

µCOV (%)

AASHTO T-289 Y #10 1:1 N Stir every 10-15 min

for 1 hour

NONE 1.0

ASTM D 4972 Y #10 1:1 N Mix thoroughly 1 HR 1.1

NCHRP 21-06 N 3/8 IN 1:1 N Stirred 30 MIN 0.7

TEX-129-E Y #40 1:5 Y Stir every 15 min. for

1 hour

NONE 0.9

TEX-620-M Y NONE 1:10 N Agitate for 1 hour NONE 1.2

25

26

21-06 = 0.98 (T-289)

R² = 0.70

5.0

6.0

7.0

8.0

9.0

10.0

5.0 6.0 7.0 8.0 9.0 10.0NC

HR

P 2

1-0

6 (

pH

)

AASHTO T-289 (pH)

D 4972 = 0.99(T-289)

R² = 0.69

5.0

6.0

7.0

8.0

9.0

10.0

5.0 6.0 7.0 8.0 9.0 10.0

AST

M D

49

72

(p

H)

AASHTO T-289 (pH)

128-E = 1.03(T-289)

R² = 0.63

5.0

6.0

7.0

8.0

9.0

10.0

5.0 6.0 7.0 8.0 9.0 10.0

Tex-

12

8-E

(p

H)

AASHTO T-289 (pH)

Tex-620-M = 1.08(T-289)

R² = 0.33

5.0

6.0

7.0

8.0

9.0

10.0

5.0 6.0 7.0 8.0 9.0 10.0

Tex-

62

0-M

(p

H)

AASHTO T-289 (pH)

COMPARISON of pH MEASURMENTS RELATIVE TO AASHTO T-289

27

0

2

4

6

8

10

1.03 1.05 1.07 1.10 1.12 More

Fre

qu

en

cy

Bias - Tex-620-M/AASHTO T-289

CONCLUSIONS• Measurements of pH from Tex-620-M are less repeatable compared to measurements from

other test standards.

• In general, Tex-620-M renders pH that are higher compared to the pH values from the other

test standards included in the study.

• Results from NCHRP 21-06 are more repeatable compared to AASHTO T-289 and do not

have a significant bias with respect to results from AASHTO T-289.

DISTIBUTION of BIAS FROM pH MEASURMENTS

28

CR = 2877ρ-0.73

R² = 0.50

0

5

10

15

20

25

30

35

40

45

0 2000 4000 6000 8000 10000 12000 14000 16000 18000 20000

Co

rro

sio

n R

ate

(µ

m/y

r)

Resistivity (Ω-cm)

Ocala, FL

South Carolina LWF

Ashdown, AR

M-U-D, NY

Raleigh, NC

South Carolina GB

El Paso, TX

Rochester, NY

Sprain Brook NY

El Paso MSE Fine

PIP, NY @ 15 feet

Power (Trendline)

CR = 5267ρ-0.84

R² = 0.62

0

5

10

15

20

25

30

35

40

0 10000 20000 30000 40000 50000

Me

asu

red

CR

(µm

/yr)

Resistivity (Ω-cm)

CORROSION RATES & RESISTIVITY MEASUREMENTS FROM

AASHTO T-288 WITH > 22% PASSING #10

Data from NCHRP 21-11

Worldwide Data

PROPOSED PROTOCOL

1. IF GN > 3 or PP #10 > 25%

• AASHTO T-288, T-289, T-290 & T-291

2. IF GN < 3 and PP # 10 < 25%

• Tex-129-M, Tex-620-M

• ??? Considering using NCHRP 21-06 for pH ???

3. Consider alternatives for very coarse, open graded material

29

Summary of Screening Techniques and Characterizations

UNIVARIATE – Binary Systems MULTIVARIATE1. AASHTO (1992) - Galvanized Steel 1. German DVGW GW 9 –Pipelines

2. PTI – Prestressing Steel (High Strength) 2. AWWA (DIP) – 10 Point Method

3. Burec (2009) Resistivity - 10th Percentile – DIP

and CIP

3. Jones (1985) – steel soil reinforcements

4. FHWA (2003) – Solid Bar Soil Nails – Carbon

Steel

4. Clouterre (1993) – Soil Nails

5. European Standard – EN 12501-2 (2003) 5. Brady and McMahon (1994), UK – Galvanized

steel structures/Culverts

6. Beavers and Durr (1998), NACE (2001) – Steel

Piles

7. AGA (1983) – Hot-dipped Galvanized Steel

8. Demisse (2015) - Bayes Network - waterlines 30

Parameter AASHTO Test

Method

Requirement

ρmin T 288 >3000 Ω-cm

pH T 289 5 to 10

Sulfates T 290 <200 ppm

Chlorides T 291 <100 ppm

AASHTO Electrochemical

Requirements for Mechanically

Stabilized Earth Fill Used with

Galvanized Steel

Reinforcements

Criteria Used in

the US for

Assessing Ground

Corrosion

Potential Relative

to SBSN’s (after

FHWA, 2003)

31

German Gas and Water Works Engineers’ Association Standard (DVGW GW9)

32

ITEM MEASURED VALUE MARKS

Soil

Composition

Calcareous, marly limestone, sandy marl,

not stratified sand

+2

Loam, sandy loam (loam content 75% or

less), marly loam, sandy clay soil (silt

content 75% or less)

0

Clay, marly clay, humus -2

Peat, thick loam, marshy soil -4

Ground water

level at buried

position

None 0

Exist -1

Vary -2

Resistivity

> 10,000 Ω-cm 0

5000 Ω-cm – 10,000 Ω-cm -1

2300 Ω-cm – 5000 Ω-cm -2

1000 Ω-cm – 2300 Ω-cm -3

> 10000 Ω-cm -4 33

ITEM MEASURED

VALUE

MARKS

Moisture Content 20% or less 0

20% or more -1

pH 6 or more 0

6 or less -2

Sulfide and

Hydrogen Sulfide

None 0

Trace -2

Exist -4

Carbonate

5% or more +2

1% to 5% +1

< 1% 0

Chloride

< 100 ppm 0

> 100 ppm -1

34

ITEM MEASURED VALUE MARKS

Sulfate

< 200 ppm 0

500 ppm – 200 ppm -1

1000 ppm – 500 ppm -2

> 1000 ppm -3

Cinder

& Coke

None 0

exist -4

SCORE CHARACTERIZATION

> 0 Noncorrosive

0 to -4 Slightly Corrosive

-5 to -10 Corrosive

< -10 Very Corrosive

DVGW GW9 –

Characterization of Corrosivity

35

Total

Score

General

Corrosion

Rate

Range Localized

(Pitting)

Corrosion

Rate

Range

µm/yr µm/yr

≥ 0 Ia 5 2.5 – 10 30 15 – 60

-1 to -4 Ib 10 5 – 20 60 30 – 120

-5 to -10 II 20 10 – 40 200 100 – 400

< -10 III 60 30 - 120 400 200 - 800

Soil Corrosivity/Aggressiveness

(Carbon Steel) DIN 50 929 Part 3

36

37

Sample GN #10 Test

Method

(Proposed

Protocol)

Corros.

RankA

(I)

CR

(µm/yr)

Cluster

Galv. Plain

San Antonio, TX 0.18 2 Tex-129-M 1.0 NAB

No

t Co

rrosiv

e

(I) ≥

0

Wake Forest, NC 2.21 8 Tex-129-M 2 0.3 < 0.1

Bastrop, TX 0.15 2 Tex-129-M 2 0.4 NA

Ashdown, AR 2.88 36 AASHTO T-288 2 1.8C NA

TTC, NC 3.51 24 AASHTO T-288 1 5.8 1.6

Ocala, FL 5.65 91 AASHTO T-288 0 1.8 3.8

LWF, South

Carolina

4.83 68 ASTM

WK 24261

0 1.2 8.4

El Paso

Coarse/MSE

0.22 2 Tex-129-M 0 0.2 NA

Waco, TX 1.26 7 Tex-129-M 0 0.3 NA

M-U-D, NY 5.24 82 AASHTO T-288 -1 4.8 39 Slig

htly

Co

rrosiv

e

-3 ≤

(I) <

0

Garden City, TX 2.52 22 Tex-129-M -1 4.3 NA

GB, South Carolina 4.48 56 AASHTO T-288 -1 3.2D 5.8

Maple Rd., NY 2.50 22 Tex-129-M -2 3.7 16

El Paso Fine/MSE 5.52 87 AASHTO T-288 -2 21E NA

Prince George, BC 2.89 32 AASHTO T-288 -3 NA 20

PIP, NY 4.62 61 AASHTO T-288 -4 37 30

Co

rrosiv

e

-5 ≤

(I) <

-3

Sprain Brook Pkwy,

NY

2.54 27 AASHTO T-288 -4 33 NA

Quarry; El Paso, TX 3.64 41 AASHTO T-288 -4 14.8 NA

Rochester, NY 3.85 49 AASHTO T-288 -5 9.6 20

Data Clustering Relating

Corrosivity Rankings to

Observed Rates of

Corrosion

Corrosivity Clusters Observed Corrosion Rates, CR

Galvanized Plain Steel

(I) ≥ 0 CR < 2 µm/yr CR < 5 µm/yr

-3 ≤ (I) < 0 2 µm/yr < CR < 5 µm/yr 5 µm/yr < CR < 20 µm/yr

-5 ≤ (I) < -3 10 µm/yr < CR < 35 µm/yr 20 µm/yr < CR < 40 µm/yr

NCHRP 21-11 – PHASE III

• Phase III (Tasks 7, 8 & 9) – Implement Work Plan Developed in Phase II.

• Conduct trials in active construction projects• Shadow specification to compare with current practice• Demonstrate and evaluate recommendations and protocols

for sampling, testing and characterizing corrosiveness of earthen materials.

• Initiate training with personnel from State DOTs

38

Conduct Field Tests to Support Recommended Specifications for New

Methodology

• Identify fill source prior to construction

• Relevant activities include:• Sampling the materials before construction

• Sampling the materials during compaction

• Conducting field resistivity for comparison to the lab resistivity

• Conducting moisture-density tests with help of DOT

• Conduct index and electrochemical tests on:• Materials collected before construction

• Materials collected during construction

39

Insitu Soil Testing

Calgary, AB

Marcy – Utica – Deerfield, NY

• Stevens Hydraprobe uses a five-tine probe

that can measure the subsurface moisture

content and conductivity which can be

converted into resistivity

• The Wenner 4-electrode method (ASTM G-57)

measures the resistivity of the subsurface by

inserting 4 equally spaced electrodes into

the ground in a line, applying an electric

current between two outer electrodes, and

measuring the corresponding voltage drop

between the inner electrodes.

COARSE GRAINED SAMPLE AT SATURATION

41

REMARKS

• Consistent trends are observed between results obtained with different test methods and between materials with different textures

• Salt contents are a good check on measured resistivity

• AASHTO Test Methods apply well to materials with more than 25% passing the #200 sieve.

• TX-129-M and TEX-620-M apply well to coarse materials

• Results from TX-129-M and TEX-620-M can be correlated

• Good correlation between observed performance (CR’s) and characterization of corrosion potential based on resistivity measurements.