NCHRP 21-11 Update Improved Test Methods & Practices for - - PowerPoint PPT Presentation

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% Florida EL Paso MSE M-U-D NY South Carolina LWF PIP @ 15ft PIP @ 10ft South Carolina GB PIP @ 5ft Pharr TX Lousiana LWF Crushed Rochester NY El Paso TX Calagary AB Prince George BC Ashdown AR Temple TX Sprain Brook NY Raleigh NC Garden City TX Maple Rd NY Wake Forest NC Round Rock TX Lousiana LWF Uncrushed Waco TX El Paso Coarse MSE San Antonio Bastrop Fine Medium Coarse

Composition, % 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 #10 Mix 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 is Saturate 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-129-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

ASTM G187 (Ω-cm) 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-129-M (Ω-cm) AASHTO T-288 (Ω−cm)

AASHTO T-288 vs. Tex-129-M

BIAS OF RESISTIVTY MEASUREMENTS AS A FUNCTION OF TEXTURE

1 2 3 4 5 6 7

Fine Sand Coarse Sand Gravel

BIAS

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

RESISTIVITY (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

Bias Tex-129-M/AASHTO T-288 d2

#10*nT288*100/(n129-M*(wg*d2 g+wcs*d2 cs+wfs*d2 fs+wf*d2 f))

Fine Sand Coarse Sand Gravel

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” ~ 1:4 Large plastic container with lid TX-620-J Passing #40 1:10 Stirring plate and stirring bar TX-620-M Passing 1 ¾” 1:10 Roller 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 = 0.76 100 200 300 400 500 600 700 800 900 1000 100 200 300 400 500 600 700 800 900 1000

Tex-620-M (mg/kg) 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 10 20 30 40 50 60 70 80 90 100

620-Mcl +0.65*620-MSO4/(0.65*T290+T291) 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

Resistivity (Ω-cm) 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 GC El 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

Resistivity Tex-620-M (Ω-cm) Total Salt Content Tex-620-M (mEq) y = 13488x-0.82

R² = 0.64

100.0 1000.0 10000.0 100000.0 1.00 10.00 100.00

Resistivity AASHTO T-288 (Ω-cm) 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 10.0

NCHRP 21-06 (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

ASTM D 4972 (pH) 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-128-E (pH) 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-620-M (pH) AASHTO T-289 (pH)

COMPARISON of pH MEASURMENTS RELATIVE TO AASHTO T-289

27 2 4 6 8 10 1.03 1.05 1.07 1.10 1.12 More

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

CONCLUSIONS

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

5 10 15 20 25 30 35 40 45

2000 4000 6000 8000 10000 12000 14000 16000 18000 20000

Corrosion Rate (µm/yr) 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

5 10 15 20 25 30 35 40 10000 20000 30000 40000 50000

Measured 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 MULTIVARIATE

• 1. 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) Clay, marly clay, humus

• 2

Peat, thick loam, marshy soil

• 4

Ground water level at buried position None Exist

• 1

Vary

• 2

Resistivity > 10,000 Ω-cm 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 20% or more

• 1

pH 6 or more 6 or less

• 2

Sulfide and Hydrogen Sulfide None Trace

• 2

Exist

• 4

Carbonate 5% or more +2 1% to 5% +1 < 1% Chloride < 100 ppm > 100 ppm

• 1

34

ITEM MEASURED VALUE MARKS Sulfate < 200 ppm 500 ppm – 200 ppm

• 1

1000 ppm – 500 ppm

• 2

> 1000 ppm

• 3

Cinder & Coke None 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 Not Corrosive (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 1.8 3.8 LWF, South Carolina 4.83 68 ASTM WK 24261 1.2 8.4 El Paso Coarse/MSE 0.22 2 Tex-129-M 0.2 NA Waco, TX 1.26 7 Tex-129-M 0.3 NA M-U-D, NY 5.24 82 AASHTO T-288

• 1

4.8 39 Slightly Corrosive

• 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 Corrosive

• 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.