NCHRP 21-11 Update Improved Test Methods & Practices for Characterizing Steel Corrosion Potential of Earthen Materials 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 2019 Midwest Geotechnical Engineering Conference Crown Plaza Columbus, Ohio September 18, 2019 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
Composition, % 100% 20% 40% 60% 80% 0% Florida Fine EL Paso MSE M-U-D NY South Carolina LWF PIP @ 15ft Gravel PIP @ 10ft Material Composition Medium South Carolina GB PIP @ 5ft Pharr TX Lousiana LWF Crushed Coarse Sand Rochester NY Material Source El Paso TX Calagary AB Prince George BC Ashdown AR Temple TX Sprain Brook NY Fine Sand Raleigh NC Garden City TX Coarse Maple Rd NY Wake Forest NC Round Rock TX Lousiana LWF Uncrushed Fines Waco TX El Paso Coarse MSE San Antonio Bastrop 7
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 Mix with 150 ml, let AASHTO T288 (Standard) Passing #10 Small stand for 12 hrs. As is, remove ASTM G187 particles greater Start as is Small than ¼” Small medium, or large Saturate and wait ASTM WK 2461 (depending on maximum As is 24 hrs. aggregate size) TX-129-E (Small Box Method) Passing #8 Start dry Small Small medium, or large TX-129-M (Big Box Method) As is Start dry (depending on maximum aggregate size)
RESISTIVITY TESTS TEST STANDARD SEPARATION MOISTURE CURE PERIOD BIAS w.r.t. PRECISION µ COV (%) CONDITIONS AASHTO T-288 12 hours for 1 st AASHTO T-288 #10 increments - 4.6 increment TEX-129-E #8 increments None 1.07 3.2 ASTM G-187 ¼ inch As-is or None 1.41 5.3 saturated TEX-129-M none increments, but saturated for None 2.28 4.8 coarse materials ASTM WK24621 none Drained from a Soak for 24 3.75 7.4 saturated hours before condition draining 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 4.6 9.1 6.1 Repeatability Coefficient of Variation, COV, % 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
AASHTO T-288 vs. Tex-129-E 20000.0 Tex-129-E ( Ω -cm) 15000.0 y = 0.9614x 10000.0 R² = 0.9543 AASHTO T-288 vs. Tex-129-M 5000.0 40000.0 Tex-129-M ( Ω -cm) 35000.0 0.0 0.0 5000.0 10000.0 15000.0 20000.0 30000.0 AASHTO T-288 ( Ω− cm) 25000.0 20000.0 15000.0 AASHTO T-288 vs. ASTM G 187 10000.0 ASTM G187 ( Ω -cm) 5000.0 20000.0 y = 1.1484x 0.0 0.0 10000.0 20000.0 30000.0 40000.0 15000.0 R² = 0.8835 AASHTO T-288 ( Ω− cm) 10000.0 5000.0 0.0 0.0 5000.0 10000.0 15000.0 20000.0 AASHTO T-288 ( Ω− cm) 12
BIAS OF RESISTIVTY MEASUREMENTS AS A FUNCTION OF TEXTURE 7 6 5 4 BIAS 3 2 1 0 Fine Sand Coarse Sand Gravel MATERIALS Tex-129-E ASTM G187 Tex-129-M ASTM WK24621 13
Effect of Texture on Resistivity 50000.0 Florida EL Paso MSE 45000.0 M-U-D NY South Carolina LWF 40000.0 PIP @ 15ft PIP @ 10ft 35000.0 RESISTIVITY (Ω-cm) South Carolina GB PIP @ 5' 30000.0 Pharr TX Rochester NY 25000.0 El Paso TX Calagary AB 20000.0 Raleigh NC Prince George BC 15000.0 Temple TX Sprain Brook NY 10000.0 Maple Rd NY Wake Forest NC 5000.0 Round Rock TX El Paso Coarse MSE 0.0 AASHTO T-288 Tex-129E G-187 Tex-129M ASTM WK-2461 TEST METHOD 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.
TRENDING OF BIAS FROM TEX-129-M 9.00 8.00 Bias Tex-129-M/AASHTO T-288 7.00 Fine Sand 6.00 Coarse Sand 5.00 Gravel 4.00 3.00 2.00 1.00 0.00 0.001 0.010 0.100 1.000 d 2 #10 *n T288 *100/(n 129-M *(w g *d 2 g +w cs *d 2 cs +w fs *d 2 fs +w f *d 2 f )) 15
GN &PP #10 CORRESPONDING TO BIAS TRENDS Sample Bias < 1.5 1.5 < Bias < 3.0 Bias > 3 Types GN PP #10 GN PP #10 GN PP #10 Gravel - - 1.99 – 3.00 6- 40 3.00 – 3.56 24 - 40 Coarse 4.48- 4.83 60 - 70 3.85 - 4.48 50 - 60 - - Sand Fine Sand 5.00 - 6.65 > 80 - - - - 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% 16
Tests on Leachate Test Aggregate Size Soil to Water Ratio Set up Large plastic SCDOT T143 Passing 1 ½” ~ 1:4 container with lid Stirring plate and TX-620-J Passing #40 1:10 stirring bar Roller and 2-Liter TX-620-M Passing 1 ¾” 1:10 plastic bottle
MEASUREMENTS OF SULFATE CONTENT TEST SEPARATION DILUTION HEATED MIXING FILTRATION PRECISION µ COV (%) STANDARD RATIO AASHTO T-290 #10 1:3 NO SHAKEN CENTRIFUGE 10.1 & FILTER STIR EVERY 140 ° F TEX-620-J #40 1:10 HOUR FOR 12 FILTERED 11.8 HOURS TEX-620-M NONE 1:10 NO MIXED FOR FILTERED 10.7 60 MINUTES 18
MEASUREMENTS OF CHLORIDE CONTENT TEST SEPARATION DILUTION HEATED MIXING FILTRATION PRECISION µ COV (%) STANDARD RATIO SHAKE AASHTO T-291 #10 1:3 NO FOR 20 SEC, CENTRIFUGE 7.5 STAND FOR 1 & FILTER HOUR, SHAKE STIR EVERY 140 ° F TEX-620-J #40 1:10 HOUR FOR 12 FILTERED 3.7 HOURS TEX-620-M NONE 1:10 NO MIXED FOR FILTERED 12.9 60 MINUTES 19
CORRELATIONS BETWEEN SALT CONTENT MEASURMENTS 1000 Sulfate 900 Chloride 800 Linear (Sulfate) Tex-620-M (mg/kg) 700 Linear (Chloride) 600 500 400 620-M (mg/kg) = 0.71(T-290) R² = 0.79 300 200 620-M (mg/kg) = 0.51(T-291) R² = 0.76 100 0 0 100 200 300 400 500 600 700 800 900 1000 AASHTO T-290 & 291 (mg/kg) 20
CORRELATION BETWEEN BIAS FROM SALT CONTENT MEASUREMENTS AND PP #10 1.40 620-M cl +0.65*620-M SO4 /(0.65*T290+T291) >60% CONCLUSIONS 1.20 1. PP #10 < 25% 1.00 = lowest bias 0.80 Bias = 0.06(PP #10 ) 0.64 2. PP #10 > 60% R² = 0.76 = bias > 1 0.60 0.40 0.20 <25% 0.00 0 10 20 30 40 50 60 70 80 90 100 PP #10 (%) 21
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
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