Electrochemical Test Methods to Evaluate the Corrosion Potential of Earthen Materials (2021) / Chapter Skim
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17 This chapter describes the sampling and testing program implemented during Phase II. The research team used data from the laboratory test program to study the precision and bias of measurements from different test procedures.
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18 Electrochemical Test Methods to Evaluate the Corrosion Potential of Earthen Materials North Carolina (n = 3) , South Carolina (n = 2)
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Laboratory Measurements 19 Characteristic Site (sample type/USCS designation) South Carolina LWF (expanded clay/SW)
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20 Electrochemical Test Methods to Evaluate the Corrosion Potential of Earthen Materials Characteristic Site (sample type/USCS designation) El Paso, TX (limestone/SW)
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Laboratory Measurements 21 Characteristic Site (sample type/USCS designation) Maple Rd., NY (limestone/GW)
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22 Electrochemical Test Methods to Evaluate the Corrosion Potential of Earthen Materials Fi ne M ed iu m 0 20 40 60 80 10 0 egatnecreP Fines Fine Sand Coarse Sand Gravel C oa rs e Florida El Paso, TX, MSE M-U-D, NY South Carolina LWF PIP, NY @ 15ft PIP, NY @ 10ft South Carolina GB PIP, NY @ 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, TX, Coarse MSE San Antonio, TX Bastrop, TX (a) Figure 3-1.
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Laboratory Measurements 23 0 1 2 3 4 5 6 Fi ne M ed iu m C oa rs e Grading Number (GN) Florida El Paso, TX, MSE M-U-D, NY South Carolina LWF PIP, NY @ 15ft PIP, NY @ 10ft South Carolina GB PIP, NY @ 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, TX, Coarse MSE San Antonio, TX Bastrop, TX (b)
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24 Electrochemical Test Methods to Evaluate the Corrosion Potential of Earthen Materials 0 10 20 30 40 50 60 70 80 90 10 0 Fi ne M ed iu m C oa rs e Percentage passing #10 sieve Florida El Paso, TX, MSE M-U-D, NY South Carolina LWF PIP, NY @ 15ft PIP, NY @ 10ft South Carolina GB PIP, NY @ 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, TX, Coarse MSE San Antonio, TX Bastrop, TX (c) Figure 3-1.
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Laboratory Measurements 25 The percentage passing the No. 10 sieve (2 mm)
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26 Electrochemical Test Methods to Evaluate the Corrosion Potential of Earthen Materials The process for determining the resistivity from a soil box test is described in Section 1.3.3 (see Figure 1-1)
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Laboratory Measurements 27 Details about the precision and bias of the test results obtained from different test procedures are discussed in the following subsections. 3.3.1.1 Precision/Repeatability for Individual Test Methods Three to five replicates from nine different samples were tested with each test method.
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28 Electrochemical Test Methods to Evaluate the Corrosion Potential of Earthen Materials obtained from AASHTO T 288 (Figure 3-3, a and b as compared with the resistivity measurements obtained with Tex-129-M and ASTM WK24621 (Figure 3-3, c and d)
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Laboratory Measurements 29 • The mean bias is greater for test procedures that involve coarser gradations (i.e., ASTM G187, Tex-129-M, and ASTM WK24621)
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30 Electrochemical Test Methods to Evaluate the Corrosion Potential of Earthen Materials The data from each test method were grouped according to the fineness of the samples (fine sand, coarse sand, and gravel) , as previously illustrated in Figure 3-1.
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Laboratory Measurements 31 sample. This is because the sample is separated on a No.
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32 Electrochemical Test Methods to Evaluate the Corrosion Potential of Earthen Materials ASTM D4327 was employed to measure chloride and sulfate concentrations simultaneously as well as other anions (e.g., bicarbonate anion) by using the ion exchange chromatograph.
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Laboratory Measurements 33 The research team tested 26 samples: 21 according to AASHTO and Texas modified procedures and five according to Tex-620-M only. The five coarse samples were not tested according to the AASHTO standards because of the lack of sufficient constituents passing the No.
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34 Electrochemical Test Methods to Evaluate the Corrosion Potential of Earthen Materials • For samples with more than 60% of the particles passing the No. 10 sieve, the bias was close to 1.
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Laboratory Measurements 35 measurements observed on compacted soil specimens was obtained with the AASHTO test series (R2 = 0.64) and the worst with ASTM WK24621 and Tex-620-M (R2 = 0.36)
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36 Electrochemical Test Methods to Evaluate the Corrosion Potential of Earthen Materials • The best correlation between salt content and resistivity measured on a compacted specimen is obtained with the AASHTO test standards. • Milliequivalents are the best way to express salt content and to allow consideration of the effects from other salts besides chloride and sulfate on the resistivity measurements.
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Laboratory Measurements 37 The bar graphs and whiskers in Figure 3-8 represent the mean and standard deviation, respectively, in pH units. The pH measurements from all samples range between 7.6 and 9.5.
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38 Electrochemical Test Methods to Evaluate the Corrosion Potential of Earthen Materials alternative to AASHTO T 288 for testing coarse materials. The following observations were made on the basis of the distribution of bias in the results: • When more than 60% of the sample passes the No.
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Laboratory Measurements 39 terms of the durability of earth reinforcements as quantified by observations of metal losses and corrosion rates (CRs)
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40 Electrochemical Test Methods to Evaluate the Corrosion Potential of Earthen Materials CR m year cm (3-4)
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Laboratory Measurements 41 MSE wall in El Paso, Texas. The correlation corresponding to AASHTO T 288 and Tex-129-M is shown in Figure 3-10 and Figure 3-11, respectively.
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42 Electrochemical Test Methods to Evaluate the Corrosion Potential of Earthen Materials Figure 3-11 depicts data from application of Tex-129-M to samples with less than 22% of particles passing the No. 10 sieve.
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Laboratory Measurements 43 3.4.1.2 Performance of Plain Steel The correlation between test results from Group I and corrosion rates measured on plain steel specimens was considered to be low (0.08 < R2 < 0.20)
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44 Electrochemical Test Methods to Evaluate the Corrosion Potential of Earthen Materials approach. Several schemes exist for screening and characterizing the corrosion potential of earthen materials.
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Item and 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)
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46 Electrochemical Test Methods to Evaluate the Corrosion Potential of Earthen Materials The characterization of corrosivity was compared with the measurement of the corrosion rate from galvanized and plain steel elements. The following sections compare correlation with performance considering the characterization of corrosivity by DVGW GW 9.
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Laboratory Measurements 47 Sample GN PP#10 Test Method (proposed protocol)
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48 Electrochemical Test Methods to Evaluate the Corrosion Potential of Earthen Materials 3.5 Recommended Protocol Recommendations based on the results of the analyses of the data collected in Phase II of this study were incorporated into the proposed protocol (see appendix) , which is shown as a flowchart in Figure 3-14.
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Note: Cl– = chloride; SO4 = sulfate; H2O = water; CaCO3 = calcium carbonate. Figure 3-14.
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50 Electrochemical Test Methods to Evaluate the Corrosion Potential of Earthen Materials Four factors were considered in selecting methods for the proposed protocol: • Precision and repeatability of the test methods, • Compatibility between parameters (e.g., salt content and resistivity) , • Correlation between geochemical and electrochemical properties -- corrosivity and corrosion rates, and • Utility of the test results.
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