Improved Test Methods and Practices for Characterizing Steel Corrosion Potential of Earthen Materials (2020) / Chapter Skim
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18 Chapter 3. Laboratory Measurements (Phase II)
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Florida EL Paso MSE M-U-D NY South Carolina LWF PIP South Carolina GB Pharr TX Beaufort NC Rochester NY El Paso TX Calgary 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 El Paso Coarse MSE Louisiana LWF Crushed Waco TX Bastrop TX TYPE /USCS Sand/SP Sand/SP Sand/SP Expanded Clay/SW Sand/SW Limestone/SW Limestone/SP Limestone/GP Sand/SP Limestone/SW Sand/GW Glacial Till/GW Sandstone/GW Limestone/GW Limestone/GW Granite/GP Limestone/GP Limestone/GW Granite/GP Limestone/GP Limestone/GP expanded clay/SW Limestone/GW Limestone/GP LATITUDE 29°10'44.60"N 31°44'30.5"N 43° 8'12.86"N 33°41'4.49"N 41° 2'16.19"N 33°41'4.49"N 31°56'15.7"N 34°43'37.57"N 43° 6'36.33"N 31°56'15.7"N 50°53'33.50"N 53°38'35.60"N 33°46'18.5"N 31°06'11.0"N 41° 3'44.43"N 35°52'24.89"N 31°51'39.9"N 42°59'28.56"N 35°57'55.56"N 31°47'16.8"N LONGITUDE 82° 8'40.85"W 106°22'26.6"W 75°16'14.39"W 78°57'35.90"W 73°56'58.68"W 78°57'35.90"W 106°32'38.8"W 76°39'51.89"W 77°36'0.36"W 106°32'38.8"W 114° 3'15.88"W 122°39'54.35"W 94°10'54.0"W 97°21'32.2"W 73°48'25.95"W 78°34'6.30"W 101°35'32.2"W 78°47'18.76"W 78°32'30.93"W 106°31'13.6"W LOCATION ON WALL MSE wall is an in-line abutment spanning between two bridge approaches and a median. MSE walls serve as the abutment facing and as a grade separation along the approach.
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20 and expanded clay light weight fill (2)
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21 (a) Sample composition (b)
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22 3.3. Comparison of Results from Different Test Methods We compared results obtained from different test procedures in terms of: (a)
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23 (a) precision (b)
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24 gradation of the sample. We did this to minimize the effects of sample error on the test results such that the variation in results was mostly related to differences among the test procedures.
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26 (b) coefficients of variation (COV = σbias μbias )
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27 We grouped the data from each test method according to the fineness of the samples (fine sand, coarse sand, and gravel) , as previously described in Figure 3-1.
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28 (b) coefficients of variation Figure 3-5 Resistivity measurements from samples with different textures.
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29 Thus, a relatively large difference in results is obtained with Tex-129-M compared to AASHTO T-288 (2016) from materials with these characteristics.
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30 Figure 3-6 Tests for measurements of salt content, and observations of precision (only included results from testing sulfate and chloride with > 10 mg/kg, n=4)
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31 Figure 3-7 Correlation between salt content measurements from Tex-620-M and AASHTO T290 & T-291. We computed bias as the ratio of "equivalent total salt content" obtained from Tex-620-M divided by the "equivalent total salt content" computed from the results of AAAHTO T-290 (2016)
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32 Thus, measurements of resistivity are negatively correlated with the measurements of salt content. We evaluated correlations between salt content and resistivity measurements to assess the veracity of these measurements.
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33 Table 3-3 Resistivity model parameters (ppm of salts)
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34 3.3.3 Measurements of pH We have summarized the statistics describing the precision observed from testing replicates and the bias of each test procedure with respect to AASHTO T-289 (2018) in Figure 3-8.
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35 We draw the following conclusions from the results presented in this section: • Measurements of pH from Tex-620-M are less repeatable compared to measurements from other test methods investigated in this study. • In general, Tex-620-M renders pH values that are higher compared to those obtained from the other test methods investigated in the study.
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37 • When more than 60% of the sample is passing a No.10 sieve, similar results are obtained from measurements of resistivity and salt content via current test standards or the modified Texas procedures (Tex-129-M for resistivity and Tex-620-M for salt contents)
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38 corrosion rates versus measurements of resistivity for plain steel and galvanized elements separately. We obtained the best fit to the data using the power law shown in Equation (3-4)
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39 For Group II, corrosion rates do not correlate as well with corrosion rate measurements compared to the correlations obtained from Group I These correlations can be described as low to moderate (0.19 < R2 < 0.33)
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40 Figure 3-11 Galvanized steel corrosion rates and measurements of resistivity from samples with less than 22% passing the No.10 sieve (via Tex-129-M)
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41 including 10 data points coincident with the samples included in the Phase II laboratory testing for this study (NCHRP 21-11)
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42 observed (Prince George, BC Canada and M-U-D, NY)
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43 • German Gas and Water Works Engineers' Association Standard (DVGW GW9) , which is one of the earliest corrosion assessment methods applied to pipeline construction in Europe (Shreir et al.
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44 Table 3-6 Characterization scheme from DVGW GW9. Item Measured value Marks Soil composition Calcareous, marly limestone, sandy marl, not stratified sand +2 Loam, sandy loam (loam content 75% or less)
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45 Table 3-7 Soil corrosivity/aggressiveness (for carbon steel)
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46 3.4.2.2 Correlation between Results of Characterization Scheme and Performance Data Formulas determined from regression analysis do not depict how corrosion rates vary within selected ranges of resistivity, or other material characteristics. Alternatively, data clusters are useful to quantify the variations and uncertainties associated with data within selected regions of a sample domain.
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47 Table 3-9 Data clustering according to resistivity and observed rates of corrosion. Cluster Sample GN PP#10 Test method (proposed protocol)
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48 Table 3-11 Data clustering relating corrosivity rankingsA to observed rates of corrosion. Cluster Sample GN PP#10 Test method (proposed protocol)
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49 3.5. Recommended Protocol We incorporated recommendations into the proposed protocol (presented in Appendix A)
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new material is received determine the gradation of material GN > 3 or PP#10 > 25% GN < 3 and PP#10 < 25% PP#10 > 15% determine LL, PL, and SE determine electrochemical properties < 15% AASHTO T-288 (ρmin, ρsat)
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