Improved Test Methods and Practices for Characterizing Steel Corrosion Potential of Earthen Materials (2020) / Chapter Skim
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51 Chapter 4. Field Measurements (Phase III)
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52 Table 4-1 Laboratory tests performed on the site and source samples. Samples Site Source Owners (state DOTs)
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53 (a) San Antonio, TX (b)
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54 In Figure 4-2, we present the gradation curves for the different materials sampled from the sites cited in this chapter. In Table 4-2, we summarize salient details of each sample in terms of aggregate size, grading number, and USCS classification to describe the characteristics of the sample domain used in the field and laboratory tests.
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55 4.3. Results 4.3.1 Resistivity β Soil Boxes In Figure 4-3, we show the laboratory measurement of soil resistivity using the modified soil box for the samples retrieved from the sources and the sites included in Phase III.
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56 (b) Test setup Figure 4-3 Resistivity measurement using modified soil box (DAQ = data acquisition system)
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57 4.3.2 Resistivity β Field Tests using Wenner Technique We performed in-situ resistivity measurements at each site using the Wenner 4-probe technique, as described by ASTM G-57 (2012) and Wenner (1915)
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58 (b) Test setup in the field Figure 4-5 The Wenner 4-probe technique.
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60 ππ = 4πππππΆπΆ 1 + 2ππ βππ2 + 4ππ2 β 2ππ β4ππ2 + 4ππ2 (4-1) When the penetration depth of the probes is small in comparison to the spacing among them (b < 0.05 a)
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61 e) Buffalo, NY β parallel to pavement f)
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62 observation may be related to the significantly higher effect of the reinforcements in reducing the resistivity at 0.5 feet depth compared to that at 2.0 feet depth (i.e., having one layer of reinforcement in a 0.5-feet thick material has a more significant charge carrying effect compared to that over a thickness of 2.0)
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63 Figure 4-9 Extrapolating the moisture-resistivity curves to determine the resistivity at in-situ moisture content for the site in Buffalo, NY. Table 4-3 In-situ (Wenner 4-probe)
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64 Figure 4-4. Considering the AASHTO requirements for fills in MSE walls (presented in Table 1)
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65 Figure 4-11 Comparison of sulfate content results obtained from samples collected from the sites and sources.
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66 5. A bottle roller is not standard equipment for a geotechnical lab and other methods of mixing should be implemented for measuring salt contents and pH in accordance with Tex-620-M.
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67 variations between samples when we implemented the laboratory test program for Phase II, which mitigated the sampling error. β’ Reinforcements affect the in-situ measurements of resistivity from MSE wall fills.
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