Evaluation of Test Methods for Characterizing Steel Corrosion Potential in MSE Wall Fill

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Product Number: 51321-16486-SG

Author: Kenneth L. Fishman/ Hamidreza Fakhri/ Soheil Nazarian/ W. Shane Walker/ Arturo Bronson

Publication Date: 2021

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Mechanically stabilized earth (MSE) walls include galvanized steel reinforcements embedded within granular fills to add tensile strength and internal stability to the reinforced soil mass. The potential for corrosion of the steel reinforcements is managed by selecting fills to be noncorrosive, and this requires the implementation of proper techniques for sampling, measurement of electrochemical properties, and characterization of the corrosion potential. This study summarizes the most important findings from NCHRP Project 21-11, “Improved Test Methods and Practices for Characterizing Steel Corrosion Potential of Earthen Materials.”, which aims to assess and improve the current methods for characterizing the steel corrosion potential for MSE wall fills. Although most transportation agencies currently specify AASHTO Standards, including T-288 (resistivity), T-289 (pH), T-290 (sulfate content), and T-291 (chloride content), for evaluating the corrosivity of earthen materials, these standards are limited to materials having a significant component passing a No.10 sieve (e.g., sand and fines), which do not represent typical sizes of MSE wall fills (e.g., coarse gravel or larger). In this study, the veracity of results obtained from these standards is evaluated and compared to data from alternative test methods that accommodate sample domains with a broader range of grain sizes. The test data are evaluated in terms of precision, bias, and how well they correspond to observations of corrosion rates and performance from steel reinforcements that have been embedded in the same fills that were included in the laboratory test program. Based on these comparisons, we recommend protocols for selecting the appropriate program of sampling, testing, and characterizing corrosion potential depending upon the physical characteristics of the materials.

Keywords: corrosion, soil corrosion, MSE wall, galvanized steel, sulphate, chloride, resistivity, pH