Figure 3-45

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Flowchart for identifying infilling materials in cracks and voids as applied to MN-065-064. This flowchart from Volume 2 of the guidelines shows how to use petrographic or SEM analysis to determine the cause of an MRD. For this site in Minnesota, staining techniques and an SEM analysis were used and the following conditions were found to be present, ultimately helping to establish a cause and effect for each and any possible MRD:

• Sulfates were present; thus, a sulfate attack may have occurred;
• Chloro-aluminates or calcium hydroxide was present suggesting a de-icer attack may have occurred; and
• Neither calcite or magnesium silicate hydrates nor alkali-silica reaction products, iron oxide, or any other substances were present.