Figure 3-20: Flowchart.

Flowchart for identifying infilling materials in cracks and voids as applied to the Spearfish, South Dakota site. This flowchart from Volume 2 of the guidelines shows how to use petrographic or SEM analysis to determine the cause of an MRD. For the Spearfish, South Dakota site, staining techniques and both scanning electron and petrographic microscope analysis were used and the following conditions were found to be present, which led to the establishment of a cause and effect for each MRD:

• Sulfates were present suggesting a sulfate attack may have occurred;
• Chloro-aluminates or calcium hydroxide were present suggesting a de-icer attack may have occurred;
• Calcite or magnesium silicate hydrates were not present;
• Alkali-silica reaction products were present; thus, a possible ASR may have occurred; and
• No iron oxide or other substances were present.
  

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