Alternative Deicer Performance Characterization: Know Before the Snow

Summary:

MnDOT has been using alternative deicers (potassium chloride, magnesium chloride, and calcium chloride) to melt roadway ice at temperatures colder than sodium chloride can melt alone. Using alternative deicers in brine form has been a way to leverage treatment techniques at temperatures below 15 degrees F. However, these alternative deicers have not yet had the “phase diagram” or “ice melt capacity relationship” developed to characterize the melting ability (potential and performance) by temperature and deicer concentration. Without these tools, MnDOT operators are working on past observations, hunches and vendor recommendations, without the benefit of the science and education to guide their use of sodium chloride in rock salt brine. In colder regions of the state, the lack of scientific determination can be particularly troublesome as operators make proper decisions to fight refreeze when either temperatures drop or deicer concentrations dilute down, which can result in either unsafe conditions or significantly extra material expense and environmental degradation. This project proposes to develop phase diagram and assess the ice melt capacity of the alternative deicer to be determined early in the project by the Technical Advisory Panel (TAP), specifically: 1. Quantifying the melting curve, eutectic point (lowest temperature melt can be achieved at any concentration), and solubility curve for each of six mixtures at temperatures down to -20 degrees F. 2. Quantifying the ice melting capacity for each of six mixtures at temperatures down to -20 degrees F. 3. Field testing and comparing melt behavior of three mixtures, comparing performance and assessing synergies under actual winter maintenance operations.

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