Salt & Winter Roadway Safety: For Roadway Maintainers (Snowfighters)

Mixing chloride deicing chemicals seems a popular topic. The Salt Institute examined the practice in its Spring 2006 issue of Salt and Highway Deicing (Amsler and Hanneman, "Mixing it up in the fight against winter by blending liquid ice control chemicals") and this week's mail brought the August issue of Roads and Bridges magazine with an article by two APWA Winter Maintenance Subcommittee leaders, Mark Devries (McHenry County, IL) and Bret Hodne (W. Des Moines, IA), entitled "Chloride Cocktail."

Amsler and Hanneman examine the science underlying the experience with using sodium chloride brine mixed with other chemicals. They encourage comparision of melt volume per unit of ice deriving the melting power from the concentration of deicer in molar units. They conclude that adding calcium and magnesium ions will increase the concentration of ions, but the freezing point is lowered only a degree or two and adding CaCl and MgCl increases the risk of precipitation.

Devries and Hodne examine the McHenry County experience with "supermix" -- 85% NaCl brine, 5% CaCl and 10% organic ("De-Ice 55"). The County does not use the liquid at less than 15 degrees F (the normal cutoff for NaCl alone), but as a prewetting agent, they've found it extends the working range of solid deicing salt down to 2 degrees F. As a bonus, they reduced the use of expensive CaCl by nearly 90%.

Cheers!