Various agencies are researching the use of liquid chlorides for direct applications as a deicer agent in snow removal operations as opposed to use of granular materials. As in most things, there are "pluses and minuses" in both processes. One complaint I consistently hear is the "refreeze" of liquid applications is much quicker than granular. At the risk of being "coined a smart ass"; "DUH". Think about what you are saying for just a minute: "Liquid chlorides are effective as a melting agent as soon as the hit the pavement". Remember: all chlorides work the same: they effectively lower the freezing point, just like the glycol in your car radiator (ethylene or polypropylene). The lowered freezing (euthetic) temperature stays constant as long as the percentage of anti-freeze to water or chloride to water remains consistent. It is at this point that the deicing process and the engine radiator analogy differ. The radiator solution will stay relatively the same unless there is a leak and more coolant has to be added. The liquid chloride solution applied to the road starts diluting as soon as it is applied and initiates the melting process. Once the solution becomes diluted to the point whereby it's freeze protection is higher than the pavement temperature, you get a refreeze. This science remains the same whether you apply straight granular sodium chloride, prewetted granular using sodium, calcium, or magnesium liquid chlorides, or straight liquid chlorides. So why the potential for quicker refreeze when using liquids? Because the liquids go to work much faster in the deicing process. Granular salt does not become an effective deicer until it melts enough snow to form a brine. Until that point, it really isn't doing much for you. If one would record the time from the liquid brine formation when it reaches the same chloride to liquid concentration versus a straight liquid chloride application until there is a refreeze............you would find the time difference to be inconsequential. The huge advantage to a straight liquid application is it provides is a safer driving surface for the motoring public much quicker than the 100% granular applications and it does not "bounce into the ditch". So, what do you do about the refreeze? Couple of things: match your application rate to temperature and amount of snowfall. Warmer temperatures are great for liquid applications. 28 degrees +. If you apply at lower temperatures, raise the application rate to delay any refreeze. If there is a heavy snowfall........you may need a higher application rate for liquid chloride or maybe you should use prewetted granular. Prewetted granular and liquid chlorides both have a place in the snowfighters arsenal. The exception could be very cold areas with huge amounts of snowfall, Upper Peninsula of Michigan being one example, where liquids might not be an option except as prewet agent.
