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12/2/2008 12:00:00 AM
Compiled by FacilitiesNet Staff
Historically, grounds care departments have removed snow and ice by
overusing chemicals to complement the use of shovels, plows, and
related equipment. In recent years, granular materials have become a
popular and effective method for maintaining safe conditions during and
after a storm.
Understanding the difference between anti-icing and deicing can give
managers insights into the different approaches that can help them deal
with ice efficiently.
Deicing is the reactive application of industrial snow melter to
eliminate existing snow and ice on driving or walking surfaces. Deicing
after snow removal operations can melt any remaining snow and ice.
Anti-icing refers to the proactive application of industrial snow
melter to driving or walking surfaces before a storm. This tactic helps
prevent snow and ice from bonding to the pavement, and workers can
clear them away more easily. Used effectively, anti-icing can create
some of the safest conditions in the winter and can be a cost-effective
alternative to deicing.
Common industrial snow melter products include:
Sand. Although sand can provide some traction, it technically is
not a deicing material, since it does not melt snow or ice. A common
misconception is sand is the best alternative for snow and ice control,
due to its low cost and common use. Managers also need to consider the
potential environmental impact of sand.
Salt. Sodium chloride (NaCl), or rock salt, is a well-known
industrial snow melter. This product generally is effective, though not
in all conditions. In very cold conditions — typically below 23 degrees
— salt begins to lose its effectiveness and either is not used or is
overused in trying to make up for reduced performance.
Sand-salt mix. Another common practice is to mix sand and salt
for deicing. This method is effective in maintaining some traction, due
to the sand. But it reduces the amount of salt workers can apply to an
area. As a result, less deicing occurs, while the environmental
concerns and clean-up costs associated with sand rise.
Beyond Salt and Sand
Managers have other industrial snow melter options for deicing and
anti-icing, and each offers differing levels of effectiveness, cost,
availability, and environmental impact. These products include calcium
chloride (CaCl), magnesium chloride, potassium chloride, urea, calcium
magnesium acetate, and potassium acetate.
CaCl is effective as an industrial snow melter down to about minus-20
degrees. It is an exothermic salt, meaning it releases heat as it melts
the ice. It melts ice faster than other common deicers, but it tends to
attract moisture from the air even after melting the ice, causing
pavements to remain moist. If the moisture refreezes, it creates icy
conditions, and the ice expansion can cause surface damage. Wet-dry and
freeze-thaw cycles lead to spalling, which means flaking or chipping.
CaCl also can be more corrosive to metals, and it can cost more than
Magnesium chloride has many similarities to CaCl, including cost. It is
exothermic and absorbs moisture from the air. This characteristic makes
it a fast-acting industrial snow melter when applied as a solid and
mixed with sand or salt. Crews also can spread it directly on pavement
as a liquid before a storm arrives. In temperatures ranging from 15- to
minus-20 degrees, it is more effective than NaCl but less effective
Many people believe potassium chloride and urea are safe products to
use around vegetation, but this is a common misconception. Fertilizer
is good for plants, but at high concentrations, it can be deadly. Urea
does not contain chlorides, so it is less corrosive and safer for use
on concrete containing rebar and around steel structures. Urea is
effective to 15 degrees and potassium chloride to 12 degrees. Both
materials work more slowly than calcium chloride.