Frequently Asked Questions
Cement & Concrete
Technology Home > FAQs > Deicers.
 Q:
What effects do deicers have on concrete?
A: Sodium chloride:
Sodium chloride has little or no effect on properly air entrained
concrete but will damage plants and corrode metal.
Calcium chloride: Calcium chloride in weak solutions
has little chemical effect on concrete or vegetation but does corrode
metal, and strong calcium chloride solutions can chemically attack
concrete. The reaction is accelerated by high temperature
Magnesium chloride:
A PCA literature search found three references comparing the effects
of magnesium chloride with sodium chloride and other deicers on
the scaling resistance of concrete. Unfortunately, the cited studies
provide conflicting results.
The abstract from a German field study (Leiser 1967) states that
"concrete surfaces were only slightly affected [by magnesium
chloride lye], and that the solution is less harmful than granulated
salt." However, two recent studies found magnesium chloride
to be more aggressive than sodium chloride.
In the first study (Cody 1996), concrete containing dolomite coarse
aggregate was cored from five highway pavements. Small blocks were
cut from the cores and subjected to wet-dry and freeze-thaw cycles
in 0.75M and 3.0M solutions of NaCl, CaCl2, and MgCl2. Magnesium
chloride was the most destructive deicer, producing severe deterioration
under almost all of the experimental conditions. Calcium chloride
was the next most destructive salt. Sodium chloride was relatively
benign. In the second study (Lee 2000),
the researchers again found magnesium chloride to be significantly
more aggressive than sodium chloride in wet-dry and freeze-thaw
conditions.
In both of these studies, the
authors concluded that the major cause of deterioration by magnesium-based
deicers was the formation of non-cohesive magnesium silicate hydrates
(MSH), produced by the reaction of dissolved magnesium with calcium
silicate hydrates of the cement. Because MSH does not form strong
bonds with aggregate particles, these phases cause loss of cohesion
in portland cement paste and will promote crumbling. A common finding
of the above research is that all deicers can aggravate scaling,
emphasizing the need for placing high-quality, air-entrained concrete
in deicer environments.
Urea does not chemically damage
concrete, vegetation or metal.
Ammonium: Deicers containing ammonium
nitrate and ammonium sulfate should be prohibited because they rapidly
attack and disintegrate concrete. Deicers used in low concentrations
(2% to 4% by weight) can cause more surface scaling than higher
concentrations or no deicer at all.
For more information about deicers read Winter
Weather, Deicers Need not Damage Concrete.
References:
Cody, R.D., Cody, A.M., Spry, P.G., and Gan, G., "Experimental
Deterioration of Highway Concrete by Chloride Deicing Salts,"
Environmental & Engineering Geoscience, Vol. II, No.
4, Winter 1996, pp. 575–588.
Lee, H., Cody, R.D., Cody, A.M., and Spry, P.G., “Effects of Various
Deicing Chemicals on Pavement Concrete Deterioration,” Proceedings
of the Mid-Continent Transportation Symposium, Center for
Transportation Research and Education, Iowa State University, 2000.
Leiser, K., and Dombrowski, G., "Research Work on Magnesium
Chloride Solution Used in Winter Service on Roads," Strasse,
Vol. 7, No. 5, Berlin, Germany,
May 1967.
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