The science behind treating the roads for ice and snow

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Icy road conditions made for a slippery and dangerous commute throughout the Twin Cities metro on Monday.

Minnesota Department of Transportation crews stayed busy working to de-ice the roads.  

“There are different ways of treating different roadways with different chemicals,” said Lloyd Law with MnDOT.

Law specializes in clearing metro area roads of snow and ice. He says that depending on the temperature, salt is typically what crews turn to first.

“The general rule of thumb is sodium chloride salt, that’s just regular white rock salt, is effective to about 15 degrees and it varies from pavement temps to air temps,” said Law.

The next line of defense is a calcium or magnesium chloride product, which unlike salt, takes moisture out of the air and can work when temperatures fall below zero. Law says that the automatic deicing chemicals used on bridges is different than what is used on the roadways.

“Now your air temps can be higher, your pavement temps can be lower and vice versa so what we watch, is we watch pavement temps,” he said. “And we’ll adjust our chemicals to what the pavement temps are.”

From salt to chloride to blends of sugar, the science to treating winter roads continues to evolve.  

“We’re constantly trying new blends, new chemicals,” said Law.