Calcium chloride or magnesium chloride are the most effective moisture attractants. Sodium chloride, or common salt, is cheaper but not very effective alone. It can be mixed with the calcium chloride in equal parts to reduce the cost, however. Calcium chloride is the same material commonly used for fluid ballast in farm tractor tires and is readily available in a flake or pellet form. Calcium chloride should be mixed into a solution and sprayed on the surface at a rate of 1 to 1.5 pounds of salt per square yard.
Magnesium chloride is a by-product of potash production and is available as a liquid solution.
This complicates transport and storage, and generally requires ordering a tanker truckload. It should be applied at a rate of 0.5 gallon of 30 percent solution per square yard. Thirty-seven gallons of this product would treat the same amount of road surface as in the example above. Again, a follow-up treatment at half the original rate is often needed. The applied cost of calcium or magnesium chloride is typically between 30 cents and 50 cents per running foot of road.