Rock salt is sodium chloride, the same elements that make up ordinary table salt. Mined from naturally occurring deposits, the salt is processed into large crystals that make them easy to apply on winter ice. Though one of the least expensive materials to use for de-icing, rock salt can degrade the surface of concrete. The salt is also washed off roads and driveways into nearby plantings. High concentrations of salt in the soil are toxic to plants and corrosive to metals. Rock salt is not effective below 15 degrees Fahrenheit, according to Iowa State University horticulturalist Richard Jauron.
Calcium chloride, a compound used for de-icing, comes in the form of small, white pellets and used similar to rock salt. Unfortunately, it can also damage concrete surfaces and harm plant life. Calcium chloride is effective at melting ice below 0 degrees Fahrenheit, according to home improvement expert Tim Carter. It is generally more expensive than rock salt.
Potassium chloride is a de-icer that won't harm nearby plants nor irritate skin like calcium chloride. It is more expensive than rock salt and not effective when temperatures dip below 15 degrees Fahrenheit. Potassium chloride can be mixed with other salts for better melting power.
Magnesium chloride is often used as a safer alternative to rock salt for plants. It continues to melt ice to minus 13 degrees Fahrenheit or below and reacts chemically to a moderate degree with concrete. Magnesium chloride is considered a corrosive compound for metals, however, and should be used with care around utilities and other essential metal products.
Calcium magnesium acetate, or CMA, is used it areas where concrete surfaces must be preserved to a high degree. It has a minimal effect on plant life and the environment and is considerably higher in cost than ordinary rock salt.
Ordinary sand can be used as a safe, nontoxic agent for use on driveways. Though it doesn't melt ice, it provides traction for vehicles without affecting the condition of soil in nearby plant beds. Sand can wash into the environment without harm to neighboring rivers and waterways. While it can be messy when tracked inside home, sand can be mixed with other de-icing chemicals to prevent damage to plants and reduce costs.