Rock salt, or sodium chloride, is one of the least expensive methods of melting ice. Rock salt raises the freezing temperature of water, causing it to melt at lower temperatures. It works fairly well, but rock salt can be caustic, eroding metal fence posts, light posts or lawn ornaments. Rock salt can also pit concrete and damage landscaping.
Like rock salt, chemical de-icers also work by lowering the freezing point of water to a temperature that's lower than the outside air temp. Chemical de-icers are usually composed of some sort of salt, primarily either calcium chloride or magnesium sodium.
When reporter Kelly Gunderson of Station KRCG in New Bloomfield, Missouri compared a number of different ice melting solutions, she found that calcium chloride was the most effective, melting the ice fastest and most completely. It was also the most expensive method she tested. Magnesium sodium was slightly less effective.
When purchasing chemical de-icers, look for the highest concentration of the active ingredient to other ingredients. Cheaper formulas have less of the active ingredient and you'll have to use more product to get good results. More expensive formulas can be more cost-effective in the long run because you can use less of the product at a time.
Chemical de-icers can be harmful to pets, burning their feet if they walk on them, an poisoning them or at least upsetting their stomachs if they ingest any of the granules. Run-off from melted de-icers can also contaminate streams, so use these products sparingly.
While rock salt and chemical de-icers work to physically melt the ice, other methods such as sand, cinders or kitty litter use the heat of the sun to melt the ice. The darker colors of these substances absorb sunlight, but they don't work when the sun isn't out. They can provide traction on slippery substances, and they don't harm the environment or surrounding vegetation, concrete or metal. They're also inexpensive.
These methods work more slowly than rock salt or chemicals, and they can be messy. If you use these methods, be careful not to track them into the house.
The most cost-effective method of melting ice may be to combine an expensive solution such as a calcium chloride chemical de-icer with a less expensive method such as sand or rock salt. The cheaper ingredient adds a little boost of its own and helps the expensive ingredient go further. This is a method used by many state or city road crews; they mix sand with a chemical de-icer or salt and spread it on roads to keep them ice free.