Rock salt has been a staple in the ice-melting industry for a long time and is still very popular for use at home and by public utilities. Many other types of ice-melting products composed of various chemicals have been introduced over the years. According to peterchemical.com, more than 100 different brands of ice-melting products are currently on the market. Some work better at lower temperatures than others, and you might want to consider using these products when the temperature nears zero.
Potassium chloride, rock salt, magnesium chloride and calcium chloride are the most common ice-melting salts used today. Ice melters are not naturally hot; they do not melt ice as the term suggests, but rather, they act to depress or lower the freezing point of the snow or ice they are spread on. This allows the salt or chemical particles to bore their way through ice and form a layer of brine under the surface, which helps the top layer of ice break up. If the brine is able to remain in place, it will continue to melt any snow or ice that comes in contact with it.
Some salts are more effective than others as temperatures drop. Calcium chloride, one of the more expensive products--around $20 for 50 pounds, works well in temperatures as low as -25 degrees Fahrenheit. Magnesium chloride, calcium magnesium acetate and sodium acetate all work well as long as temperatures are above 5 degrees. Potassium chloride and urea, a pure nitrogen fertilizer, follow at 12 and 15 degrees respectively. Sodium chloride--rock salt--is least effective and will not melt ice when temperatures are below 20 degrees Fahrenheit.
Other considerations when choosing an ice-melting product are how fast it will work and how long it will last before reapplication is needed. Calcium chloride and magnesium chloride will melt faster and last longer than sodium chloride and potassium chloride, according to peterschemical.com. This is because they do not evaporate as quickly as other products.
Some ice melters are hard on concrete, such as ammonium sulfate and ammonium nitrate. Other ice melters can cause spalling, or the breaking up of concrete, due the constant freezing and thawing associated with multiple applications over a winter season. Peterschemical.com recommends removing slush and excess salt from the concrete after you have successfully removed the snow and ice.
If you are worried about salt damaging plants or bushes near your driveway or sidewalk, try using urea, which is a nitrogen-based fertilizer. You may not experience the same salt-melting results that are achieved with calcium chloride, but you will get an added bonus of vibrant green grass after the spring thaw.