Regular rock salt is ineffective below 18 degrees Fahrenheit. This is a 53-degree net gain in working temperature.
Calcium Chloride works through a chemical reaction that creates a short burst of extreme heat to start the melting solution. The heat is generated for 7-11 minutes then stops. However, it must be shoveled away to prevent refreeze. Otherwise, black ice & slippery conditions will occur. Also, recurring freeze/thaw cycles will prematurely age concrete.