All ice-melting compounds are designed to work on the same principle:

When broadcast, each particle of deicer bores a hole through the ice or snow and as it bores it forms a solution.  When the solution reaches the pavement, it spreads out under the ice and snow and breaks the bond between the ice and pavement. This allows the ice to be easily removed by some mechanical devices that are used for that purpose.

The proper use and application of chemical deicers, although a simple process, seems to be associated with a number of misconceptions. The most common ones are listed below:

1.     "Application should be heavy enough to chemically melt all the snow and ice which are present."  This approach is probably the most common cause for tracking problems and damage to trees and shrubs.  As indicated above, only enough ice melter should be applied to bore through and ice and break the bond between the pavement and ice. 

2.     "The heat that is generated by the ice melter is what melts the snow and ice." This is a common misconception, the heat generated is a coincidental property of the compound and is quickly dissipated under normal conditions. In fact, some ice melters such as urea, turn cold when forming a solution and still perform the job of snow and ice melting. 

3.     "The cracking and popping sound is the ice melter breaking up the ice."  The popping sound is only associated with surface expansion.  In fact, surface expansion on concrete is the main source of concrete damage.

It is important to remember before trying to mechanically remove the ice, allow sufficient time for the ice melter to bore through the ice and break the bond between pavement and ice.  At 25° F, it takes about 5-10 minutes to penetrate ¼ inch of ice, plus the time for the solution to spread out under the ice and loosen the ice from the pavement.

Don't be misled by snow and ice melters that appear to work quickly.  These generally consist of smaller particles and under heavy conditions will expend themselves before they bore completely through the ice and snow. A good product will be large enough to melt under extreme conditions yet maintain a moderate rate of melting.