Last time, we discussed that there are alternatives to using salt as a deicer. Today we will discuss the specifics of liquid deicers. The purpose of a deicer is to break the bond between snow or ice and the pavement. This process is different from using salt because salt works from the top down. It lands on top and breaks down the snow and ice until it gets to the pavement. Liquid deicers work from the bottom up. They penetrate downward until they reach the pavement. They then spread outward to undercut and break the bond. This allows the hard-packed ice and snow to be easily removed by mechanical means such as plows. It should be noted that liquid deicers are not necessarily intended to clear every bit of ice and snow on the road.
The strategy in which liquid deicers are applied is affected by the geography. In the Midwest, where black ice and ice storms are more common, an anti-icing strategy can be effective. Crews spread liquid deicers ahead of the storm, and the chemicals prevent the bond between ice and pavement from forming. In the upper Midwest, where snows are much heavier, liquid deicing chemicals are used to aid traditional plowing techniques. The purpose of the deicing chemicals here is to reduce, not necessarily break, the bond between ice and pavement to help make plowing easier. They are also used to pre-wet the salt to increase the effectiveness of granular salts.
However, every situation does not call for the use of liquid deicers, and the way in which they are applied varies with the type and amount of precipitation forecasted as well as the pavement temperature, air temperature, humidity, and dew point. Click on the following link to read more about deicing strategies: Public Works Online.