De-icing Grit - Debunking the Myths
Every winter local authorities and private companies spend long hours on cold nights gritting roads. Their efforts keep the traffic moving in bad conditions and help prevent dangerous ice from forming on the roads. This is because they spread de-icing salt, not a grit.
How does de-icing salt work?
Grit itself does not contain any ingredients that would melt snow or ice. Although it’s called grit, what is used on the roads is actually rock salt (sodium chloride NaC1). Salt contains equal amounts of sodium and chloride and works by lowering the freezing point. When it is added to icy roads is helps to prevent the formation of ice to temperatures as low as – 18 °C. As rock salt dissolves in water the solution will dilute, and in some cases more applications will be required for it to be totally effective. It depends on how cold it is.
The most common type of road salt used on roads is red or brown rock salt. This type of salt gets its colour from where it is mined, and when it is dissolved and diluted it leaves a slight gritty, marlstone residue – hence the reason why it is known as grit.
Some gritting companies may add a bit of sand or gravel to their salt to add more traction on to the road, but by themselves these have no de-icing properties and will not be an effective de-icer.