Road salt is what we spread on our roads every year to combat the winter effects of snow and ice which can make our roads unsafe to drive on. It is generally referred to as rock salt in the UK but in order to be clear about the specific operation of clearing snow and ice from our roads we will refer to the product used for this as road salt on this part of our website.
So what is road salt?
Road salt is made up primarily from rock salt, which in effect is the mineral sodium chloride, and which comes from vast underground mines where salt was deposited through the evaporation of seawater that originally covered the UK and Ireland millions of years ago. This evaporation caused huge deposits of salt which were eventually covered over by ground movements. And so it is a chemical sedimentary rock which is used for industrial purposes and is also known as halite.
The salt used in road salt is not like the salt we use on food, it forms in a range of colours but is mostly shades of brown and actually looks like grit.
How does road salt work?
Road salt works essentially by lowering the freezing point of water and moisture on the road which means that instead of freezing at zero degrees centigrade it won’t freeze until between minus six and minus eight degrees. This keeps our roads and motorways free of snow and ice, in most instances, thus making driving and travel safer.
An important point about road salt is that it becomes more effective when cars and other traffic drive over it and provide the dual effect of crushing it into smaller particles and spreading it further over the road.
But unfortunately salt starts to become less effective at around minus five degrees and just about useless at lower temperatures.
The significance of road salt
We spread about two million tonnes of road salt on our roads in the UK each year. Local authorities spread road salt on anywhere from twenty five to thirty percent of their road network which covers mostly motorways and main roads.
Local authorities are responsible for keeping roads clear and safe to drive on in the bad weather and in fact have a legal duty through the Highways Act 1980 to ensure as far as is reasonably practicable the roads are not left unsafe by snow and ice.
The problems with road salt
Road salt pollutes, corrodes and is harmful to wildlife and pets. When the snow and ice melts the salt which is made up of sodium and chloride doesn’t just disappear.
So what happens is that the salt becomes part of the melted snow and ice and washes into groundwater, streams and other water sources. To put the potential pollution in perspective five gallons of water will be permanently polluted by just a single teaspoon of salt and once there cannot be removed.
The salt causes damage to plant life and vegetation and also harms fish.
The corrosive nature of chloride based chemicals is well known and rock salt causes corrosion in vehicles and can heighten degradation of concrete and steel structures.
The combination of corrosive and toxic properties is also dangerous to small animals and pets which may come into contact with the road salt. Reported problems include irritation to paws, and if ingested, seizures and toxic poisoning.
So minimising the use of road salt or using alternatives and stopping it altogether will improve the environment and safeguard the health of small animals and pets. A worthy objective indeed.