Two misconceptions – grit is actually rock salt. Grit is not an effective way to deal with snow. But read on to find out more about the origins of rock salt and GRITIT's use of marine salt to effectively keep premises safe over winter.
Brown Salt and Marine Salt and How it All Began
Grit used by many councils to melt ice and add traction is principally rock salt. Rock salt is extracted from mines in the UK that was ‘made’ 200–300 million years ago, when much of Britain was covered by a shallow sea surrounded by hot dry desert lands. As the water from this sea evaporated, salt crystals formed from the brine, along with other minerals such as gypsum (used for wall plaster) and potash (used for fertiliser).These desert sands are what gives rock salt its pinkish colour.
The good thing about rock salt is it is a coarse-grained siliceous rock, usually with sharp, angular grains. (Siliceous rocks are sedimentary rocks that have silica (SiO2) as the principal constituent), when dissolved it provides a high salt content that reduces the freezing point of water. Rock salt mined from places such as North Yorkshire is produced as a by-product of potash operation. The extraction process leaves insoluble impurities in this salt but can be good for adding some traction on the surface. Many local councils now use 6mm grains of rock salt, reducing the risk of any potential damage to vehicle windscreens.
But the downside is when it is used in commercial settings regularly the impurities wash into drains and causes blockages. Much like the old –fashioned grit that added sand to salt and grit and often left behind a sticky residue, potentially creating somewhat slippery driving conditions and blocking the drains, this is not the environment that we want on our roads today!
Why It’s a No No for Sand for Dealing with Ice and Snow
Sand may be low cost but will not melt ice. It can build up, damage vegetation and block drains, and requires regular sweeping. Used for decades as a temporary friction layer it is found to be more detrimental than chemicals. A Wisconsin study found that at highway speeds sand is swept off the road after eight to 12 cars roll over it. And just to cover the roads, you have to dump a lot of sand. A truck loaded with salt can cover 22.5 miles of two-lane highway. To do that same stretch with sand requires seven loads.
The Pros and Cons of Gritting Salt
The larger problem with rock salt though, is that it stains surfaces and easily brought in by foot to damage carpets and leave unsightly residues on hard surfaces. Secondly, while there are reserves of rock salt in the UK to last hundreds of years, mainly in Cheshire and County Antrim, it is not a renewable resource and has to be mined out of the grounds.
GRITIT does not use rock salt. Marine salt is a more effective agent than rock salt as there are impurities. We use pure sea salt instead which is 99% Sodium Chloride which provides a very high salt content when dissolved into the saline solution on the ground. This is pure white so it prevents staining and residue, but more importantly for the environment, it is a renewable resource
Pure salt is the most effective pre-treatment. Salt has to work twice as hard if it is applied to ice to melt it than prevent it forming in the first place. Applied pro-actively it helps to prevent snow and ice bonding to the pavement, making it easier to clear away. Detailed weather predictions aid proactive application of salt to create some of the safest conditions and a cost-effective alternative to de-icing.
Gritted roads are still not able to hold up against overnight heavy snowfall, which will still settle even in the presence of salt. Therefore we only clear snow once the snow has stopped and then spread grit to ensure that melted snow will not freeze to ice.
In adverse conditions Grit is often added once snow has started to lay and compact and some councils, especially in colder areas, may still prefer to use 10mm grains of rock salt, which can provide a better coverage on wider roads, such as motorways or dual carriageways.
In Brief - Benefits of Brown and White Salt
- Brown de-icing salt tends to be drier than white salt and spreads more easily, but with the right spreading equipment there is very little difference
- Brown de-icing salt is marginally cheaper to buy than white de-icing salt
- Brown de-icing salt impurities make it a weaker de-icer but do add some traction qualities
- White de-icing salt is a cleaner product than brown de-icing salt leaving no brown residue
- White de-icing salt is aesthetically more pleasing so more appropriate for public areas
- White de-icing salt has a higher concentration of salt than brown salt
- White de-icing salt is sourced from renewable sources