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In the UK, unlike some countries further north in the hemisphere, we don’t experience ice, snow, and extreme winter weather every year. However, the possibility of snow and ice means that, as a country, we must be fully prepared by the time winter rolls around.
This preparation is crucial for public safety and the smooth operation of transportation networks. Ensuring communities have access to road salt and grit is essential for protecting roads from damaging ice and snow, which can put pedestrians and vehicle users at significant risk.
This article explores the role of road salt and grit in road safety, delving into how it works by lowering the freezing point of water and analysing its effectiveness in preventing ice formation on road surfaces.
How Does Salt Melt Ice?
Before diving into how road salt works, let’s take a closer look at the science behind salt and how it melts ice. The freezing point of water is 0 degrees Celsius, at which point it will turn into ice.At 0 degrees Celsius, an icy surface will generally have a thin layer of water on top of the ice, where the ice and water molecules are interacting. Some of the water molecules melt the ice, and some of the ice molecules freeze the water.
Temperature changes affect whether this stable balance of melting and freezing is interrupted. When temperatures drop below 0 degrees Celsius, more water will turn into ice, but if temperatures rise, more ice will melt, turning into water.
However, when salt is added to the water, the freezing point becomes lower; this is a process called freezing point depression, which prevents water from freezing unless the temperature drops below minus 18 degrees Celsius.
So, how exactly does salt lower the freezing point? Well, salt disrupts the water molecules’ ability to lock into a rigid structure. As salt is soluble in water, when it dissolves, it breaks down into individual ions. These ions interfere with water molecules, making it more difficult for the water to form solid ice crystals.
The percentage of salt in a water solution dictates the temperature at which the water will freeze. A solution with 10 percent salt will freeze at minus 6 degrees Celsius, while a 20 percent salt solution will freeze at minus 16 degrees Celsius.
How Does Road Salt Work?
Now that we understand how salt interacts with water to decrease its freezing point, how can we harness the freezing point depression process to treat icy roads with road salt? As mentioned, salt relies on a layer of water to dissolve into the water and separate the ions to lower its freezing point. When roads aren’t entirely frozen, the salt can act instantly to begin lowering the freezing point of the water and melting the ice.
However, if road salt is applied to an already completely frozen road, there is no water layer for the salt to dissolve in, reducing its effectiveness in melting the ice. Let’s take a look at the two different road-treating strategies that can be followed to ensure salt is effective at melting ice.
Treat and Wait
When salt is spread on frozen roads using specialised machinery, it relies on the sun to melt the top layer of ice or the friction of car tyres driving over the ice to begin the melting process by turning the ice into slush. Once the ice has turned into slush, the salt can mix with the molecules, preventing the ice from refreezing.
Pretreating with Rock Salt
When snow is forecasted, many trucks begin pretreating the roads by laying road salt before the extreme weather arrives. Pretreating with solid salt relies on the warmer road surface to begin the melting process so that it can properly mix with the salt. This is also why pre-treatment of bridges, which are typically colder than other roads, is often ineffective and why the public is warned of this by “bridge freezes before road” signs.
Pretreating With A Brine Solution
Since salt requires water for freezing point depression to work, a brine solution (a mixture of salt and water) can be used to pretreat the roads. This solution with dissolved salt will prevent ice from forming and will reduce the quantity of solid salt required to de-ice the roads later on.
What is the Difference Between Regular Salt and Road Salt?
Road salt is similar to the table salt we use to season our food, as both are sodium chloride (NaCl). However, road salt is rock salt in its natural form. While table salt undergoes an extensive purification process to make it safe for consumption, road salt has more impurities. This is why it is often a brownish-grey colour rather than the bright white salt we consume.
There are also various salt mixtures that can be used in the same way. These include potassium chloride (KCl), magnesium chloride (MgCl), and calcium chloride (CaCl2). On icy roads, sodium chloride is the most common salt used to treat ice and snow due to its cost-effectiveness.
However, calcium chloride is actually more effective than sodium chloride in freezing point depression. While sodium chloride splits into just two ions, calcium chloride splits into three ions (one calcium ion and two chloride ions). More ions mean more interference with the water molecules, making it even harder for ice to form.
Alternatives to Road Salt
Sharp sand is a primary aggregate that offers a practical alternative to road salt in icy winter conditions. Unlike salt, which actively melts ice by lowering the freezing point of water, sharp sand functions by improving traction. By laying sharp sand over icy surfaces, roads gain a gritty texture that reduces the risk of vehicles sliding, helping drivers maintain better control and navigate safely on slippery surfaces.
Additionally, sharp sand helps to prevent further ice formation. When spread across roads and pavements, the movement of the sand grains makes it difficult for water molecules to stick together and form ice.
The key advantage of using sharp sand is that it’s less harmful to the environment than traditional road salt. Salt runoff from roads can infiltrate soil and waterways, harming plants and aquatic ecosystems. Sharp sand, however, has a neutral environmental impact since it does not dissolve into the ecosystem. In addition, it doesn’t corrode vehicles, metal infrastructure, or concrete the way salt can, making it safer for use in urban settings, residential zones, and environmentally protected areas.
Although reapplication is often necessary after heavy snowfall, sharp sand remains a cost-effective solution for communities looking to reduce the environmental impact associated with road salt use. While sharp sand does not actively melt ice, it effectively creates traction on icy surfaces, reducing the risk of slipping and sliding. By preventing ice buildup, it complements road salt, enhancing winter road safety and providing a safer, more environmentally friendly alternative that can be applied alongside traditional de-icing methods.
How Aggregate Suppliers Like Mark Luck Can Help with Winter Road Safety
Aggregate suppliers like us at Mark Luck Ltd play a crucial role in supporting winter road safety by providing essential materials like road salt and sharp sand. With a well-established fleet, including articulated lorries, we provide reliable road haulage services to deliver these vital products where they’re needed most.
From sharp sand, a primary aggregate that creates traction on icy roads, to road salt, which effectively melts ice and prevents it from refreezing, we have the materials to keep roads safe in winter. Our experienced logistics team ensures that these materials are available promptly across the region, even during peak winter conditions. Our reliable road haulage services allow for the efficient distribution of bulk road salt and sharp sand, supporting communities, construction sites, and private clients.
By delivering quality aggregates and road gritting supplies, we’re proud to help keep roads accessible, making winter travel safer and more manageable across the UK. To learn more about our road haulage services or inquire about our aggregates and road salt, get in touch with our friendly team today!
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