Road salt

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An Econ-brand salt spreader spreading salt on a road during the 2010 UK winter. Econ Salt Spreader.jpg
An Econ-brand salt spreader spreading salt on a road during the 2010 UK winter.

Road salt (also known as de-icing salt or snow salt) is a salt used mainly as an anti-slip agent in winter road conditions, but also to prevent dust and snow build-up on roads. [1] Various kinds of salts are used as road salt, but calcium chloride and sodium chloride (rock salt) are among the most common. [2] [3] The more expensive magnesium chloride is generally considered safer, but is not as widely used because of its cost and effect on structural integrity. [4] [5] When used in its solid form, road salt is often pre-wet to accelerate the ice-melting process. [6]

Contents

Spreading

Road salt and brine are generally spread using a winter service vehicle called a salt spreader. Salt spreaders are typically added to trucks, loaders, or in the case of brine, tankers. The salt is stored in the large hopper on the rear of the vehicle, with a wire mesh over the top to prevent foreign objects from entering the spreading mechanism and hence becoming jammed. The salt is generally spread across the roadway by an impeller, attached by a hydraulic drive system to a small onboard engine. However, until the 1970s, it was often spread manually either by workers shoveling salt from the back of the truck or by smaller wheelbarrow-like contraptions, [7] the latter still being used today for personal use. [8] Some older spreading mechanisms still require it to be manually loaded into the impeller from the hopper.

Mechanics

Salt for use of melting ice and snow works through a phenomenon called freezing-point depression, the lowering of a substances freezing point after the addition of solutes. When road salt is added to roads, aside from providing better friction for vehicles on the road, it also dissolves in the water of the ice, resulting in a lower freezing point. As long as the temperature is above this freezing point, this in turn results in the ice melting. [9] [10] Because of this, ordinary rock salt is only effective down to a range of −6 to −10 °C (21 to 14 °F). At colder temperatures, it can have the opposite effect. Road salt is sometimes used even in colder conditions, if milder weather is expected. In very cold and dry weather, the road surface becomes rough and the need for de-icing is reduced. However, during extreme cold and rain, the roads can become extremely difficult to pass and, in some cases, roads may need to be closed to traffic. [11]

Types of salt

Storage tank for road salt in Puente de los Hocinos, Spain. Road salt storage - N211- Teruel, Spain.jpg
Storage tank for road salt in Puente de los Hocinos, Spain.

Sodium chloride

Sodium chloride is by far the most common kind of road salt. This is mainly due to its widespread use and low cost, and thanks to its large industrial infrastructure, [12] it is used in many industrial and consumer applications. [13] While it is common and inexpensive, its effective temperature range usually does not go lower than −6 to −10 °C (21 to 14 °F), and under these temperatures, it is often counter-productive. When used in large quantities, it can also disrupt local ecosystems by heightening the salinity of bodies of water and the soil. Further, rock salt's abrasive nature erodes concrete or asphalt if used heavily. [1] [14]

Calcium chloride

Calcium chloride is less common compared to sodium chloride. While it is slightly more expensive than its sodium-based counterpart, it can cover a far larger area and melts ice almost three times quicker. [15] It has recently started rising in popularity since it is not as environmentally damaging as sodium chloride, and also because of its heightened effectiveness at clearing ice. [16] [17]

Magnesium chloride

Magnesium chloride is more expensive by far than the road salts in common use today. It has a very low environmental impact, and is quite effective at clearing ice. However, it has been discovered that magnesium chloride causes far more damage to concrete surfaces compared to the other salts, and has therefore been largely stopped being used as a de-icer. [4] [5] It is still widespread as a dust clearer in warmer weather, and is highly effective at it. [18]

See also

Related Research Articles

<span class="mw-page-title-main">Salt (chemistry)</span> Chemical compound involving ionic bonding

In chemistry, a salt or ionic compound is a chemical compound consisting of an assembly of positively charged ions (cations) and negatively charged ions (anions), which results in a compound with no net electric charge. The constituent ions are held together by electrostatic forces termed ionic bonds.

The term chloride refers to a compound or molecule that contains either a chlorine anion, which is a negatively charged chlorine atom, or a non-charged chlorine atom covalently bonded to the rest of the molecule by a single bond. Many inorganic chlorides are salts. Many organic compounds are chlorides. The pronunciation of the word "chloride" is.

<span class="mw-page-title-main">Brine</span> Concentrated solution of salt in water

Brine is water with a high-concentration solution of salt. In diverse contexts, brine may refer to the salt solutions ranging from about 3.5% up to about 26%. Brine forms naturally due to evaporation of ground saline water but it is also generated in the mining of sodium chloride. Brine is used for food processing and cooking, for de-icing of roads and other structures, and in a number of technological processes. It is also a by-product of many industrial processes, such as desalination, so it requires wastewater treatment for proper disposal or further utilization.

<span class="mw-page-title-main">Sodium chloride</span> Chemical compound with formula NaCl

Sodium chloride, commonly known as edible salt, is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chlorine ions. It is transparent or translucent, brittle, hygroscopic, and occurs as the mineral halite. In its edible form, it is commonly used as a condiment and food preservative. Large quantities of sodium chloride are used in many industrial processes, and it is a major source of sodium and chlorine compounds used as feedstocks for further chemical syntheses. Another major application of sodium chloride is deicing of roadways in sub-freezing weather.

<span class="mw-page-title-main">Sodium carbonate</span> Chemical compound

Sodium carbonate is the inorganic compound with the formula Na2CO3 and its various hydrates. All forms are white, odourless, water-soluble salts that yield alkaline solutions in water. Historically, it was extracted from the ashes of plants grown in sodium-rich soils, and because the ashes of these sodium-rich plants were noticeably different from ashes of wood, sodium carbonate became known as "soda ash". It is produced in large quantities from sodium chloride and limestone by the Solvay process, as well as by carbonating sodium hydroxide which is made using the chloralkali process.

<span class="mw-page-title-main">Calcium chloride</span> Chemical compound

Calcium chloride is an inorganic compound, a salt with the chemical formula CaCl2. It is a white crystalline solid at room temperature, and it is highly soluble in water. It can be created by neutralising hydrochloric acid with calcium hydroxide.

<span class="mw-page-title-main">Black ice</span> Thin coating of glazed ice on a surface

Black ice, sometimes called clear ice, is a coating of glaze ice on a surface, for example on streets or on lakes. The ice itself is not black, but visually transparent, allowing the often black road below to be seen through it and light to be transmitted. The typically low levels of noticeable ice pellets, snow, or sleet surrounding black ice means that areas of the ice are often next to invisible to drivers or people walking on it. Thus, there is a risk of slippage and subsequent accident due to the unexpected loss of traction.

<span class="mw-page-title-main">Magnesium chloride</span> Inorganic salt: MgCl2 and its hydrates

Magnesium chloride is an inorganic compound with the formula MgCl2. It forms hydrates MgCl2·nH2O, where n can range from 1 to 12. These salts are colorless or white solids that are highly soluble in water. These compounds and their solutions, both of which occur in nature, have a variety of practical uses. Anhydrous magnesium chloride is the principal precursor to magnesium metal, which is produced on a large scale. Hydrated magnesium chloride is the form most readily available.

<span class="mw-page-title-main">Freezing-point depression</span> Drop in freezing temperature of a solvent due to the addition of solute

Freezing-point depression is a drop in the maximum temperature at which a substance freezes, caused when a smaller amount of another, non-volatile substance is added. Examples include adding salt into water, alcohol in water, ethylene or propylene glycol in water, adding copper to molten silver, or the mixing of two solids such as impurities into a finely powdered drug.

<span class="mw-page-title-main">Snow removal</span> Job of removing snow

Snow removal or snow clearing is the job of removing snow after a snowfall to make travel easier and safer. This is done both by individual households and by governments institutions, and commercial businesses.

<span class="mw-page-title-main">Deicing</span> Process of removing ice, snow, or frost from a surface

Deicing is the process of removing snow, ice or frost from a surface. Anti-icing is the application of chemicals that not only deice but also remain on a surface and continue to delay the reformation of ice for a certain period of time, or prevent adhesion of ice to make mechanical removal easier.

<span class="mw-page-title-main">Grit bin</span> Roadside container for a mixture of salt and grit

A grit bin, salt bin or sand bin is an item of street furniture, commonly found in countries where freezing temperatures and snowfall occur, which holds a mixture of salt and grit that is spread over roads if they have snow or ice on them. Spreading rock salt over roads and pathways is commonly done either by hand or with a winter service vehicle and helps improve road safety in frosty conditions. The salt helps reduce the freezing temperature of the ice, which can be effective in temperatures of up to -9°C (16°F). Roads that are not gritted during winter are much more dangerous for vehicles and foot traffic, so busy routes can be gritted several times per day under harsh snowy conditions.

<span class="mw-page-title-main">Compass Minerals</span> Mineral company

Compass Minerals International, Inc is an American public company that, through its subsidiaries, is a leading producer of minerals, including salt, magnesium chloride and sulfate of potash. Based in Overland Park, Kansas; the company provides bulk treated and untreated highway deicing salt to customers in North America and the United Kingdom and plant nutrition products to growers worldwide. Compass Minerals also produces consumer deicing and water conditioning products, consumer and commercial culinary salt, and other mineral-based products for consumer, agricultural and industrial applications. In addition, Compass Minerals provides records management services to businesses throughout the United Kingdom.

<span class="mw-page-title-main">Sodium formate</span> Chemical compound

Sodium formate, HCOONa, is the sodium salt of formic acid, HCOOH. It usually appears as a white deliquescent powder.

Calcium magnesium acetate (CMA) is a deicer and can be used as an alternative to road salt. It is approximately as corrosive as normal tap water, and in varying concentrations can be effective in stopping road ice from forming down to around −27.5 °C (−17.5 °F) (its eutectic temperature). CMA can also be used as an H2S capture agent.

<span class="mw-page-title-main">Winter service vehicle</span> Vehicle used to clear snow and ice

A winter service vehicle (WSV), or snow removal vehicle, is a vehicle specially designed or adapted to clear thoroughfares of ice and snow. Winter service vehicles are usually based on a dump truck chassis, with adaptations allowing them to carry specially designed snow removal equipment. Many authorities also use smaller vehicles on sidewalks, footpaths, and cycleways. Road maintenance agencies and contractors in temperate or polar areas often own several winter service vehicles, using them to keep the roads clear of snow and ice and safe for driving during winter. Airports use winter service vehicles to keep both aircraft surfaces, and runways and taxiways free of snow and ice, which, besides endangering aircraft takeoff and landing, can interfere with the aerodynamics of the craft.

<span class="mw-page-title-main">Molten salt</span> Salt that has melted, often by heating to high temperatures

Molten salt is salt which is solid at standard temperature and pressure but liquified due to elevated temperature. A salt that is liquid even at standard temperature and pressure is usually called a room-temperature ionic liquid, and molten salts are technically a class of ionic liquids.

<span class="mw-page-title-main">Cooling bath</span> Liquid mixture used to maintain low temperatures

A cooling bath or ice bath, in laboratory chemistry practice, is a liquid mixture which is used to maintain low temperatures, typically between 13 °C and −196 °C. These low temperatures are used to collect liquids after distillation, to remove solvents using a rotary evaporator, or to perform a chemical reaction below room temperature.

<span class="mw-page-title-main">Frost flower (sea ice)</span> Ice crystal found growing on young sea ice

Frost flowers are ice crystals commonly found growing on young sea ice and thin lake ice in cold, calm conditions. The ice crystals are similar to hoar frost, and are commonly seen to grow in patches around 3–4 cm in diameter. Frost flowers growing on sea ice have extremely high salinities and concentrations of other sea water chemicals and, because of their high surface area, are efficient releasers of these chemicals into the atmosphere.

Soil stabilization is a general term for any physical, chemical, mechanical, biological, or combined method of changing a natural soil to meet an engineering purpose. Improvements include increasing the weight-bearing capabilities, tensile strength, and overall performance of unstable subsoils, sands, and waste materials in order to strengthen road pavements.

References

  1. 1 2 "Winter is Coming! And with it, tons of salt on our roads". www.epa.gov. 2021-03-08. Retrieved 2024-10-04.
  2. ↑ Rasevic, Paul (2018-10-12). "Comparing Calcium Chloride vs Sodium Chloride for Melting Ice and Snow". Snow & Ice Salt & Chemicals Unlimited. Retrieved 2024-10-04.
  3. ↑ "Calcium Chloride vs. Rock Salt. Which do you use?". Peters Chemical Company. Retrieved 2024-10-04.
  4. 1 2 "Magnesium Chloride As A Road Deicer: A Critical Review". Peters Chemical Company. Retrieved 2024-10-04.
  5. 1 2 "Magnesium Chloride - A worse road salt than Calcium Chloride". www.salt.no. Retrieved 2024-10-04.
  6. ↑ "The Trend of Pre-Wetting". SnowEx. Retrieved 2024-10-04.
  7. ↑ Hodgkinson, David (June 2000). "Editorial". Proceedings of the Institution of Civil Engineers - Municipal Engineer. 139 (2): 53–54. doi:10.1680/muen.2000.139.2.53. ISSN   0965-0903.
  8. ↑ "WB Walk Behind Spreaders". Snow Trading. Retrieved 2024-10-04.
  9. ↑ "Why Does Salt Melt Ice on the Roads in Winter?". HowStuffWorks. 1970-01-01. Retrieved 2024-10-04.
  10. ↑ Pollock, Julie. "Salt Doesn't Melt Ice--Here's How It Makes Winter Streets Safer". Scientific American. Retrieved 2024-10-04.
  11. ↑ "Vägsalt - bara där det behövs". Trafikverket (in Swedish). 2024-09-23. Retrieved 2024-10-04.
  12. ↑ "Salt Production and Processing". Morton Salt. Retrieved 2024-10-04.
  13. ↑ Schwartzberg, Ezra (2016-09-27). "The Hidden Costs of Road Salt". Adirondack Research. Retrieved 2024-10-04.
  14. ↑ "Common Types of Road Salt Explained". Ninja De-Icer. 2024-04-08. Retrieved 2024-10-04.
  15. ↑ "Should you use calcium chloride on roads?". Eco Garden Solutions. 2020-09-27. Retrieved 2024-10-04.
  16. ↑ "Road Treatment – Information about Calcium Chloride". Peters Chemical Company. Retrieved 2024-10-04.
  17. ↑ "Calcium Chloride versus Rock Salt". Snow & Ice Salt & Chemicals Unlimited. 2022-06-27. Retrieved 2024-10-04.
  18. ↑ "Magnesium chloride – Salinity" . Retrieved 2024-10-04.
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