Movatterモバイル変換


[0]ホーム

URL:


Jump to content
WikipediaThe Free Encyclopedia
Search

Road salt

From Wikipedia, the free encyclopedia
Salts used for de-icing road surfaces
An Econ-brand salt spreader spreading salt on a road during the 2010 UK winter.

Road salt (also known asde-icing salt,rock salt, orsnow salt) is asalt used mainly as an anti-slip agent inwinterroad conditions, but also to preventdust andsnow build-up onroads.[1] Various kinds of salts are used as road salt, butcalcium chloride andsodium chloride (rock salt) are among the most common.[2][3] The moreexpensivemagnesium 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 itssolid form, road salt is often pre-wet to accelerate the ice-melting process.[6]

Spreading

[edit]

Road salt andbrine are generally spread using awinter service vehicle called asalt spreader. Salt spreaders are typically added totrucks,loaders, or in the case of brine,tankers. The salt is stored in the large hopper on the rear of the vehicle, with awire 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 animpeller, attached by ahydraulic drive system to a small onboardengine. However, until the 1970s, it was often spread manually either by workersshoveling salt from trucks or by smallerwheelbarrow-like vehicles,[7] the latter still being used today for personal use.[8] Some older spreading mechanisms still require it to be manually loaded into theimpeller from the hopper.

Mechanics

[edit]

Salt for use of meltingice andsnow works through aphenomenon calledfreezing-point depression, the lowering of a substancesfreezing point after the addition ofsolutes. When road salt is added to roads, aside from providing betterfriction for vehicles on the road, it also dissolves in thewater of the ice, resulting in a lower freezing point. As long as thetemperature is above this freezing point, this in turn results in the icemelting.[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

[edit]
Storage tank for road salt in Puente de los Hocinos, Spain.

Sodium chloride

[edit]

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 largeindustrialinfrastructure,[12] it is used in many industrial andconsumer applications.[13] While it is common and inexpensive, its effective temperature range usually does not fall below −6 to −10 °C (21 to 14 °F), and under these temperatures, it is often counter-productive. When used in large quantities, it can alsodisrupt local ecosystems by heightening thesalinity ofbodies of water and thesoil. Further, rock salt's abrasive nature erodes concrete or asphalt if used heavily.[1][14]

Calcium chloride

[edit]

Calcium chloride is less common compared to sodium chloride. While it is slightly more expensive, 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

[edit]

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 moredamage to concrete surfaces compared to the other salts, and its use as a de-icing chemical has largely been discontinued.[4][5] It is still widespread as a highly effectivedust clearer in warmer weather.[18]

Enviromental impact

[edit]

The widespread use of road salt has significant environmental and infrastructural repercussions. While effective and relatively inexpensive, this practice incurs hidden costs because of its corrosive nature, leading to approximately $5 billion in annual repairs across the United States, according to the country'sEnvironmental Protection Agency.[19]

One of the primary environmental concerns is the contamination of water sources. Road salt can infiltratesurface andground water, elevating sodium and chloride levels in drinking water reservoirs and wells; one teaspoon of road salt can permanently pollute five gallons of water.[19] Elevated sodium levels pose health risks for individuals withhypertension, and high chloride concentrations are toxic toaquatic life.

The accumulation of salt in roadside soils adversely affects vegetation by increasing soil salinity, which can hinder plant growth and lead to the death of sensitive species. This degradation of plant life not only disrupts local ecosystems but also contributes to soil erosion. Additionally, wildlife attracted to the salt (such as deer and moose) can be endangered, as they may ingest harmful amounts or be drawn to roadways, increasing the likelihood of vehicle collisions. The term "Salt Belt" refers to regions with heavy road salt usage, predominantly in the northeastern United States. In these areas, the cumulative effects of salt application are more pronounced, leading to higher concentrations of salt in the environment and exacerbating the associated negative impacts.

Alternatives to traditional road salt are being explored to mitigate its environmental and infrastructural damage. While magnesium chloride and calcium chloride are considered less harmful to the environment, they are more expensive and may require higher application rates. Other strategies that help reduce salt usage and discharge into waterways include spraying road surfaces with brine in anticipation of snowfall, as well as mixing salt with other substances such as sand to improve traction, dyes to aid in identification of salted areas,[20] and biodegradables like beet juice, pickle juice, and molasses. Innovative solutions, such as porous pavements, have also been developed to reduce ice accumulation and minimize the need for de-icing agents.

See also

[edit]

References

[edit]
  1. ^ab"Winter is Coming! And with it, tons of salt on our roads".www.epa.gov. 2021-03-08. Retrieved2024-10-04.
  2. ^Rasevic, Paul (2018-10-12)."Comparing Calcium Chloride vs Sodium Chloride for Melting Ice and Snow".Snow & Ice Salt & Chemicals Unlimited. Retrieved2024-10-04.
  3. ^"Calcium Chloride vs. Rock Salt. Which do you use?".Peters Chemical Company. Retrieved2024-10-04.
  4. ^ab"Magnesium Chloride As A Road Deicer: A Critical Review".Peters Chemical Company. Retrieved2024-10-04.
  5. ^ab"Magnesium Chloride - A worse road salt than Calcium Chloride".www.salt.no. Retrieved2024-10-04.
  6. ^"The Trend of Pre-Wetting".SnowEx. Retrieved2024-10-04.
  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. Retrieved2024-10-04.
  9. ^"Why Does Salt Melt Ice on the Roads in Winter?".HowStuffWorks. 1970-01-01. Retrieved2024-10-04.
  10. ^Pollock, Julie."Salt Doesn't Melt Ice--Here's How It Makes Winter Streets Safer".Scientific American. Retrieved2024-10-04.
  11. ^"Vägsalt - bara där det behövs".Trafikverket (in Swedish). 2024-09-23. Retrieved2024-10-04.
  12. ^"Salt Production and Processing".Morton Salt. Retrieved2024-10-04.
  13. ^Schwartzberg, Ezra (2016-09-27)."The Hidden Costs of Road Salt".Adirondack Research. Retrieved2024-10-04.
  14. ^"Common Types of Road Salt Explained".Ninja De-Icer. 2024-04-08. Retrieved2024-10-04.
  15. ^"Should you use calcium chloride on roads?".Eco Garden Solutions. 2020-09-27. Retrieved2024-10-04.
  16. ^"Road Treatment – Information about Calcium Chloride".Peters Chemical Company. Retrieved2024-10-04.
  17. ^"Calcium Chloride versus Rock Salt".Snow & Ice Salt & Chemicals Unlimited. 2022-06-27. Retrieved2024-10-04.
  18. ^"Magnesium chloride – Salinity". Retrieved2024-10-04.
  19. ^abUS EPA, REG 01 (2021-03-08)."Winter is Coming! And with it, tons of salt on our roads".www.epa.gov. Retrieved2025-01-18.{{cite web}}: CS1 maint: numeric names: authors list (link)
  20. ^"Why Road Salt Is Blue? - Canada Salt Group Ltd".Canada Salt. 2020-10-30. Retrieved2025-01-18.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Road_salt&oldid=1276317947"
Categories:
Hidden categories:

[8]ページ先頭

©2009-2025 Movatter.jp