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The science of gritting | Sandwell Council

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The science of gritting

gritting crew small

  • Although we call it gritting, there is in fact little or no grit involved. What is actually spread on the roads is mined rock salt (sodium chloride).
  • The rock salt is spread on to the road in varying rates depending on how icy or snowy it is.
  • Rock salt needs vehicles to drive over it to work effectively. Vehicles grind the salt into smaller particles to spread it across the road - this means that grit is sometimes not effective when there isn't much traffic or when there is a lot of snow.
  • Water freezes at 0°C - the presence of the salt prevents water from freezing until -6°C to -8°C.
  • However, salt starts to become less effective at -5°C and almost ineffective at lower temperatures.
  • In extremely low temperatures, or heavy snowfall, a mix of salt and grit may be used to help vehicles get about.

Ploughing

  • Snow ploughs can be fitted to all of our gritting trucks.
  • Snow ploughing removes large accumulations of snow from the centre of roads.
  • However, ploughing has its limitations - it effectively skims the road surface leaving around 30-50mm of snow on the surface.
  • Ploughing can also result in large amounts of snow accumulating at the sides of roads and on footpaths.
  • Following prolonged periods of gritting, snow ploughing can reduce the overall effectiveness of de-icing operations by removing slush which has a high level of salt solution.