Why do highway workers spread calcium on the roads?
The highway workers are spreading calcium chloride, not calcium.
It absorbs huge amounts of water vapour from the atmosphere.
Highways Departments use these hygroscopic properties to keep a liquid layer on the surface of dirt roads.
This keeps the finer dust particles on the road.
If the dust particles are allowed to blow away, the larger particles begin to shift around, and the road breaks down.
Although calcium chloride can be applied in granular form, it is more frequently applied as an aqueous solution.