Tank you guys!
On that one in Decatur, AL, I can see the long siding with the string of covered hoppers on it, and there's a little building
part-way along that siding which must be where the unloader is. What is odd to me is that the actual
silo building (the one with the 3 tall tower silos, over where all the concrete trucks are),
is a long way away, all the way across the construction yard,
from the unloading area. So what do they do, truck it across the yard and then run it up conveyors into
the mix? That seems like a pain. Well, I'm taking some artistic license here, and trying to keep this thing small,
so there is a siding that runs right up next to the building with the silos. In my little world, they will park
a covered hopper of sand or cement there, and unload pneumatically right up into the silos, where it is stored.
Further down that same spur, they can park a regular hopper that will be unloaded from underneath by conveyor to dump the gravel into work piles in the yard.
A clamshell crane will pick up buckets of gravel and place them into a small hopper , that will feed the gravel out
onto a conveyor to carry the gravel up up into the silo building.
Now, how the amounts of cement, gravel, and sand are measured, well... I'll just pretend that magic happens inside the building
attached to the silos.
I'll take a few pics to post in here later that will make it clearer.