Ralph and Chris, thanks for your informations.
Maybe that I have some difficulties with the translation of the proper expressions, but I think now can figure out what this plant does.
I suppose that this is a sort of a rotating oven in which the natural raw materials for cement (limestone and clay with aluminum oxide) are baked to 'clinker'. To get the cement powder we all know, this clinker is ground in huge ball mills.
Probably this aggregate plant does the baking of the clinker, which emerges as a dark grey mass from the kiln. (Looking at the dark heaps in your pics, Ralph, I thought the plant had something to do with coal industry!

)
As you said, the clinker has to be shipped to the cement plant where it is ground, mixed with some more chemicals and filled into bags...
The setting of your model now makes even more sense - it suggests that the limestone quarry is just around the bend from here. A great source for traffic on your layout!
Ron