Polyethylene is a wonderful material for subtractive manufacturing, especially parts that you might otherwise 3D-print or make out of wood.
It's easy to make "bricks" by melting and pressing chips and shredded material in a mold, and those bricks make excellent machine stock.
You can't use it as a building material, but I like the idea of mixing in sand and using them as paving stones. After all, we frequently pave playgrounds with flammable material made out of shredded tires.
I do wonder about microplastics flaking off of them, though. PE is pretty remeltable, but like most plastics it gets a bit more brittle with every cycle. Most recycling outfits mix some virgin plastics in with the recycled stuff for that reason.