It’s downcycling into pavers and roofing tiles, which is pretty much the most you can hope for with soft plastics with today’s technology.
The resulting products cannot be used for anything else after they wear out.
To say nothing of leaching chemical runoff, questionable longevity of the bricks/tiles, shedding microplastics, inconsistent mechanical properties limiting use as construction materials, etc.
This process of shredding plastics, melting, adding sand, and shoveling into molds, has been known for a long time, and there are numerous videos showing entrepreneurs in 3rd world countries using it.