My father actually ran a plastic waste recycling business similar to this about 20 years ago. He didn’t add any filler to the plastic so it was just ground up a

My father actually ran a plastic waste recycling business similar to this about 20 years ago. He didn’t add any filler to the plastic so it was just ground up and run through an extruded and then injected into moulds. He mostly made beams and boards. The business didn’t survive but we still have a number of the plastic boards and beams. They’ve been in continuous use on his property for the past two decades in various incarnations as fencing, shed walls, sleepers used for keeping material off the ground, etc. They haven’t degraded as far as I can tell although they might be slightly lighter in colour. Only some of the 2x6 boards deformed and broke when they were used as a fence but I think that has more to due with livestock pushing up against them. These bricks will probably work fine as foot paths, the sand and dye in them will slow UV degradation and foot traffic is unlikely to wear them much. I wouldn’t build a house out of them, offgassing would be a bigger concern for me than sagging, at least on a 1 story structure. A brick is a widely useful thing so I hope her business does well. She’s essentially just making plastic composite which is something you’re seeing in North America now used for decking.