Homegrown hardscape: our very own urbanite
In the true spirit of One Blockedness, I’m thinking that the major renovation project I’m watching unfold can be the basis for recycled hardscape project in the test garden.
We are redoing the path that runs along our entire grounds. It’s cracked and uneven, making it semi-unsafe for anyone with mobility challenges.
Demolished concrete, called urbanite, is often repurposed into the retaining walls for raised beds. Our path is made from painted asphalt. I imagine it’ll hold more heat than concrete. Too much heat? Guess we’ll find out next year!
So, do you have a pile of asphalt in the corner of the Sunset garden waiting for a wall to be built, or did you send it off to the crusher to be recycled into something else?
Asphalt is basically gravel with tar and diesel. Sure the fumes are bad while in process but the tar and diesel formed in the asphalt doesn’t disappear. Plant can reuptake any nutrients in soil. It is a little more emerging science. Granted I think the asphalt would need to be extremely heated to release the oil/diesel it was made with, and even then the plant reuptake may be minimal but kind of suprised someone from CDC had such a brush off response.
Still feels not quite right. The study did mention skin cancers developing on animals that had come into contact with asphalt. You would probably be in contact with the wall while planting and caring for the garden. I would also wonder if chemicals leaching out of the asphalt might stunt the growth of some plants. If this really worked, why don’t we see lots of asphalt retaining walls???
I would also wonder if the blocks of asphalt might deform on a very hot day as they will not have a uniform support system (like a road bed) if they are stacked.
You both raise an excellent question — one I had myself. I wasn’t finding anything super concrete (no pun intended) online, so I asked Jim McCausland — one of our experts:
“The National Institute for Occupational Safety and Health says that the threat from asphalt is in the fumes, and you don’t get those by eating something grown near asphalt.
Plant roots generally absorb what they need, and there’s no nutrient or heavy metal that I can think of in asphalt that plants would want. Further, I can’t think of any toxic chemical in asphalt that plant roots would take up and concentrate in leaves or fruit—and that’s what would have to happen for an asphalt border around a raised bed to hurt you.”
Here is the link he provided:
http://www.cdc.gov/niosh/docs/2001-110/
What do you guys think? Convinced or still feels not quite right? I’m interested in knowing your thoughts!
That’s what I was thinking. Concrete is one thing, but asphalt seems like a pretty toxic product to have your plants in.
I would be more worried about the asphalt being an oil byproduct which is mixed with aggregate. Will bits break off into your vegetable beds? Do you want to eat food grown next to this stuff?