There is a large concrete spillway that was recently completed in northern Arizona, along Hwy 89. It’s designed to carry large amounts of water and it’s no small project. Though it started out grey, it’s not your typical grey concrete finish. They treated the concrete with something that caused it to start rusting, leaving it with an organic rustic appearance. It looks as if every inch of the concrete is rusting. I would like to duplicate this process. Does anyone know how to encourage this rust finish?
The Spillway is in Hell’s canyon near Drake Az. If you look on google earth, it shows up as the newly finished grey, but if you look at the attached pic or link, it shows how it is now rusting.
Thanks for your help.