I also wanted to bring up Total Vegetation Management for anyone interested.
You know, killing all weeds and grasses on patios, gravel driveways, bike paths etc.... ON A LARGE SCALE.
How do you do this organically (safely) as opposed to (dangerous) RoundUP and without revisiting the job site every 2 weeks for the whole season.
I could go on about the major failures associated with steam, ammonium soaps of fatty acids, acetic acid, flames, goats.... (non systemic properties, regrowth, cost)
But there is probably a way to make a healthier gravel to resist weeds I bet.
Microbial activity of the rocks.