Horticultural vinegar? Or, rake it all out, lay out weed block, rake it all back in. won't keep out new seeds though.

Sounds really cool though.

~dianne

Echo - if I was a smart-alack I'd say invite me over to plant tomatoes in your driveway - that way we'd guarantee nothing will grow there - I can't get them to grow anywhere.

If you are really against RoundUp a mixture of vinegar and salt will kill the weeds. Just be careful, if it leaches into your yard it will kill everything there also. I tried it once and then went back to RoundUp.

http://www.garden-counselor-lawn-care.com/vinegar-weed-killer.html

After you get all the weeds out there is a sand with an additive they use with the pavers that dries hard like concrete. You might spread that over the shells and water it in. You'd have to ask around at the box stores about it's name.