Pressure washer for driveway crack weed removal?

[Maddog]

If you already own one of those portable propane torches; you know, the kind you use to sweat pipe joints, etc. with, then go out and run the torch over the weeds. You won't be doing any visible damage to them, they will just move around like there is a light wind moving them. About a week later, they will be wilted and dead. I would go for the pressure washer at that point.

[OWC Jamie]

Most crack fillers are going to want the crack opened up. No sense killing the weeds before pulling them out.

Pressure washer to flush it all out, or screwdriver to open up crack and pull them out by hand, and/or with air pressure.

If you have decent pressure city water, that might be enough.
Depending on the size of the cracks and the reason for their existance, you may be better off with a pliable temperature flexible rubber/vinyl crack filler, rather than concrete patch on concrete.

If there is any asphalt, don't use solvents. Even a flame can ruin the asphalt, if you get it too hot.

On my concrete sidewalk, I've just used hose water pressure and pulled the big weeds by hand.

[Jp!]

It is my understanding that roundup becomes inert upon soil contact.