By Kidsgran
Mid Glamorgan,
Wales 
I sprayed my drive which is laid with blocks with weed killer as it was covered with what looked like self seeded grass it killed off the weeds but they are to difficult to remove even with a power washer they are tough to pull out and to many to pull out by hand the drive is 80 ft long any suggestions welcome thank you .
12 Aug, 2018
Answers
If you just wanted to kill your mosses and lichens you need a specialised killer. It is only then that your pressure washer will remove them. A higher pressure washer would do the trick though or you could take everything out with a raking tool or wire brush on a shaft. If it's only the treated grass that you are worried about, it will disappear on its own given time.
12 Aug, 2018
Thank you both can't see myself in charge of a flame gun 🤔 and yes it is only the treated grass that is making the drive look a little unkept so will hope it will disappear I time .
12 Aug, 2018
A good, stiff broom.
12 Aug, 2018
You might need to re-sand the joints if pressure washing washes some out. Sending sympathy as I have the same problem with moss (worse than yours if that's any comfort...) and I was thinking of using hyperchlorite and chancing a stiff brush afterwards.
12 Aug, 2018
Get a gas powered flame gun from somewhere like B&Q and burn the tops down.
12 Aug, 2018