Where Drive meets lawn

Not sure if this is "Building" or "Gardening" Forum...

I have a tarmac drive that meets the lawn. The lawn keeps encroaching (sp) over the drive as there is no edging/kerbstone. I have inserted a concrete edging kerb after excavating and haunched it with concrete. My question is, as this is done after the drive is tarmac'd, is there a way to stop weeds forming between the concrete edging kerb and the tarmac? It's like I need to seal between the tarmac drive and the kerbstone.

Any thoughts?

Thanks

you will find it difficult to get a successful seal.

seeds will fall into the smallest of cracks and germinate. it will seem like the grand canyon meets garden of Eden to wind blown seeds and stuff.

you could try pointing with black dyed mortar but this could be messy against the edging kerb.

Thanks Noseall,
I think I could do with a DIY "hot tar kit" if such a thing exists. Apply this to the edge after masking off the kerb?

If the gap is very tight you could use black mastic. It may discolour at a different rate to the tarmac though.