Filling gaps between concrete slabs - HELP!

Sand & cement is the usual thing. The best is epoxy mortar but far to expen sive for 1" gaps.

The usual method is mix it dry with dried sand, brush into the gaps & leave to get damp & set. You might want to follow with a little tool pressing it down flat for better strength.

NT

Sand and cement mortar - with added colouring if required. Mix it with very little water so that it can't stain the slabs - you can add some plasticiser like feb mix to make it more workable. It want to be just wet enough to stick together if you squeeze it into a ball.

Work it will into the gaps and trowel it in with a narrow pointing tool or trowel. If any gets on the slabs, leave it to dry - on a hot day it will dry out before it gets a chance to hydrate properly, and hence will not cure properly - it will be crumbly and easy to brush off the surface later.

It will be more expensive than mortar, but Easyjoint is pretty simple to use:

I used Wickes self-setting patio grout. You just brush it into the gaps. One year later, it seems to have worked OK, but I wish I'd been a bit more assiduous in working it in, since a few gaps have appeared. But I didn't want to have to do it on my hands and knees.

Bit worried about why there are such big gaps, one might expect such things in crazy paving but not slabs. Is it moving due to having no edging fixed in place? If so I suspect any filling of the gaps will be at best temporary for this year. Brian

Scrapped out gaps that only have mud in the bottom suggest that maybe the slaps may have just been laid straight on to bare ground.

replying to Brian Gaff, KellyAS wrote: They are huge square concrete slabs that must have been here for decades. They?re not moving anywhere. Heavy as hell and no idea how deep they go

From the sound of it they may have been poured onto bare ground, and the gaps are where the shuttering was.