cement sand and water ratio

Sand? - how do they stick to the wall?

:-p

I think you mean paving slabs / flags? If you do mean paving, then it's not too important how strong or weak the mix is, only that the surface that you are putting the mix on is sound and well compacted. If there is sand underneath them now and they have settled, your best idea (once you've taken them all up of course!) would be to sprinkle a few spadefulls of cement over an area of about 3 sq metres and rake it into the sand, (this will set into a firm base after a few days) and then lay your 'blobs' of mix on this base and lay the paving as normal, you can tramp down the dry sand/cement bed first to make it flatter for working on, or if you are good at laying paving, don't use blobs but just lay them on the unfirmed bed, but be warned - you won't get them down any further than 5mm, with blobs (fairly dry) you have an inch to play with. The mix that you make for the blobs can be as weak as 10 to 1 or as strong as 1 to 1 but it makes no difference whatsoever, it's not actually doing anything apart from acting as a spacer, unless you intend driving over them and then it's a totally different kettle of fishes.