A compressible joint filler should be placed between a concrete slab edge and any vertical surface to avoid bonding and to allow for expansion. If the concrete is to exposed to the weather it should be "air-entrained" for greater durability. A sheet of 6x6 - 10/10 (6" square openings, 10 gague wire) welded wire mesh will help prevent cracking if it is placed at the mid point of the slab depth. Hold it up with concrete supports made for that purpose, don't lift it after the pour. Don't add water to the initial mix. The biggest mistake made by DIY'ers is to trowel the bleed water back into the slab which causes a weak surface which will usually result in a condition called scaling. After the initial sceeding either remove the bleed water or let it evaporate before finishing the concrete. It should be covered and/or kept wet while curing.
Last edited by mighty anvil; 10-06-2005 at 04:19 PM.