Bricks, Masonry, Asphalt and Concrete - Gap between cement (slab) floor and kitchen wall...

In my kitchen along the base of the outside wall (below the plaster between cinder block and cement slab) is a gap that ranges from 1/4 to almost an inch wide. I was about to fill it with a pliable concrete filler when I noticed that there seemed to be old pieces of fiber board (or something) down in there. Whatever it was rotted away some time ago. I don't know if it was a moisture block or what but the filler I bought couldn't possibly fill a crevace that deep.

Would it be ok to use an expanding foam? Would a bag of sacrete end up pushing the cinder blocks out? Should I just seal it at floor level and try to go to sleep pretending that everything's ok? *lol* All I really wanted to do was replace the baseboard and it seems to be turning into a project.

It's true that suitable flexible polyurethane foam fillers exist but they are not the same rigid insulation aerosol foam that you're referring to.

An easy fix is foam "backer rod" topped with a elastomeric sealant (polyurethane or silicone caulk or possibly Deck-O-Seal).

Foam backer rod is available in various diameters at masonry supplies and where fireplace products are sold. Select a size or sizes of rod that will span the gap with the slightest amount of compression. Do not jam pack the rod into the crack. Multiple stands of smaller rod may be used. Fill to about 5/8" below the surface.

Polyurethane and silicone caulks are available at any hardware store. Read the label to ensure the caulk is rated for use with concrete or masonry.

Deck-O-Seal is a brand name of a poured two component filler (aka: "pool poly") used mainly between swimming pool copings and the deck (swimming pool supply). One advantage, among others, is it spans gaps up to 2" easily. Apply masking or duct tape along the edges, mix, pour, remove tape.

If quizzed by a salesman tell them you're redoing a concrete expansion joint. If you want the real thing used in industry http://www.chemrex.com/sonneborn/product.asp From "Select Application" choose "Joints and Cracks" then click Go. Inexpensive? Not really.

Thank you. One more question though...Do i need to find a way to get the rest of the fiber board or what ever it is out of that gap?

Remove as much as possible. A old stout screwdriver work fairly well.