Photo 1 shows a great use for that otherwise useless 15mm wrench. It made a perfect screed to level the cement filler to about 3/8" depth.
Now I waited on the cement to dry thoroughly, about 3 days was enough. This is important since the rubber I used is a urethane product and urethanes will foam if exposed to free water. I used PL brand self leveling crack filler that comes in a light gray color. They also make a crack patching formula but it is a paste that must be troweled and won't self level. I simply squeezed it into the crack with my caulking gun and let it flow to level out in the crack. Photo 2 shows the result. I got about 7' from each caulking tube for my 1" x 3/8" slot. Once set up in about 3 days, it should be a permanent fix to those nasty cracks in my floor.
Oh, and I guess I need to show you details of my crack! Figure 3 is a sketch of three types of cracks you might encounter. the first is my super-expansion joint, the second is a typical small expansion joint (smaller but still needs to be filled. Be sure to caulk the bottom if there is a crack in the cement 'cause that crack will suck up all the expensive urethane.), and the third is a common big unplanned crack in the cement.
