Creating a concrete floor and pad for my HO scale car shop

One of the new parts of the upgraded yard will be the slightly relocated car shop that is now also serving as the caboose servicing area. I wanted a large concrete area between tracks where you could have lots of little detail bits and repair work going on. When choosing a material, I've been using a lot of insulation foam as of late, and I found it worked well. This particular piece was a thin section of one of the "fan fold" types that I often use for walls and detail bits.

Here's the test fitting of the foam piece. The caboose track is the angled track closest and the car repair (RIP) track is along the back wall. 

Another angle.

Here you can see the little triangular piece I cut so the pad would stretch to the end of the caboose track.

So here's the starting point, a plain piece of foam.

I painted it a concrete color and added lines using a fine point art marker. Note that there is a bit of an optical illusion going on here -- the lines are straight, not converging. Cover the non-foam part of the photo with your hand if you don't believe me.

Added in some cracks.

Went over everything with primarily some white chalk with some browns and black here and there to tone all the lines down.

The foam glued in place.

And with the building back on and a few cars.

Another angle. There are more detail bits now, but these photos are from almost a month ago at this point.