Home Depot sells this stuff that looks like MASONITE. It is Tan and smooth and is aobut 1/4 inch thick by 2 ,5 inces wide. It is not that expantion joint stuff. This is more dense. It is great for makeing forms especially curves as it bends easily. Plus it can be re used.
I will stop by home depot today and see if I can get a skeu number.\
Here is how I anchor my track
The wire is the stuff they use to tie rebar together. You can get it at Home Depot in a spool
It is cheap.
I drill a 1/4 in hole in the concrete road bed and insert the plastic anchor.
I bend a loop in a short piced of wire to fit around the screw.
Put the screw in the anchor and tighten.
I then bend the wire over the tie.
It holds pretty tight
Some times I take a longer piece of wire and make the loop in the middle for the screw
Then I bed it over to ties one on each side of the anchor.