When I built my track 3 years ago in a few spots around the track I built up the area leading up to the track edge with play sand just to do something different. I didn't do the whole track cause I didn't know how it would hold up and I didn't want sand all over the track. I then sprayed it with the Elmer's glue mixture to seal it. I never gave it a second thought until I redid a section of track and pulled everything up. I literally had to use a scraper and hammer to get this concrete like mixture up. Who would have thought. Nothing ever broke off and got onto the track.
Don't be afraid to use your imagination and try something new. When the new section of track is down and running I've got about 10 lbs. of railroad ballast from my train days I'm gonna use.
Dave