Thank you fit the reading material. Looks like is the way to go. I'm going to put off doing my roads until I can test this out.I use sanded grout with N scale ballast on spurs, sidings, ground-level track, terminal tracks, etc.
Sanded grout is powder-like stuff you can get at HomeDepot, Lowes, etc. It has a binder in it that keeps it in place instead of floating.
It comes in various colors, so you can mix to get one you like. I generally disregard the color, and tint with dry-earth colors.
If you Google "sanded grout for ballast" you'll get a lot of hits.
Here's a start:
(touch all the links in the first response).
Grout as ballast? (Grout for dirt roads & parking lots) | Model Railroad Hobbyist magazine
Any issues with cracking? As a former tile layer, I know thin grout can crack easily.
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