A long, long time ago I once made a cobblestone road using dried split peas for the stones. Gluing them to the wooden base with Elmer's glue. Labor intensive but cheap.
Then I painted it with enamels. No acrylics back then but they might of softened up the Elmer's.
Not much for dio materials back in the mid 70's.
Here's a thought.... I used drywall scraps for my buildings back then. I'd dampen one side until I could peel the paper off leaving the other side on to use as wall paper. Then I'd leave large areas plain to simulate a stucco finish but flake off some for damage and carve the bricks in. Sealing the surfaces with Elmer's so the paint wouldn't soak in. Wall thickness was totally out of scale but there really wasn't anything until Verlinden came along.
What I'm getting at is.... Take a piece of drywall and cut it to the area & shape that you need. Glue it to your base. Remove the paper and carve a way. Once again, cheap but labor intensive.
No seams to deal with like butting together a couple of MiniArt road sections. Although, I think that they do make a set with manhole covers and the such.
HTH !
Tom