The technique for using grout for HO yard cinder ballast was described in these forums about a year ago. I copied the text for my own reference files (see below) but didn't keep the post or author information. There was a photo showing the results and it was impressive.
Jim
For yard ballast - I use 2 colors. Both were bought at Home Depot. The brand is PolyBlend Sanded Grout. #156 Fawn and #09 Natural Gray. They come in 7 lbs. bags and cost $7 and change. I use the Fawn as a basic dirt ground cover. The Natural Gray seems to be a good color and texture for gravel. They can also be mixed together.
I place the grout where I want it, then spray it with wet water only, no glue. After this has dried the grout will stay in place, up to a point. Remember it is cement. Any lumps and bumps can be smoothed out with the tip of your finger or a piece of fine sand paper . When things look ok., I spray some more wet water, then apply the dilute glue.
If at this point if I see something that's not quite right, I leave it until the glue has dried then fix it.
The other option is to make the fix while the glue is still wet. The risk here is disturbing other areas making more work.
It bears repeating that you should try these techniques with scrap materials first before using them on the real thing. Every time I have ignored this advice whether model building or making home repairs, I have regretted it.
Grout will get very hard and crack with the least bit of movement. It will probably also act like a drumhead and amplify the sound of trains on the track.
I tried it for the end of a siding in a scrap yard. I didn't like the result very much.
Unlike ballast, which is fairly loose and has room for glue to get between the pieces, grout is very fine and water doesn't penetrate well. So, the instructions say to mix it thoroughly. Then, you need to apply it as a paste. If you try to do that over track, it will end up on top of the ties, but it won't brush off like dry ballast.
It takes an iron man to play with a toy iron horse.
Ahoy,
Has anyone tried using colored grout for ballast? I work in n gauge and it seems to be close to model railroad ballast and all you need to do is spread it, and then spray water on it.