Have tried using this product for ballasting N Gauge track - using fine-sieved san - and it holds together really well, even at that scale. There is a slight colourisation of the ballast when the product is dry, but it is very minimal and wouldn't be noticeable if you didn't see the ballast beforehand.
The solution applies to the ballast really easily using the very fine nozzle provided (which is easily rinsed clean between uses).
Recommended for ease of use and effectiveness at bonding fine ballast.