Multi surface tracks are good - it adds to the off road experience
it works well for 8th scale as they do at Herts with no real increase in tyre wear.
If you can have a multi surface track with out a noticeable increase in tyre wear you will be on to a winner!
mind you, it doesnt need to be concrete/stone - you could experiment with kiddies outdoor 'soft play' flooring and/or interlocking garage/workshop floor tiles and/or a painted concrete for a change in surface.