Avoid getting Gravel-Lok® on adjacent surfaces because it is nearly impossible to remove it and will leave an unsightly stain. If Gravel-Lok® is still wet (not yet cured) then acetone could be used to remove it.
If Gravel-Lok® has already cured, a paint / stain varnish remover can work in some instances on smooth flagstones, concrete, or brick. Apply the stain / varnish remover to the area, let it rest for 5 minutes, then use a wire brush to remove the stain. It may be necessary to repeat this process.