If you have polyurethane on your stone pavers, you will have to do a bit of work to do to remove it. If the polyurethane is still wet, you can wash it off the stone pavers with warm water with a bit of soap in it. Dried polyurethane can be more difficult to remove. You can scrub it of using a metal bristled brush or sand it with course sandpaper disc on an electric sander. Be sure to wear protective eye covers when doing this in case a chip of the paver breaks loose.