Cement can be messy to work with, especially if you're a new do-it-yourselfer. When you realise you've got some cement splatter on your newly laid paving stones, don't think you have to live with it. Clean up the cement while it's still wet or, if it's mostly set, wait until it's dried to clear up the mess. You should be able to get your paving stones back in good shape.
Scrape up any concrete mortar that is still wet, using a plastic scraper. Dispose of the waste in a rubbish bin.
Moisten a cotton rag, then run the rag over the cement splatter. If you've scooped up most of the cement and the cement is still wet, you may be able to finish the job by wiping the remainder up before it dries.
Clean again when the cement dries. If you clean and rinse the paving stones before then, you can damage the strength of the finished concrete. Some cement dries in two hours, while others take several more hours.
Wet the affected areas with water from a hose or spray bottle.
Add water to washing powder until it forms a paste. Using a scrubbing brush, spread this paste over the cement dribbles on your paving stones. Don't use a wire brush, because the bristles may scratch your paving stones. Wait several minutes.
Scrub the paste into the stained areas, then rinse away with fresh water. If your paving stones still display traces of dried cement, repeat this scrubbing technique one more time to remove any last bits.
If your paving stones are still not clean, pressure-wash them to remove any remaining traces of cement.