Sealing Concrete For Minnesota Winters One of the most important things you can do to protect your garage slab and driveway investment is to get a good cement sealer on it. According to Cemstone one of our suppliers, properly sealing all exterior flat work will help maintain the appearance and durability for many years. The sealer should be applied approximately 30 days after placement. Waiting 30 days insures the concrete has had adequate time to cure. It's very important to make sure your garage slab and driveway are sealed PRIOR to the first winter.