While it is true that covering the curing concrete with plastic will keep it cleaner, there is a more essential purpose behind this practice: Remember, you mix water into concrete to activate the cement binding agent within. As the mix dries, it will harden. But the drying, or 'curing' should be gradual, otherwise cracking may occur. Frost heaves create hazardous and unsightly cracks in concrete slabs along a driveway, pathway or walkway. Left untreated, these cracks spread over the surface and make the slabs vulnerable to moisture damage. Concrete heaves when water underneath freezes, displacing the soil and damaging the slab.
My Driveway Is Cracking
Hairline cracks are common as a driveway ages and weather takes its toll. Cracks will continue spreading, widening, and deepening, which can lead to bigger problems down the road.
Dirt and water will work their way into the cracks. When the water freezes and expands, it causes the cracks to grow. Kent Hansen, director of engineering for the National Asphalt Pavement Association (NAPA) in Lanham, Md., says that simply putting an overlay atop the driveway won't solve the problem—the cracks will just come through it. Instead, the cracks need to be cleaned to remove any dirt and debris, and then, ideally, filled with a hot sealer, which is usually applied by a professional.
Jay Sutherland, owner of Expert Asphalt in Watertown, Minn., agrees, saying that a hot sealer is the only long-term solution, since the crack fillers sold at home centers are temporary fixes. 'To do it right, you have to heat the crack filler,' he says. 'It burns into the walls of the crack. When it cools, it expands and fills the crack. It's a permanent fix.'