Frost heaving, common in cold climates, forces concrete slabs out of the ground. Sunken concrete is usually caused by erosion of the subbase. General surface deterioration results from "overfloating", which draws too much water to the surface and causes the concrete to weaken and peel. Overfloating is also a common cause of hairline cracks or "crazing." Cleaning and sealing the surface will help prevent further crazing, but the long-term solution is to resurface.

Whatever the cause, it's best to tackle concrete problems as soon as you discover them. Repair projects can span a wide range, from sealing a surface to replacing an entire structure. The most common repairs are filling cracks and repairing surface damage. Another solution is resurfacing -- covering an old surface with fresh concrete. A good surface repair can last for many years, but if there is underlying structural damage, it will not be a permanent solution.

-- Tips courtesy of HomeAdvisor.com