Last October I replaced my asphalt driveway with concrete. After experiencing some very cold weather for several weeks, the driveway has raised up such that the edge of the driveway is at least two inches higher than the garage floor. I assume water has gotten under the driveway and expanded. The contractor compacted the gravel in the sub-base. What must I do to correct this problem and how do I prevent it from happening again?

Concrete driveways can be prone to frost heave because they are a large, inflexible mass. If ice pushes up on one area, the whole thing moves.

Even if the gravel is well-compacted, there may be frost heave. Water in the soil below the gravel (and the slab) freezes. The ice lenses that form push upwards, transferring the forces through the gravel and to the slab. The effects will vary depending on the type of soil and the amount of water in the soil.

Right now, there's not much that can be done. When the ice melts, the pressure will be released, and, with luck, the slab will settle back to its original position. There is often a ratcheting effect, though. The slab may not settle back as far as it was originally. After one winter, this may not be a problem, but after a number of years, the slight raises every year may result in significant permanent movement.

The best way to deal with this is to try to manage water as much as possible. Wherever possible, ensure that surface water is draining away from the driveway (and the foundation wall of the house). Improve lot grading, for example, and make sure that downspouts discharge well away from the driveway. Water pooling on or around the driveway can lead to frost heave problems.

Ironically, snow shoveling can contribute to the problem. While I'm not suggesting that you should leave the driveway covered with snow the whole winter, the removal of the insulating layer of snow allows cold temperatures to penetrate the ground further, resulting in the formation of more ice.