Some interesting facts about concrete and asphalt:

The Hard Truth About Concrete: It's Going to Crack

Concrete: Heavy, strong, durable. So it's guarantee should be cast in stone, right?
Actually, just the opposite. And that can be a point of frustration for homeowners and contractors alike. I would like to share with you many of the reasons for this, since most all homeowners will at one time or another have concrete installed either as a driveway, patio or sidewalks.

The Greater Cleveland Chapter of the National Association of the Remodeling Industry held a seminar on the installation of concrete and why it is usually not warranted by most contractors. Mark Steadman of Collinwood Shale Brick & Supply Co. explained the reasons why and also offered additional information about concrete.

Let's start with the basics. Concrete is made from mixing cement, limestone, sand, water and admixtures at prescribed rates. There are also standards that manufacturers of concrete should abide by from the American Concrete Institute. Independent testing laboratories inspect all concrete plants yearly to insure certain standards are met. These recipes are modified for hot-weather pours and cold-weather pours.

Just like painting, surface preparation is crucial to a good concrete job. For the exterior, say a driveway, you have to start with an acceptable base material that can be compacted. The base must be saturated before the concrete can be poured. Interior preparation is much the same, except a moisture barrier is usually placed beneath the base material.

Concrete is usually delivered to the work site in a workable state. Many contractors add water at the job site to make it easier to push the concrete into corners. Steadman says that is a mistake because it changes the mixture, which was so carefully controlled at the plant.

Once the concrete has been poured, it is usually screened. That is the excess concrete is removed by dragging a long straight board across the tops of the forms. Once the concrete has taken its initial set, the finishing process can begin. Two main types of finishing process can begin. Two main types of finishing are called broom finishing and float finishing. According to Steadman, broom finishing is the best type of finish because float finishing is generally overworked and can lead to a weakening of the surface.

Steadman also recommends that a curing compound be applied during the concrete finishing operation, but not a curing and sealing compound. Steadman says that those are two different tasks and need to be done separately. A sealer is a liquid chemical composition that penetrates the concrete surface to form a barrier. This barrier significantly reduces the amount of water that is absorbed in the surface. The sealer should be applied on all exterior concrete after the concrete has cured for between 28-58 days.

Now the hard truth. Steadman says that all concrete will crack. It is a natural function of concrete. Controlling where the cracks occur is the key. Control joints are cut or trowled into the surface during the finishing process, typically every 10 feet or less. Just like the perforation on a ticket stub, these joints give the concrete a place to crack during expansion and contraction, which won't harm the appearance of the job. However, Steadman adds that there is some abnormal cracking, such as shrinkage cracks, that can generally appear within the first week after placement. A concrete expert can tell the difference.

Aside from cracking, two common problems with concrete are spalling and scaling. According to Steadman, spalling is the term for isolated “pop outs” appearing on the concrete surface. These “pop outs” are caused by either certain materials such as many of the salts or ice melters that we put on the driveway or sidewalk or impurities in the base material working up to the surface. Scaling is the delamination of the finished surface that can be either a small size or can affect an entire block of concrete. Some of the most important questions that we receive from consumers at the NARI office is why don't contractors warrant concrete work and why isn't the product guaranteed? :Steadman's answers that by stating that workmanship and concrete do carry an implied warranty. “As a consumer you should expect the concrete to perform its intended function and to have aesthetic quality for at least two years.”

A poorly done concrete job may require the removal and replacement of the concrete in order to rectify a job. However, Steadman says there are products on the market today that allow concrete repairs to be made that are not only aesthetically pleasing, but also have excellent durability.

Do your homework before you hire a contractor for your next concrete job. You could save yourself a lot of aggravation. You can contact NARI, the Better Business Bureau, or even a concrete supplier for references. Although there is no guarantee, the odds of getting a professional concrete installation job will be increased once you have researched the company you hire.