How to Purchase & Care for Your Concrete

Hiring a Quality Contractor

   A good source for information on contractors may be your local ready mixed concrete producer.  Click here to see our list of ready mix concrete forming contractors. Receive bids from at least three contractors and be sure each bid is based on the same specifications, including PSI, curing method and aggregate type.  Also be sure to check references.

Getting the Proper Mix Design

Your local ready mix producer and your contractor will assist you in ensuring that the right concrete mix is ordered.  This mix should include:

    Air-entrainment:  All exterior concrete in our area must be air-entrained. All exterior concrete should have approximately 6% air content in the Wisconsin climate.

    Pounds per square inch (psi):  PSI is a measurement used to describe the compressive strength of concrete. The American Concrete Institute states that a typical Wisconsin drive should be placed with a 4500 psi mix design.

Preparing the Subgrade

All subgrades should be uniform in firmness, grade, and dampness.  The driveway or patio should be sloped away from the home for proper drainage, with a minimum slope of 1/8 inch per foot.  If the driveway will be used by cars only, the slab should be 3 1/2 to 4 inches thick; by both cars and light trucks or SUV's, then the slab should be 4 1/2 to 5 1/2 inches thick.  If in doubt, make the slab thicker.  The flexural strength of a driveway can DOUBLE by going from a 4 inch slab to a 5 inch slab.

Surface Texture

In general, a broom finish for exterior concrete is ideal.  It provides a slip resistant surface and helps ensure the contractor is finishing the slab properly.  A smooth "basement" finish on exterior concrete greatly increases the chance of durability problems and is not recommended.  The surface may also have an exposed aggregate look or be colored and stamped.

Curing is Key

Curing is ensuring that concrete has enough moisture and the proper temperature to chemically react to bring your concrete to full strength.  Be sure that curing is a part of the procedure done by your contractor.  Curing is one of the final, but vital steps to construct a quality concrete driveway.  If a driveway is not cured, you may end up with only 50% of the desired strength at the surface, which may not be strong enough to last through the winter.  There are several methods of curing.  The most common is the application of a compound sprayed onto the surface of the concrete immediately after finishing that prevents the concrete from drying prematurely.

Jointing

Jointing of concrete slabs is critical.  Control joints on a 4 inch driveway should be placed a maximum of 10 to 12 feet apart.  The sections of all slabs need to be as square as possible.  The joints should be 1/4 the depth of concrete.

Patience is a Virtue

Quality contractors understand that placing concrete in hot or cold weather requires different and additional steps than placing concrete in more temperate conditions.  Following these steps is critical.

The homeowner can also assist in ensuring a successful concrete project.  Concrete needs, on average, 5 to 7 days before it should driven on and 28 days to reach a strength where it can withstand the rigors of freezing and thawing.  Be leery of putting in a driveway in late Fall.  If it cannot wait until a more temperate time, expect to pay more for the driveway and be cautious of the contractor who is not charging more.  Also, realize that you, as the homeowner, are increasing the chances of the driveway to fail if you insist on late Fall installation.  Your ready mix producer may be a source of gravel for a temporary drive to last until Spring.

Use a Quality Sealer

Water repellent concrete sealers can help to prevent surface defects from cold weather by keeping water from getting into the concrete slab.  New concrete should dry for 30 days after installation prior to applying a concrete sealer.  Applying a quality concrete sealer helps maximize protection and lengthens the time between applications.  Your local ready mixed concrete producer may be an outstanding source for sealers and for further information.  Some sealers, primarily designed for industrial applications, darken or yellow the concrete.  Be sure to ask if the sealer discolors the concrete, if it is compatible with your curing compound, whether it is U.V. resistant and follow the manufacturer's directions carefully.

Use Caution with Deicers

You would not use a strong caustic soap to clean your wall-to-wall carpet, nor use acid to clean your kitchen fixtures.  In fact, most people are very careful about how they clean and take care of the inside of their home.  While concrete is the most durable product available for your home, proper care is a requirement for long-lasting beauty and wear.

One of the most damaging things to a new concrete surface is the use of deicers - especially the first winter.  Here are a few guidelines:

        Avoid Using Deicers the First Year
Concrete takes a while to reach its full strength.  While some deicers, such as salt, do not chemically react with the concrete, they increase the number of freeze/thaw cycles the concrete must go through.  This has the potential of damaging the concrete until it has reached its maximum strength.

        Use Sand Anytime
One of the few safe materials to use to make the concrete surface skid resistant is plain sand.  This can be purchased at several locations, frequently from your ready mixed concrete producer.  Always put safety before the appearance of your driveway, patio or sidewalk.

        Don't Use Deicers With Ammonium Nitrate or Ammonium Sulphate
NEVER use deicers containing ammonium sulphate or ammonium nitrate.  These chemicals are often packaged and sold as deicers, but they will rapidly disintegrate concrete.  Common garden fertilizers containing these two chemicals, or urea, may cause disintegration as well.

After the first winter, deicing chemicals sodium chloride or calcium chloride may be used sparingly.  Washing off road salt that drips from vehicles is also recommended.

Be cautious of products that claim to "be safe for use on concrete."  Avoid any product the first year and then avoid products using ammonium sulphate or nitrates.