When there's an unsightly concrete driveway, everyone would like some way to 'cure' the problem, but that's not what we mean by curing concrete.  It is true, however, that had the problem concrete been properly cured, it may never have gotten sick.

Curing is the maintaining of a satisfactory moisture content and temperature in concrete for a sufficient period of time during its early stages so that its desired properties may develop.

The amount of water in the concrete while it is being placed is normally more than must be retained for curing. However, concrete that dries out too quickly may not retain enough water needed for the hardening process - a chemical reaction called hydration.

Temperature also greatly affects the hydration process.  While hot weather can make the concrete harden and gain strength faster, it ultimately leads to a weaker concrete than one that has been kept cool (but not within freezing range) during its first few days.

Thus, the goal in curing is to keep the concrete cool and moist so that it gains its strength slowly, but efficiently.  Laboratory tests show that moist cured concrete can be twice as strong as concrete cured in a dry environment. 

Curing can also help concrete to be more durable, meaning resistant to damage caused by freezing and thawing.  As long as the hydration process continues in concrete, the cement portion hardens and becomes more dense.  If concrete is properly cured, it will be less porous than uncured concrete thus making it more difficult for water and salts to penetrate.

Properly cured concrete is also more wear resistant and less susceptible to dusting and scaling.

There are numerous methods for curing concrete from covering with plastic sheeting or wet burlap to the use of straw or ponded water.

Moist Curing
Probably the best method for curing concrete is to flood the surface continuously with water for the first seven (7) days after placement.  However, it is important that the concrete not be allowed to dry out. Often, contractors will recommend to the homeowner to wet the new driveway for the first week after its completion.  But, if the concrete is allowed to dry between soakings, this alternate wetting and drying may actually damage the concrete. So if you are going to water cure, plan on keeping the sprinkler going for at least a week.

Membrane Curing
The most common method of curing new concrete driveways is the use of a liquid membrane-forming compound normally called a curing compound or a 'cure and seal'.  These materials are usually sprayed or rolled on the concrete surface.  Once dry, they form a thin film like varnish on wood which restricts the evaporation of moisture from the concrete.

The most important thing to remember regarding the use of a curing compound is timing.  The application of these products should be done as soon as the final finishing operations are complete or as soon as their application won't mar the concrete's surface.  So if someone says, "Lets wait until tomorrow," you will know it's not a good idea.

The next most important thing is application rate.  A light sprinkling or dusting on the surface will not do the trick.  A sufficient coat according to the manufacturer's recommended coverage rate is critical.

Curing with sealing in mind
When choosing the curing method and materials that will be used on your driveway, one important aspect to consider is how you intend to seal and maintain your concrete in the future.  Sealing your concrete is addressed under Sealing, for now lets look at how the curing method can affect your sealing decision.

The most common type of membrane cure used is referred to as a 'cure and seal.'  But let's make one thing clear, this is not a one step process for permanent concrete sealing.  It does, however dictate the use of a film-forming sealer unless the 'cure and seal' is chemically removed or sand blasted away.

If you plan to use a penetrating sealer for ongoing maintenance, then your concrete should  either be moist cured or cured with an easily removed concrete curing compound.

By making the sealing choice before the driveway is installed, you can then inform your contractor on the curing method that you would prefer.