I've been told that wetting concrete as it dries is valueable in hot, dry weather to keep it from drying too fast. If yours was poured in cool, humid weather, then maybe it wouldn't have been very helpful. On the other hand...

The best way to cure concrete is to keep it moist for 30 days. This helps eliminate cracks by limiting rapid shrinkage, and by keeping it moist it will cure better resulting in a stronger finished product. While cool moist temperatures do help, because it will not dry out as fast, that is not enough.

Common ways of keeping it moist while curing are:
1. Cover the concrete immediately after finishing with a plastic sheet to hold the moisture in. Keep it covered as long as 30 days for best results.
2. Use a sprayed or rolled on curing compound immediately after finishing. This is a clear or white resin that is applied to the concrete and will hold the moisture in until it is completely cured. Some curing compounds are made to dissipate over time while others remain intact.
3. Use a soaker hose that produces a fine spray of water over the concrete and keep it wet.

While many people do not maintain the moisture for the full 30 days, it is better to do so. (Longer the better.)

Hey GlennG,
Now that we know what's best, can you give us an idea what's usual and customary?
As you said, 30 days is a long time to keep concrete wet.

..and also, should I consider my contractor inexperienced or negligent since he did not do or advise to do ANY of what you mentioned, GlenG?

Thanks,
Jason Alden
SW Florida

For exterior concrete the most used methods of curing are by applying a curing compound or use of a soaker hose. If using a curing compound, the dissipating type is best for areas that are prone to get slippery when wet.

For interior floor slabs, covering them with plastic sheeting (4 or 6-mil polyethylene) is preferred. It works better at retaining the moisture and will not leave behind any residue that could affect the adhesives used to install the floor coverings.

I would consider your contractor negligent if he did not use any type of moisture retention. (Especially so if the temperature was near or above 80 degrees.) Unfortunately there are many contractors that either don’t know or just don’t care. Driveways and sidewalks seem to get poured and forgotten about, mainly because there are no structures being supported by them and thus little or no inspections they have to pass.

Thanks, your information is very helpful. Just for the record, what could happen to concrete that hasn't been cured by any of the mentions you have mentioned?

Thanks again,
Jason Alden
SW Florida

Since the concrete was poured 10 months ago most of what can happen already has. The concrete will shrink too fast early on causing stress cracks and will not be as strong as it would have been had been cured properly. If you are going to have any problems with it, it should already be apparent.

Glenn,

Thanks for the information.

I do want to add that the contractor cut grooves in the concrete in order to help control cracking. Would this replace the need to cure using one of the methods you mentioned?

Yes, I had stress cracks develop literally months after the concrete was poured.

I feel that my contractor was negligent and I am considering to persue some sort of restitution. I have not yet contacted him about this.

We spent $7,000 on a circular driveway and am now questioning why we have cracks and why the contractor did not cure it properly.

Thanks,
Jason Alden
SW Florida

Many contractors do not follow the recommended procedures when pouring driveways and sidewalks. Sawing the “control joints” in a concrete drive should be done as soon as possible after the pour is completed or they should have been tooled into the fresh concrete before it set up. If the control joints are not in place within the first 24 hours the concrete will likely have already started to crack on it’s own even if you cannot see the cracks yet. Control joints should be placed every 10’-15’ max. These joints allow the concrete to crack in a straight line where you want it to crack.

Expansion joints should also be used. They are placed every 30-40 lineal feet min. Expansion joints are made of a compressible filler strip (Usually made of asphalt impregnated fiberboard) the full depth and width of the concrete and ½” thick. These are made to compress when the concrete expands in hot weather preventing compression cracks. Expansion joints should also be left slightly lower than the concrete surface so a good quality caulking can be applied to seal them.

These joints if used at the proper time would have greatly helped your problem, but if the weather was hot when the concrete was poured there was NO EXCUSE for not maintaining the moisture content. These joints are not an acceptable substitution for good concrete curing practices.