Expert: Roger Zona - 6/25/2010

Question
QUESTION: A new home is being built for us in Georgetown, Texas. Last Friday the drive and walk ways were poured.  When we looked at the concrete on Saturday there were spots on most of it that look like it had rained and in some areas like the rain ran.  There are some places where there are no spots. Since Saturday none of the spots seem to have disappeared.

In a couple of places we dug into the spots.  When this is done it seems to change to a small hole.

We have discussed with the contractor and he said it just needs to bleach out.  

This is a new area with many homes being build and finished.  We have looked at other concrete work and have not seen anything like this on them.  The builder is very reputable.

With this information can you give an opinion on what we have.

ANSWER: Hello William,

Please excuse my delay in responding.  I had a death in the family and had to fly to Michigan.

Your contractor's comment about "bleach out" has nothing to do with concrete.  If he had said it needs to cure longer, I could buy that.

New concrete reacts to several conditions.  Too much water that is slow to evaporate; to little water and it dries to quickly; over toweling and the aggregate rises to the surface; and weather conditions such as rain, or hail; improper curing time; and wrong design mixture.  I recommend 3000psi concrete  (2500psi minimum)for drives and exterior pours. And always mesh or rebar reinforcing.
If properly mixed and installed, concrete should be a uniform color on the entire surface.  Concrete should dry and cure for three days before walking on the surface and up to 21 days to get to full design strength and when a car can drive on it.

I would expect the contractor to replace and re-pour the driveway if the blotching did not go away.  You might ask your local building department by what standard do they accept a concrete pour.

I hope this has been helpful.

Roger
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---------- FOLLOW-UP ----------

QUESTION: Thank you for the response.  I have a followup question.  

Many walks and driveways in this area have been coated with various types of coating.  The house next to us has it in his garage and on his front walk and driveway and it is very nice looking.  It has been down for some 4 years and still looks good.

How would you feel about having this done to the concrete I described to you? They have asked that we give it some time to see what happens.  We are scheduled to close on about 7/15.  My thoughts are to set a time limit and if it is still spotted after something like 60 or 90 days, then they pay for the coating that we select.

In an e-mail the builder said they and the concrete contractor, both of which are large in the area with good reputations, would stand behind it.

Answer
Hi William,

Back home again and again I apologize for the delay in my response.

There are several concrete "coatings".  I like a concrete stain.  It comes in many colors, is easy to apply and covers up a lot of ills.

I suggest you drive around and spot a drive that appeals to you - knock on the door and ask what system did they use on their drive.  The owner will be flattered that you think they have good taste!

As for the email - save a copy.  It's a "contract" commitment.  If the builder is willing to re-place the drive you should have that agreement in writing.  I suggest, that at the closing, you escrow enough funds to cover the cost of re-placement or re-surfacing (coating) until the work is completed.  In my area, concrete drives and walks cost about $3.50 per square foot.  A drive 40'x 16'= $2,2400.00.  Your area may be higher or lower.  

Good luck

Roger
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