"JJ" wrote in message
. ..
Almost two weeks ago I had 3,100 sq ft of concrete poured for a driveway
and apron in front of the garage. I was told to let it cure for 7-10 days
before driving on it. We gave it 9 days before pulling one car into the
garage.
13 days after pouring, I've noticed I have 3 major cracks in 3 separate
sections. The cracks run right through the expansion joints, from one
side to the other of the drive and are spaced about 20ft apart. They are
about 100ft from the garage and apron sections.
The contractor is coming over this week to check it out and I'm wondering
what demands I can make to cure this? He has not been paid yet!
What are my reasonable options to fix this?
Thanks,
It's refreshing to see someone actually blaming something else for cracks in
concrete rather than the ready-mix folks. I spent 20 years running a
multi-plant ready mix business, and this was one of the biggest headaches I
had to contend with. For some reason, people in this area blame the quality
of the concrete itself for any cracks that occur, even when the concrete is
poured on soft ground in hot weather with no curing and no joints.
You didn't mention the area you live in, but during this time of year,
positive curing is usually necessary because of the rapid drying that will
occur in hot weather. When concrete dries out, it no longer gains strength.
"Curing" is not simply leaving it alone for a certain period of time, but is
maintaining adequate moisture in the concrete for hydration to continue
taking place. Curing can be by use of a spray-on curing compound or using
sprinklers. Plastic sheeting also works, but discolors the concrete. When
concrete isn't properly cured, it tends to be weaker and crack more easily.
When cured properly, it develops the strength it was designed to have.
As for the cracking of the concrete, you're probably going to see more of it
than what you have right now. If you have 4-inch concrete, it tends to
crack every 10 to 15 feet over time. Ideally, contraction joints should be
sawed or tooled every 10 feet to relieve the stresses from expansion and
contraction. The cracks will then occur in straight lines that are less
objectionable. This is rarely done properly in residential concrete.
What you got in your driveway and apron is probably not uncommon in your
area. Contractors tend to do what everyone else is doing (and what they've
always done), and they have to be forced into doing it any differently. I
tried for years to get contractors to put in more joints, but was almost
completely unsuccessful in doing it. I also made a concerted effort to
promote positive curing of the concrete. I had a little success with
curing, but the vast majority of residential concrete in this area is still
not cured properly.
The cracks you describe as "major" are a cosmetic problem, not a structural
problem. Cracking is a normal part of the concreting process and is to be
expected. We can expect them and work with them by putting in sawed or
tooled joints and curing the concrete to help minimize cracking, or we can
just pour and let the concrete crack as it wants to. Either way, the
cracking will occur, and an unplanned crack is no more harmful structurally
than a planned crack.
I've tried several different ways to fix cracks that had occurred, but none
of them worked satisfactorily. Demanding that the contractor tear it out
and re-pour it is excessive since the utility of the drive and apron hasn't
been compromised. Years ago, homeowners were just happy to have a hard
surface to drive on. These days, our expectations are much higher, and we
expect that the concrete will be an attractive addition to our landscape.
If you need to research this problem on your own, a good resource is
http://www.concrete.com/Forum/Forum.htm There are also many other sources
of information about concrete on the net.
Best wishes,
David