shrinkage cracks ... how bad do they get ?

[gjbuilder]

Well, here's the forum post I hoped never to make.

We poured a 50x60' pad, 6" thick, under our pole barn. I did TONS of research about the makeup of the pad ... the rebar, the mix, the chairs, etc.

But I didn't really understand the curing.

As soon as the pad was poured I asked my concrete contractor (I hired out this job to pros - did none of it myself) what to do about watering it, and he said just wet it done 3-4 times per day.

So that's what we did - we dutifully watered down the whole pad 3-4 times every day for a few weeks. Of course most of the pad dried every day between waterings, but I didn't know how bad that was.

So now we have shrinkage (discontinuous) cracks in almost every section of the pad.

My question:

I really only see these because I am looking for them / sensitive to them ... they're really not that visible or noticeable. Do they get worse ? Do they get bigger over time ?

It seems like once the shrink has shrunk, that's it, and there's no reason for them to get bigger ...

I'm just wondering how bad this problem gets over the years ....


(the pad was laid at the end of January, low temps, cloudy days, even a bit of rain here and there after the pour ... and now it is mid-July and I have seen these cracks develop over the last 2 months)

 

[06 DIESEL]

Was the ground frozen or below 40* when you poured the concrete? Did you put concrete blankets over the concrete if the ambient temperature was going to or got below 40* before 7 says?

 

[gjbuilder]

Was the ground frozen or below 40* when you poured the concrete? Did you put concrete blankets over the concrete if the ambient temperature was going to or got below 40* before 7 says?

Northern california. Temps were 55-70 during the day and 50-55 at night.

Ground was not frozen.

 

[Radix2]

You did much more than 90% of people do to cure a slab, you are not responsible for the shrinkage, it is the nature of the beast. There is no watering method that will prevent the shrinkage in the end - the extra moisture can just slow the process so that there might be more strength when it happens.


I doubt you will get much change from shrinkage at least in the future - most of it is that with water and dirt, you may see more than before.

 

[gjbuilder]

You did much more than 90% of people do to cure a slab, you are not responsible for the shrinkage, it is the nature of the beast. There is no watering method that will prevent the shrinkage in the end - the extra moisture can just slow the process so that there might be more strength when it happens.


I doubt you will get much change from shrinkage at least in the future - most of it is that with water and dirt, you may see more than before.

Hmmm....

The control joints (tooled) that were put in were in 12x12 and 6x12 sections, so these were not that large of "uncontrolled" surface - should have been sufficient control joints.

I think that if I had kept it wet continuously, with sprinklers, for the first week ... or maybe even 3-4 days ... I would have avoided these cracks. The biggest, longest crack is in the section just inside the large barn doors where the sun shines in - so that always dried first and fastest every day after we watered it. I don't think that's a coincidence.

Anyway, I'm glad to hear you think shrinkage cracks don't get any bigger - curious if anyone else will weigh in.

Thanks.