Question For TAB

[billt]

TAB, you know concrete and construction, so I want your opinion on this. Yesterday I had my driveway widened. The whole pour was around 8 yards total. The guy said the stuff he poured was 3,500 PSI concrete. (The receipt from the concrete outfit confirmed this). They started pouring around 7:00 AM. The concrete truck pulled away and left from my house around 8:30 AM yesterday morning. It was cloudy and around 74 degrees. The humidity was 25%.

The crew did a real nice job finishing it. And they pulled the forms, cleaned and packed up, and left around 11:00 AM. Around 4:30 PM we got a light sprinkle of rain. Just enough to barely wet the concrete. Overnight we got a few more sprinkles. All total not even a 1/10th of an inch of rain total. This morning the new poured concrete was wet to the touch, and seemed hard. I don't know $h!t about concrete. Do I have anything to worry about?

[Timothy]

Concrete doesn’t dry, it cures! 

Keeping it wet helps harden the cure.

[billt]

Concrete doesn’t dry, it cures! 

Keeping it wet helps harden the cure.

That's what I've read. I know when I had my pool put in, they told me to keep misting it down with the hose, and not let it get too dry. I asked about it puddling up at the bottom, and they said it won't hurt it at all. That was 20 years ago and my pool is still like new. But I don't know if it's the same type of concrete that they used in my driveway? I think it had to be much stiffer.

It just scares me to see water on it so soon after it was poured. But as I said, I don't know $h!t about concrete.

[Timothy]

I’m guessing there’s probably a dozen different concrete types.

Water evaporates from the mix after the pour, keeping it covered and damp helps.  I’m surprised the company didn’t give you some advice on how to allow the pour to cure properly.  I did a large patch in the driveway some years back and it was 8 to 10 inches thick in the area that I corrected. It took about 7 to 8 days to cure properly.

[billt]

They told me it would reach 75% "strength" in about 3 days. And not to park any vehicles on it for about a week. From what I've read, it takes around 30 days or more to cure to 100% "strength". I don't know.

Right before they left they sprayed a white, milky looking, water soluble "curing agent / sealer" on it. That all dried before it started to sprinkle. I just went out and looked it over real good, and it seems to be setting up nicely.

[Sponsor]

[crusader rabbit]

If concrete is kept moist, it will continue to cure for up to a year.  That doesn't mean it isn't ready for use long before the year is up.  Just that it will continue to get harder over time. 

Drying it more rapidly actually inhibits the curing process.  After the first couple of days, even large quantities of rain should have little to no impact on your pour and will actually prove beneficial to the long term strength.

Crusader Rabbit

[billt]

Thanks. You guys are telling me what I want to hear. The clouds are breaking up, and the Sun is out. It's supposed to be sunny and in the low 80's until Thursday. Then we're supposed to get a little more rain.

[TAB]

It getting wet was a good thing, it slows down the curing process.  It never stops curing.  With out getting super technical, it reacts with co2 in the air in a exothermal (produces heat) chemical reaction.

[billt]

Thanks TAB.

[Big Frank]

Most people say that it reaches it's full strength in 28 days, but should be at 75% strength in 7 days. TAB is right about the curing never stopping. The concrete in the Hoover Dam is still curing. The process starts out fast but constantly slows down.