New driveway - how long to keep concrete wet?


I finally got my new driveway poured. Question: Should I let it dry out, and if not, how long should I keep it wet? I've been going out several times a day and hosing it off to keep it wet. It's not hot, but the wind is blowing and the sun is shining, and it drys out after a few hours. At what point do I stop and just let it dry?
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The first 3 days are the most critical. If you had a way to cover it with visqueen or set a lawn sprinkler to run continuously, your task would be easier. ______________________________ Keep the whole world singing . . . . DanG (remove the sevens) snipped-for-privacy@7cox.net
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"Ook" <Ook Don't send me any freakin' spam at zootal dot com delete the Don't send me any freakin' spam> wrote in message

Thousands of yard of concrete are poured every day and allowed to dry. The few hours your dried will make little difference. The longer you can keep it wet the better though, as it will cure stronger. A week would be great, but a few days will be sufficient.
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In my case, the cement company had electrical problems, so they could only send one truck. My driveway is done, but the sidewalk in front of it probably won't get poured for a few more weeks. This driveway will not see vehicle traffic for a month, and it will rain on it most of that time.
I've seen a lot of concrete where the top has eroded over the years due to rain. My old driveway was badly eroded, and there are sidewalks all over the neighborhood that are in bad shape because the top has eroded. Is that because the outer layer dried before it could setup hard, or is that just what happens over time to concrete?
I guess what I'm really after is, what is the difference between a few days, a week, and a few weeks? I'd love to see a hardness or strength versus time kept wet curve.
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"Ook" <Ook Don't send me any freakin' spam at zootal dot com delete the Don't send me any freakin' spam> wrote in message

Results of Proper Curing
More Durable Concrete: Good concrete, properly cured, has fewer pores and crevices where water can enter, freeze, expand and crack the concrete. Air entrainment helps make more durable concrete, but its use must also be accompanied by proper curing.
More Wear-Resistant Concrete: Well cured concrete (28 day curing period) will develop a surface twice as wear resistant as a surface that is cured for only three days. Proper curing prevents dusting and means less cracking, crazing and spalling of the concrete. All in all, the better the curing, the better the concrete.
http://www.concretenetwork.com/concrete/slabs/watercure.htm
After concrete is placed, the concrete increases in strength very quickly for a period of 3-7 days. Concrete which is moist cured for 7 days is about 50% stronger than uncured concrete.
Water curing can be done after the slab pour by building dams with soil around the house and flooding the slab. The enclosed area is continually flooded with water. Ideally, the slab could be water cured for 7 days. Some builders on a tight schedule water cure for 3 days as this achieves approximately 80% of the benefit of water curing for 7 days.
Consider planning your job to pour at the end of the week, build berms, then flood over the weekend. You get he benefit of water curing without losing too much time in the schedule.
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This idea only works on flatwork that is level as in floors. A driveway dropping 5' or 5" doesn't lend itself to flooding.
Rain and water do not erode concrete unless you have acid rain in your area or subject the concrete to sulphite attack. Wind, freezing within the first 3 days, too hot without curing, and overfinishing/jitterbugging can all cause the top to delaminate. Salt can be deadly. Failure to use air entrained concrete in a climate that has freezing temperatures will lead to freeze/thaw damage.
Hopefully you used low water/cement ratio mix, 3000 or 3500 # air entrained concrete, properly cured that was poured on a well prepared sub grade that has more than enough contraction joints tooled or cut into the concrete. No concrete over 12' in any direction without a joint!
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On Sun, 18 Mar 2007 14:57:26 -0700, "Ook" <Ook Don't send me any freakin' spam at zootal dot com delete the Don't send me any freakin' spam> wrote:

week.
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Ook wrote:

Concrete does not dry hard, it cures. The problem that happens is when it does dry before it cures. Water is part of the cured concrete.
What you want to do is to keep the surface area from going too dry during the initial cure period. Most people will suggest that three days is good and that is a good starting point. If it dries out sooner the surface will be less strong. It you can keep it from drying (it need not be wet) longer is better. In some applications it takes years to reach full strength.
Commercially they often spray on a paint like material to retard evaporation or use plastic.
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On Mon, 19 Mar 2007 07:41:56 -0400, "Joseph Meehan"

They told me in 1971 that the locks of the Panama Canal were still getting harder after about 70 years.

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mm wrote:

Same with Hover dam. They built in water pipes to cool it as the curing operation is exothermic.

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