Concrete setting time

Rondo84

Hi I was wondering if anyone can help me,
I'm pouring a slab of 20mpa concrete and I'm not sure how long I will need for it to set enough to have medium to heavy traffic on it!!

Lattimer

Depends.

Talk to your supplier. Concrete can be ready for traffic in 45 minutes, or after 2 weeks of wet curing. It all depends on the mix.

dave54

Of course it all depends on moisture and temperature, but the rule of thumb if that you can walk on the concrete after 24 hours; it will gain around 2/3 of it's full strength in a week and another 2/3 after 4 weeks total curing time. It will actually keep on curing and gaining strength for many years. It's typical to allow foundations to cure at least 3 days before framing on them. Also, note that curing time is extended around 1/3 for every 10 degree drop in temperature, with the optimum temp at between 65F and 80F.

concretemasonry

Keep in mind that the rate of curing depends on the temperature of the concrete and not the air temperature.

Dick

Bud Cline

concretemasonry

Bud is right -

Concrete itself will gain heat from the curing (heat of hydration, technically) that keeps the concrete temperature up for curing. What you do to maintain the heat is up to you (poly, blankets, sun exposure, etc.), but for that strength of concrete, whatever is done in a reasonable climate will be enough.

In most cooler climates, at this time of the year, heated concrete is normal or available at minimal cost to provide the "jump-start" that precludes the minor cost inconveniences.

Dick

woodworkbykirk

so its at 4/6 of full strenght between the end of the first week up to the start of the 4th week? when does it get to 5/6 ????


if its for a slab you can walk on it after about 24 -30 hrs.. but dont drop anything on it its not fully cured. concrete reaches near full strenght after 28 days in optimal conditions

Daniel Holzman

Concrete strength is generally quoted based on 28 day cure, so for example 3000 psi concrete (English units) is designed to reach 3000 psi after 28 days, however after several years the concrete may well reach 5000 psi or even higher. Early cure mixtures use special chemicals to accelerate curing, and can reach 50 percent of 28 day strength in as little as 8 hours. Unless you know the specifics of your mix, you should be conservative in assumptions about strength after less than 28 days.

Msradell

Yes, Dave's statement is correct the second 2/3 is an approximation of how much of the remaining strength will be obtained. Thus 2/3 of the total in the first week in and 2/3 of the remaining 1/3 in the next three weeks. So an approximation of the strength after four weeks is 8/9 of the ultimate strength. Of course as stated before the mix makes a big difference.

dave54

Thanks for the clarification, Msradell. I was referring to 2/3 of the remaining 1/3, in weeks 2, 3 and 4, which for all intend and purpose means about 90% of full strength in 28 days.