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fast curing &/or high early strength

fast curing &/or high early strength

fast curing &/or high early strength

(OP)
Is it possible to gain 4000 psi (full design strength) from normally cured (wet or membrane cure) concrete in 24 hours?  How practical is this? expensive?  What effect might this have on the durability of the concrete (if any)?

Several methods and products are available for obtaining high early strength.  Of course, for reinforced concrete, no chloride-containing accelerators would be allowed.  The ones to consider include the following (and maybe more?):

Non-corrosive, non-chloride admixture to the concrete mix to speed formation of cement gel and thus, speed the concrete cure rate.

Specialized addition to the cement itself during production (basically a special cement) that provides accelerated reaction.

Using a very high strength concrete such that the strength after 24 hours is only a small portion of the design strength (f'c >> 4000 psi).

What methods/products would be necessary? recommended?

Please also provide any resources you may know of to help in this task.

(I have posted this in the admixture engineering forum as well.)

~dison

RE: fast curing &/or high early strength

Heating the concrete element (usually by steam curing) will increase the rate of strength gain.

We have achieved 20 to 25 MPa (3000 to 3600 psi) concrete in 20 hours on precast beam elements using steam curing and without special admixtures.

The rate of strength gain increases rapidly as the temperature goes from 20 to 50 deg C.  There is no advantage, with most cements, in increasing the temperature above 70 deg C, and at higher temperatures there may be degredation.

A good book on concrete is 'Fultons Concrete Technology' published by the South African Portland Cement Institute ISBN 0 620 09988 7.

RE: fast curing &/or high early strength

And, of course, you could specify Type III cement.  Be careful, however, as the "super rich" mixes have a propensity for shrinkage cracking.  Thermal cracking can also be a problem if your pour is massive.  

RE: fast curing &/or high early strength

(OP)
Thanks for the responses!

RiBeneke:

Steam curing will not be possible as this will be cast-in-place on site and access for providing a steam cure system in the field would be prohibitive.

Jim6758:

What do you mean by "super rich"?

Would it be possible to make this a shrinkage-compensated (or non-shrink) mix also?

The placement will not be massive, but it is in conjunction with precast elements to which I would like to maintain surface contact w/o cracking.  The cast-in-place concrete will be contained on all but one side by precast concrete.

~dison

RE: fast curing &/or high early strength

Have you considered the alumina-based cements.  The have both advantages and disadvantages, and are commonly used for patching concrete floors.  They used to go under the trade name of 'Ciment Fondu'.  I think the main drawbacks are high cost and possibly some corrosion/deterioration related problems.

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