6000 psi in 12 HOURS!

[knightwadda]

I need some ideas to run a trial on trying to obtain a 6000 psi in 12 hours mix. I need 5" +/- 1" slump and i am planning on using polarset, adva 120 and around +/-1000 lbs of cement. Any thoughts?

 

[Ron]

What other properties do you need? (durability, abrasion, shrinkage control, etc.)

What coarse aggregate are you using and what nominal size do you contemplate?

What is your placement method?

 

[knightwadda]

The properties do not matter.
I am going to use pea rock (# 89)
placement is going to utilize a pump, because it is about 40' from ground level.

 

[Ron]

Well, yes the properties do matter. Keep in mind that concrete that gains strength that fast will also produce a high heat of hydration, so cracking and other heat-gain considerations must be made.

Consider using a high-early strength cement (in the US, that's Type III cement). If you can't get that, consider a high-early strength admixture, a low water-cement ratio, a high-range water reducing admixture, and air entrainment.

With the proportion of cement you've noted, you'll get high strength, but 12 hours is a bit ambitious for a 6000 psi mix. You at least have a reasonable place to start though, with the cement content and admixtures you've noted.

 

[civilperson]

A heated form for the concrete mix can get you 50-75% of the ultimate strength in the first 18 hours. Try a 8400 psi or better design mix warmed to 160 degree max(f) at 20 degree/hour increase from the initial set temperature.

 

[knightwadda]

Civilperson i love the heat treatment idea, but can't use it for this project, but will keep that one in my back pocket for future reference.

Well my first trial yielded 4670 PSI in 12 hrs, 5850 PSI in 14 hrs and by the 15th hour i got 6670 PSI. So i'm not too far off, i increased the admixtures a bit and am waiting on the 12 hour mark to see where I'm at. I'll keep you guys informed. Thanks to everyone for their input.

 

[BigH]

It would be kind of interesting to know what the project is. High rise construction?

 

[knightwadda]

I have no idea what the project is for.

 

[Ron]

knightwadda...if you don't know what the project is or the end use of the concrete, then I would suggest that you qualify the hell out of your report for liability purposes. Not knowing anything about the project can get you into some problems with liability if anything goes wrong.

 

[concretemasonry]

Mix design is one thing, but curing is the challenge.

Site operations can be problematic and often no avoidable.

Plant production is generally limited by materials and to a lesser extent.

I have seen hollow concrete block batched, mixed, molded, cured and placed on delivery pallets that tested 8700 psi in 8 hours after batching. - All due to curing (360 F)and controls. - Slightly higher strengths may be possible, but there is no need to produce them for current designs.

Concrete panels and tees can be made at high strengths (not that high) at lower strengths due to the controls and accelerated curing at elevated temperatures under controlled conditions.

The problem is how to specify and control the conditions for a specific project, site and conditions after the placement is guaranteed. If it is not placed properly there could be little correlation between the test cylinders and actual results.

I admire the testing facility that is able to cap and test sets of cylinders on an hourly basis, since that is a lot of time involved and there could be some overlap on the timing.


Engineer and international traveler interested in construction techniques, problems and proper design.

 

[knightwadda]

I understand the problems that might face this job during placement, and i believe the engineer asking for this type of mix must know what he or she is going to need done right, in order to achieve the desired final produce.
If you ask me i do not think this job is worth the hassel. They are only ordering 10 yards, but because they know the CEO of my company directly and I am therefore forced to deliver this mix with less than a weeks notice lol.
I intend to caution the company regarding proper curing of this concrete before we pour.
As mentioned before heat treatment curing would have helped out a lot, so i will try and contact the engineer on this project directly and get better infor.
Thanks again to all.

 

[concretemasonry]

For a small job forget about a plant produced product, since the scale of things does not require the sophistication.

That job is only one load of concrete, which is minor compared to the forming, pumping, placing, finishing and curing costs, let alone the costs of inspection and testing. The testing/verification and mix design is more than the cost of almost everything else.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[knightwadda]

Thats excatly what i told the sales manager, the time i've invested in this mix does not warrant 10 yards of concrete. But it's beyond my control so, all that matters is i get it done. Am at 5500 PSI so am hoping my last batch does the job.

 

[beton1]

Curious to find out what the concrete ultimately ends up being used for and your success with the strength requirement. Can you not use something larger than pea gravel (is this a small pump?) as shrinkage and creep will be issues. You need to know how long forms will remain...
Enough said by others.

 

[knightwadda]

I got 7500 PSI yesterday, the concrete looks good shrinkage wasn't a problem and am set to pour tomorrow morning. I'll let you know how it goes. Thanks again gentlemen