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RE: More Concrete[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: <seaint(--nospam--at)seaint.org>
- Subject: RE: More Concrete
- From: Harold Sprague <spraguehope(--nospam--at)hotmail.com>
- Date: Thu, 23 Dec 2010 06:13:34 +0000
Adva is a good choice because it not only acts as a great high range water reducer, but after the concrete is placed it sets faster. That will let you get on it faster for finishing. And will let you protect it more quickly. |
The rebar placement will make screeding more of a challenge. I would urge you to look at the Copperhead Laser screed.
Regards, Harold Sprague
Subject: Re: More Concrete
Date: Mon, 20 Dec 2010 12:27:39 -0500
You must have done this a lot. Thank you for the advice.
One thing that slightly work to our advantage is the fact that the area of pour is much less than 20,000 sq. ft. we are pouring the slab, the grade beams, pile caps. The slab is an average of 13" to 14" thick. They are planning to pour this in the first week of January. The weather is going to be cool, however, we do have a concern with rain!
Farzin S. Rahbar, SE
David C. Weiss Structural Engineer & Associates, Inc.
(818) 227-8040 Ex. 13 Fax: (818) 227-8041
From: Rick Stone <rstone(--nospam--at)madisonconcrete.com>
Sent: Mon, Dec 20, 2010 5:57 am
Subject: RE: More Concrete
Some good advice from the list. Sounds like you are trying to pour about 20,000 sf of 8 inch slab? My two cents: 1. Pumping can run at about 80 CY an hour max---so that means a truck every 7 minutes or so---make sure the batch plant has the trucks to do that!! Also, it may take more than that to batch each load!! Make sure you discuss the rate of delivery needed to attain the goal. At 80 CY an hr you'll be there a long, long time--that is 6 hrs plus just to get it in, and then the finishing may take another 6 to 7 hours.....lots of overtime. Costly. And if you drop to 40-50 CY/hr, you will be there a really, really, long, long time. Quality of finish drops when the crews are exhausted, cold, hot, hungry, tired....We plan and attain 80 CY/hr pump rate almost all the time....to minimize fatigue. 2. Short-batching can work but planning and control are key. More below.... 3. If it is cool or cold ambient in the area that you are pouring in, the 90 minutes may be relaxed....I know this is anathema to a lot of designers, but it works. 4. If the slab needs to do decent numbers (Ff/Fl) the finishing gang will not want any interruptions in service or changes in consistency until perhaps the last 20% of the slab. Consider accelerator in the last loads to let the finishing proceed efficiently. If you start in the morning when it is cold, the trucks and equipment are cold (or at least, not hot from use) and the concrete will take longer to have an initial set; as the day goes on the ambient climbs, equipment gets warmer (trucks) and the set rate will pick up--try to finish with a bang, consider accelerator. 5. Again, the steady delivery is what is needed. If there is a traffic issue, or if it is taking longer to adjust loads upon arrival, delays may result; make sure that you remove as many of the rocks in the road as you can, plan the whole deal, then work the plan. 6. That said, site trimming loads can take time, lead to excessive discussion and thus delay. IMHO, do not short batch, relax on the 90 minutes, but make sure that the plan is sound (delivery rates, etc) and that the plant and field crews have considered all the what-ifs....... 7. HRWR is a must for the strength you are using. A Shilstone-style aggregate gradation may be difficult to attain in some markets (like ours, we have crappy course runs) but it can work. Make sure that the finishers use an evaporation retarder (E-Con, for example) and at 5000 psi, Harold mentioned the lack of bleed water. Our experience with the Polycarboxylates at 5000 psi/7-8 in slump is that it strikes off easily, and finishes with some but not a lot of bleeding. 8. Test pours are considered by some specifiers to be a great idea BUT.....in our experience, they NEVER replicate what actually happens in the field. A test pour of 20 yards, done in an hour, in no way resembles a large undertaking like a 500 CY pour because after 6 hours, men are tired-their work rate and quality decrease--, weather can change, materials will vary in consistency and temperature.... IMHO it is a waste of time, resources, and money. We routinely do 500 CY decks and slab on grade and have great success with quality and finish---but we plan, plan, and plan again, check the plan, then work that plan. Work it really hard. Good luck!!! ------------------------------------------------------------------------ -- 3 Message:0003 3 ------------------------------------------------------------------------ -- From: Harold Sprague <spraguehope(--nospam--at)hotmail.com> To: <seaint(--nospam--at)seaint.org> Subject: RE: More Concrete --_a7e41168-40de-4b7d-ac4f-9ea206e7fd92_ Content-Type: text/plain; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable Farzin=2C Tom gave you some excellent advice. I would offer some more considerations= . =20 =20 1. Have the admixture technical reps buy into the process. =20 2. Have a preconstruction meeting with all of the stake holders attending = (concrete producer=2C admixture manufacturer=2C pumper=2C finishing contrac= tor=2C GC=2C testing lab=2C etc.) to buy into the process. If you use an o= verhead pump=2C the concrete you get at the maximum reach will not be the s= ame concrete as they raise the boom to its maximum height (close to the tru= ck). For placing=2C I prefer 1. Tailgating if you can=3B 2. Mini-conveyor= =3B 3. Bucket=3B 4. Georgia buggy=3B 5. Horizontal line pump (slick line= )=3B 6. Overhead pump=3B in that order. The method of placement selected w= ill have an impact on the mix. Even the screed that you use will have an i= mpact. I prefer the Copperhead laser screed. I prefer the polycarboxolate= high range water reducers=2C and I prefer a uniformly graded aggregate (Ji= m Shilstone lesson). The polycarb high range mix is a bit different to fin= ish. It is not hard=2C but there will not be the bleed water to which most= finishers are accustomed. =20 =20 3. Do a test pour with all of the entities and replicate the field conditi= ons. =20 =20 4. Plan for the worst (break downs=2C traffic tie ups=2C etc.). =20 Regards=2C Harold Sprague ******* ****** ******* ******** ******* ******* ******* *** * Read list FAQ at: http://www.seaint.org/list_FAQ.asp * * This email was sent to you via Structural Engineers * Association of Southern California (SEAOSC) server. To * subscribe (no fee) or UnSubscribe, please go to: * * http://www.seaint.org/sealist1.asp * * Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you * send to the list is public domain and may be re-posted * without your permission. Make sure you visit our web * site at: http://www.seaint.org ******* ****** ****** ****** ******* ****** ****** ********
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