Use of concretes that can do without vibrators?Any warning?
Use of concretes that can do without vibrators?Any warning?
(OP)
Dear Pals
I am in a situation where I have to use fresh concrete without using having to use vibrators because of too much reinforcement in the design
A dealer has suggested a special mix of concrete already certified for this use.
Being a new product to me, I have to ask you if you know of any bad side of this product
respects
ijr
I am in a situation where I have to use fresh concrete without using having to use vibrators because of too much reinforcement in the design
A dealer has suggested a special mix of concrete already certified for this use.
Being a new product to me, I have to ask you if you know of any bad side of this product
respects
ijr





RE: Use of concretes that can do without vibrators?Any warning?
If it is the same type of thing you are proposing to use I would be concerned whether my shuttering was watertight enough to retain the water cement mixture and not just leave aggregate in the shutter. I also remember this stuff reached a very high compressive strength when cured. The link below might also be of some interest.
http://www.concretecentre.com/main.asp?page=609
RE: Use of concretes that can do without vibrators?Any warning?
RE: Use of concretes that can do without vibrators?Any warning?
RE: Use of concretes that can do without vibrators?Any warning?
B. smaller "pencil virbrators" are available for rent. theyare smaller than standard vibrators. I have never used them, but external vibrators may be an option. They attach to and bang on the sides of the forms. They bang the living bejeepers (that's a technical term) out of the forms, so they have to beconsiderablly heavier than internally vibrated forms.
C. Since the bars are tight I would try to find some means of vibrating the concrete. Otherwise I would worry that even with high slump, the concrete will bridge between the bars in places
RE: Use of concretes that can do without vibrators?Any warning?
RE: Use of concretes that can do without vibrators?Any warning?
RE: Use of concretes that can do without vibrators?Any warning?
The rebar sub then announced that self-consolidating concrete or not his contract was for placing the rebar one time and not for re-doing it after demo. Obviously he was making an early prediction on the self-consolidating part of the term "self-consolidating concrete".
So the stuff had a high cement content and had a high-range water reducer to make it very flowable. Slumps were 10 to 12" and not totally verifiable. Breaks at 3 days were 3000+ average. Upon removal of the edge forms in preparation for PT stressing we got our first clue as to the magnitude of the honeycombing yet to come. It took 4 guys 3 days to bush out and patch behind the anchors enough to get the PT stressing accomplished. The rest of the slab took 3 more days to get patched properly.
RE: Use of concretes that can do without vibrators?Any warning?
Your post seems to reflect an experience. But I havent properly understood, apart from the big lumps and high strengths.
Can you put it more clearer?
Nothing can replace fellow engineers experience.
respects
IJr
RE: Use of concretes that can do without vibrators?Any warning?
For road construction and other flat work, it appears that vibrating is not so critical.
For columns, walls and other tall structures, it may result in an unacceptable product.
Aggregate size probably should be reduced if the steel is "tight". This will allow better consolidation around the rebar. Note that this should be done whether the concrete is normal or high slump.
Rodding and tamping, external or pencil vibrators should all be used if possible. Don't let the Contractor tell you otherwise.
Make the Contractor responsible for quality - inspect after stripping, take core samples and be prepared for tear out and reconstruct. If the contractor is aware of your desire for high quality, he may decide to put a little more effort into it.
RE: Use of concretes that can do without vibrators?Any warning?
RE: Use of concretes that can do without vibrators?Any warning?
Richard A. Cornelius, P.E.
WWW.amlinereast.com
RE: Use of concretes that can do without vibrators?Any warning?
http://tinyurl.com/py2yv
RE: Use of concretes that can do without vibrators?Any warning?
RE: Use of concretes that can do without vibrators?Any warning?
But do not ignore real life situations, where teams involved in the project force you to use no more than the available space allocated to you(You sometimes do the same to them)
I find such situations to be what makes engineering worth practicing.
respects
IJR
RE: Use of concretes that can do without vibrators?Any warning?
Although this structure will probably never be loaded anywhere near failure, structures that are overly reinforced and loaded near failure do not behave like under reinforced sections designed in accordance with ACI. The bigest problem is that these failures may not be ductile but rather be a sudden failure.
The problem with project teams is that everyone else assumes that some has checked a part of the design. Also no one on the team wants to stand up a say we have a problem because everything is on a schedule. Sometimes the best thing to do is just stop and reevalute what you are doing. Most dramatic engineering failures were due to flaws that were rationalized away on several levels of review because a.) no one wanted to stop the schedule or b.) someone had assumed someone else must have reviewed the detail and it was ok.
If you can not place the concrete, this is an indication you are trying to force a solution to a problem. I think this may be a wake up call to reevaluate.
RE: Use of concretes that can do without vibrators?Any warning?
Thank you for sharing your experience. We truly are against modification of original designs, but there are so many cases we have to, trying to do so within technical limits.
Respects
IJR