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Re: Placing Concrete in Vault

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> Moni -
> 
> I'd specify a "pea gravel" mix (3/8" aggregate), plus the superplasticizer,
> but I wouldn't increase the slump past 4" or so.  Using the higher slump
> (6"-7") can potentially cause curing and cracking problems, especially since
> your walls are so thick.
> 
> Just my opinion.
> 
> Bruce Resnick, SE
> Parker Resnick Str. Eng.


Well but wouldn't the 4" slump lead to voids and seggregation in such a
heavily reinforced section, especially in the walls ?

I'm hoping that by using the superplasticizer to increase the slump to 6
to 7" without increasing the water cement ratio, the potential for
shrinkage and thus cracking is not increased.

Anyways, it seems that everybody agrees that the maximum aggregate size
should be 3/8" to 1/2" but the adequate slump and vibration method seem
debatable.
Maybe a trial on a mock up section could be usefull !

I guess concreting is somehow like cooking: sometimes all the
ingredients are carrefully weighed on the balance and the dish comes out
tasteless and sometimes the  dish with the same ingredients and
proportions comes out really good !


Thanks to yo'all's input,

Moni Serhal