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RE: Concrete slump

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Hi James,

I may be able to help you.  If any of my answers is incorrect, please
correct me so that I will have the correct information

James wrote:
<<Does anyone have experience or know of technical resources that address
the change of concrete slump during placement by pumping.>>

<<I have been told that the pumping process changes the concrete slump.>>

<<1. Is this correct?>>

Yes this is correct.

<<2. If pumping does change the slump does the slump increase or decrease?>>

My understanding from experience and speaking with concrete suppliers, the
slump decreases.


<<4. If the slump changes where does the additional water come from if the
slump increases or where does the water go to if the slump decreases?>>

The slump decreases because of the pressure of the pump.

<<5. If the pumping process changes the slump, what is the slump? Is it the
slump of the design mix prior to pumping or after?>>

I believe the pump reduces the slump by at least 1/2"~1".

My understanding is that the slump is suppose to be taken from the truck.
That is what the code asks.  This is more conservative way to take the
slump, if you measure a slump of about 4" out of the truck and it comes out
of the pump at 3 1/2", the concrete will be theoretically stronger.

Anyone that can correct me, please do, I got those answers by basically
asking concrete suppliers while I am out at the job site.