What is the perfect slump for the concrete which will be used for a stationary pump for a pipe line has a height more than 90m ? i am thinking it should be at least 250 mm.

Not to wet! 250 might be to high.. I'm quite sure actualy but correct me if I'm wrong anyone. If your wearing parts are only just a bit worn out you might get seperation there.. I'd say a 220 max . Try to get them to reduce the amount of rock. Use rather some retarder to make sure it keeps the wanted slump for a longer time...

I'd be more stressed if I had a very high slump than a bit lower one.

A focus on slump alone is too simple:

1) slump could be changed by admixtures more than the pumpability is changed by them

2) <2" (50mm) slump could be pumped up 90m if everything else is good

Better questions:

Using largest diameter pipe (not hose) that makes sense?

Volume output expectations not excessive?

Robust enough (available power and pressure) equipment that is well maintained?

Mix design contains enough mortar content, wet enough water/cement ratio, pre-soaked agg if lightweight, and proper agg/sand gradation used?

Shady.. Just out of pure interest... How long have you been driving concretepump?

i tried before slump from 220 to 250 mm in a stationary pump we were pouring a wall for silos using slip form the height of the silo around 80m it was runinng 24 hour at least for 2 weeks without stop .so in this time we were using a two type of super plasticaiser .we never had any problem in pipe line or in cleaning we didnot have to use comppresed air or water in this time.

i think this photo is mine i posted it before .this is always happen when slump is too high the mortar is going and the aggrigate will stay in the packet.

i am not working on a concrete pump,i am working in maintenance but some time i had to set the pipe lines .

The picture of the hopper full of rocks is some of the nastiest crap I have ever seen.

Yes its your picture.. I was looking around in you topics to figure out what ''kind'' of operator you are.. ;-)

Slump 250 just sounds very high to me. Unnessesary high... Much more risk to get a hopper full of that sh't on the picture. 

79xlch, here's another one for you. Gotta love huge dry agg, they pump so well.

so is better for imroving the pumpabilty of concrete to increase the fine aggreigate than the coarse aggregate?

Someone needs a TB-130 bad.

YES 

shady: large agg will never improve pumpability, only increase the potential for plugs. On the other hand, too much sand (or manufactured sand) can be a negative and cause plugs too. A good gradation that fills in the gaps in each size is best if you can get it.

If interested, ACI has two publications that discuss gradation: ACI 302 for sand and ACI 304.2 for agg gradation for pumping. http://www.concrete.org

Other rules of thumb:

Water/cementitious (W/C) ratio greater than .30 (.40 to .60 preferred)

Mortar volume >45%

Powders >400 lbs/cu yd (if >700 lbs/yd watch for low W/C) 

The perfect slump to me is what concractor is paying for. Mix design from supplier approved by architects.

My answer everyday is......as long as it comes out that big black hose at the end of the boom....I am good.

Its a bit different here. If I see the crew struggeling I do everything I can to make their life easyer. Mostly that only means 1 phonecall to the factory to ask for the slump that is perfect for the job. Or we mix some liters of plasticizer in the load.. Or fiber if we need it stiffer.. Only happy customers..

here is what i had to deal with one day lol