Specification for pumping/pouring concrete 2

[1309]

I am trying to find the Building Code/ACI reference specifying the maximum height of free fall of concrete for placement in reinforced steel structures. Can anybody help me with the code reference?

 

[SirAl]

Try this link

http://www.cement.ca/cement.nsf/internetE/212277F323D63B83852568B3004B3CFF?opendocument

It provides a brief discussion followed by some good references.

 

[Focht3]

You should also look for a paper written / co-authored by Clyde Baker (STS Consultants) in Chicago. The paper dealt with the claims of aggregate segregation in caissons (drilled piers) where the fluid concrete was allowed to strike the rebar cage. The paper's authors concluded that construction requirements that prohibited allowing the fluid concrete to hit the rebar cage were largely unfounded.

Sorry I don't have the citation handy -



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[dirtsqueezer]

There is no official code reference that I know for free fall of concrete. Classes taught by the DCLU Seattle instruct that free fall from any height is allowed for plain concrete without steel. Concrete with reinforcing steel will tolerate on the order of 4 feet before the hackles start to rise. The danger with free fall through steel over large heights is that it will segregate the falling concrete like 3-D wire mesh, and you'll end up with rock pockets in your final structure, compromising its integrity, not to mention its looks. The conventional solution is just to rent a concrete pump and have the operator place with a long whip (rubber hose at the end of the boom). If you have to place with a crane, you can use a tremie, which is basically the same, like a big funnel with a long rubber hose that goes on the end of your basket. Either one of these will convey your concrete past the reinforcing steel, and safely into place. There is also just blow and go, but that doesn't make one feel warm and fuzzy on those nice Sundays when you want to relax. Hope this helps.

 

[Qshake]

Focht3,

I've heard about that but never have seen the practice since many organizations will allow only a maximum of 5'. After that a section of pipe or trunks with hoppers are necessary.

Many of the books on construction inspection have the 5' drop height referenced but no back-up or explanation. The same is true for most state DOT's that I've worked with in the past.

 

[Focht3]

Like so many things we do - "cuz". I haven't found the source of the 5 foot limit on free fall, either. If someone is in the Chicago area, contact STS and get in touch with Clyde Baker - he's a nice guy. See what light he can shed on the subject -



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