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Column concrete placement

Column concrete placement

Column concrete placement

(OP)
Is it ok to place column concrete by pumping it into the top of the column form? Is there any concern about segregation? The column clear height is about 9 feet.

RE: Column concrete placement

You should be fine so long as the stream of concrete doesn't have to bounce off of, and be separated by, rebar. Here's some info on exactly this problem: Link. This comes up often in pile construction and always ends up being permitted in my experience. This too: Link.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Column concrete placement

Along the lines of the items KootK provided, it also depends on your mix. Higher slump mixes and especially self-consolidating concrete I would be a lot less worried about this than a real low slump mix. We typically don't specifically limit free fall, as it's rather impractical to not just fill forms up from the top. Would say a majority of the honeycombing and other defects I see are typically mechanical consolidation issues, not caused by free fall or segregation caused by running into rebar or other embedded materials. Once the mechanical consolidation issues are addressed through either better construction practices or mix modifications that better cover up the subpar mechanical consolidation, the issue typically goes away without making any changes to where the concrete is deposited.

The main concern I've seen with regards to segregation isn't necessarily with free fall, but with horizontal transportation as the last sentence in JAE's second screenshot states. The intent of ACI 301 in my eye isn't for you to pour columns and walls in lifts or stick your conveying equipment down into the forms. It's more to not deposit all concrete for a long length of wall or slab in one spot tens of feet away and then move it into place from there.

RE: Column concrete placement

I agree with MrHershey. Lack of compactive effort and leaky forms are the major problems in placing concrete in columns.

RE: Column concrete placement

(OP)
I was meaning to direct my question to whether pump mix, pump discharged to the top of the column, was ok. Is it any worse than a bucket discharged mix to the top of the column (without elephant trunk).

RE: Column concrete placement

No different, IMHO.

RE: Column concrete placement

(OP)
Thanks Hokie66. What is IMHO?

RE: Column concrete placement

I thought it was "in my humble opinion".

BA

RE: Column concrete placement

(OP)
When using self consolidating concrete on another project a few years ago, we specified that it be pumped pumped in from the bottom, thru a gate valve. It worked well. My recollection was that it is not advisable to pump self consolidating concrete by discharging into the top of the formwork.

RE: Column concrete placement

For a 9'-high formed column, I wouldn't dump the mix into the top of the form (whether by pumping, or bucket dropping) and simply hope that it doesn't segregate. Get a pipe, or elephant trunk, and place it from the bottom up.
Dave

Thaidavid

RE: Column concrete placement

Yes, BA, humble seems more correct in text slang dictionaries. I had seen some explain it to be honest in non-technical forums.

RE: Column concrete placement

I checked it on the acronym site. They are both listed, but I thought the best one is:

IMHO: Is My Hearing Aid on?

BA

RE: Column concrete placement

(OP)
LOL.

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