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Re: Free-Fall of Concrete

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What makes high lift cmu grouting acceptable and greater than 5ft drop
of concrete not?

On Tue, Apr 29, 2008 at 12:35 PM, Garner, Robert
<rgarner(--nospam--at)moffattnichol.com> wrote:
>
>
>  http://mail.google.com/mail/#inbox/1199a881a6f2cf83
Gmail - Free-Fall of Concrete - gtg740p(--nospam--at)gmail.com
>
> This was back in the '70's so my memory is taxed, but as I remember, we had
> a system of conveyor belts to reach the caissons, which were driven in the
> Hudson River, just offshore.  The concrete was free-fall from the end of the
> conveyor.  We had engineers working for us (I was just a draughtsman at the
> time) and this shouldn't have happened.  And we paid for it.
>
> Some day let me tell you about dredging too deep too close to shore on that
> job, and creating a mud-wave which displaced most of the caissons.  What a
> great way to learn!
>
> ps: This is that sewage treatment plant in NYC with the State Park over it.
>
> pps:  Even the mechanical had some learning processes - I don't believe the
> odor problem has been solved to this day.
>
> Bob Garner, S.E.
>
>
>
>  ________________________________
>
>
> From: William.Sherman(--nospam--at)CH2M.com [mailto:William.Sherman(--nospam--at)CH2M.com]
>  Sent: Tuesday, April 29, 2008 8:54 AM
>
>  To: seaint(--nospam--at)seaint.org
>  Subject: RE: Free-Fall of Concrete
>
>
>
>
> Do you know how much care was taken in the upper part of the free fall?
> I've seen articles that say that free fall works as long as the concrete
> does not impact any obstructions (rebar, sides of the hole, etc).
>
>
>
> If the concrete was not controlled to drop vertically in the center of the
> hole, segregation due to impact with the rebar or sides of the hole could
> have occurred.
>
>
>
> Drop chutes are still the safest approach.
>
>
>
>
> Bill Sherman
>
> CH2M HILL / DEN
>
> 720-286-2792
>
>
>
>
>
>
>  ________________________________
>
>
> From: Garner, Robert [mailto:rgarner(--nospam--at)moffattnichol.com]
>  Sent: Tuesday, April 29, 2008 8:21 AM
>  To: seaint(--nospam--at)seaint.org
>  Subject: RE: Free-Fall of Concrete
>
> I worked for the contractor in building New York City's West Side Treatment
> Plant.  We had 36" diameter steel pipe caissons that were driven to rock and
> then socketed into the rock.  There was rebar only in the top of the
> caissons.  We filled the caissons with concrete, using free-fall.  Everybody
> thought it was working until the Resident Engineer had us make an
> exploratory boring through the concrete in several of the caissons -
> DISASTER!!  Voids were found.  More borings had to be made.  More voids were
> found.  This one cost us large!
>
> Bob Garner, S.E.
>
>
>
>  ________________________________
>
>
> From: Jerry Coombs [mailto:JCoombs(--nospam--at)carollo.com]
>  Sent: Tuesday, April 29, 2008 7:10 AM
>  To: SEA ListServe
>  Subject: Free-Fall of Concrete
>
>
>
>
> Howdy, Y'all.
>
>
> I've seen many specs and General Notes that don't allow free-fall of
> concrete more than 5 ft (tremie or other means req'd).  There is nothing in
> any code documents that I'm aware of that nix free-fall.  Frankly, I don't
> see anything wrong w/ it and agree with the one article I've seen addressing
> it.  Maybe a very long drop and large aggregate may cause some of the
> aggregate to bounce off the concrete below separating it.
>
>
> I'd like to to hear what others are doing and any documented results or
> articles supporting either.



-- 
Will H.

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