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Re: Concrete Boonding Agent (was: Caisson cold joint)

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If I remember correctly, these caissons are being used to resist lateral load. If the soil is loosened by water, there will not be a clean line where the loosened soil is removed and the remaining is as good as it originally was for bracing the caissons. I wouldn't allow water to be used in this situation.
 
Roger Davis

Padmanabhan Rajendran <rakamaka(--nospam--at)yahoo.com> wrote:
The second stage concrete would fill up any widened hole due to soil wash.

Raj

Roger Davis <sds_rdavis(--nospam--at)yahoo.com> wrote:
The caisson wouldn't collapse but the soil around the un-finished portion of the caisson could.
Roger Davis

Padmanabhan Rajendran <rakamaka(--nospam--at)yahoo.com> wrote:
If there is a risk of messing up with the use of bonding agent, don't use it.

If water is trapped, pump it out.  In uncased caisson, jetting would only remove loose concrete from the edges etc. It is difficult to foresee the collapse of the entire caisson.

rajendran

Roger Davis <sds_rdavis(--nospam--at)yahoo.com> wrote:
A bonding agent becomes a method of ensuring there is no bond if done incorrectly and it is easier to do incorrectly than correctly.  I would worry about using a water jet on a caisson. If it is cased, the water will be trapped and if it is not cased, it might cause the soils around the partially completed caisson to collapse.
 
Roger Davis
Architect
SDS Architects, Inc.

Paul Ransom <ad026(--nospam--at)hwcn.org> wrote:
> From: Padmanabhan Rajendran

> I don't have a problem with the suggested method of caisson construction.
> I would stipulate, however, that top of the first stage concrete is
> cleaned with water jet(to remove all loose material and to expose coarse
> aggregate) and a concrete bonding agent applied, before placing concrete
> for the last 4' of caisson.

I have encountered a concrete bonding agent specified on one project in
my career. Nobody on the site could explain to me why it was being used,
except that it was in the spec. Technically, I know what they do and I
know what characteristics they can develop across the interface. Perhaps
somebody can fill me in on the primary application and marketed purpose
of the product (the two may not be the same). Pros and cons? Anecdotes?

Regards
--
R. Paul Ransom, P. Eng.
Civil/Structural/Project/International
Burlington, Ontario, Canada


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Roger Davis
Architect
SDS Architects, Inc.

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Roger Davis
Architect
SDS Architects, Inc.

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Architect
SDS Architects, Inc.


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