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Re: Rusted rebars

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The answer was hidden in the commentary to ACI 318 where in section R7.4 it
states "Research has shown that a normal amount of rust increases the bond.
 Normal rough handling generally removes rust that is loose enough to
injure the bond between concrete and reinforcement"

A supprising number of questions will be answered if we just read the
commentary.


Mark Gilligan

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Message text written by INTERNET:seaint(--nospam--at)seaint.org
>On Mon, 24 Apr 2000, Julian Chu wrote:

> Is there any reference/standard regarding rusted rebars to be poured with
new slab? We have an existing structure with some exposed rebars left
unprotected for several years. Those bars were designed to be lapped for
later phase of construction. Can someone use wire brush to brush off the
rust and reuse them for the lapping?    
> 
Simply brushing the rebars will not solve any problem. If corrosion has
started, it requires chemical treatment. Several commercial products are
available in the market. If the loss of cross-section is significant, this
factor should also be considered and the loss overcome.

Ductile detailing requires that all rebars can not be lapped at the same
section. When the additional portion of the structure is constructed,
welding, plate bolting or other similar procedure may be required for
transfer of stress from the additional rebars to the old ones in order to
ensure the required ductility.

Hope this provides some additional information.

ravi sinha
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