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RE: Concrete on reinforcing

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I would think that if the concrete coating on the rebar is clean, sound,
and well adhered, it should not be a big problem.  The fresh concrete
placed around it likely would bond well to it, as the in-place concrete
will absorb water from the wet concrete and bond the interface.  Thus,
the biggest concern should be that any loose or unbonded concrete be
removed and the surfaces are clean. 

William C. Sherman, PE 
(Bill Sherman) 
CDM, Denver, CO
Phone: 303-298-1311
Fax: 303-293-8236
email: shermanwc(--nospam--at)cdm.com
 

> -----Original Message-----
> From: Jared Keyser [mailto:jkeyser(--nospam--at)LCMF.com] 
> Sent: Thursday, June 16, 2005 12:09 PM
> To: seaint(--nospam--at)seaint.org
> Subject: Concrete on reinforcing
> 
> Dear list,
> 
> I am looking for a reference that addresses cleaning off of 
> concrete buildup (i.e. from a previous pour) on exposed 
> reinforcement prior to subsequent pours.  ACI 301 5.7.2 and 
> its sister language in the IBC are the only references I have 
> been able to find. They state "All reinforcement, at the time 
> concrete is placed, shall be free of mud, oil
> or other materials that may adversely affect or reduce the bond."   
> 
> We have a job under construction where the contractor was not 
> very careful in placing or subsequent cleaning of the exposed 
> reinforcement or the cold joint (which is another issue).  As 
> such, the majority of the primary longitudinal reinforcement 
> in the concrete grade beams is currently gray with concrete 
> of varying thickness based on photos received from the 
> special inspector.  I believe that this concrete coating (for 
> lack of better term) must be removed prior to placement of 
> the next pour.  My thoughts are that sand blasting is 
> probably the only means at this point that will sufficiently 
> clean both the cold joint surface and the concrete caked on 
> the exposed reinforcement.
> 
> I would be interested in opinions from the list.
> 
> Thanks in Advance,
> 
> Jared F. Keyser, P.E.

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