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RE: Slab Stripped before time ...

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There is a trough in the slab (no evidence of thickening that would occur if
during pour) that suggests that the deformation occurred after the pour ...

-----Original Message-----
From: Alex Nacionales [mailto:alex1961(--nospam--at)telus.net] 
Sent: Sunday, May 08, 2011 4:35 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: Slab Stripped before time ...

Thor,

 It may be that the deformation occurred during pouring due to inadequate
formwork and/or shoring in which case the slab has thickened in the areas
where the form joists deflected or where shoring subsided to the ground due
to inadequate shoes. If deformation occurred after concrete set then it
would have failed completely if not after stripping, after being loaded.

MTCW

Alex Nacionales





-----Original Message-----
From: Thor Tandy [mailto:vicpeng(--nospam--at)telus.net] 
Sent: Sunday, May 08, 2011 2:41 PM
To: SEAInt
Subject: Slab Stripped before time ...

Interesting question .

 

I have been asked to do a structural review of an existing residence that
has a significant area of the footprint a suspended slab on circular
columns.

 

I understand that the slab formwork was stripped before the slab had
completely cured . yes there is a noticeable trough in the main part of the
slab.

 

It is a 6"+/- slab and the two-span is approximately 15ft and the main
deformation is probably about 2".  Built in 1990 the original owner, who is
now selling, accepted the flaw.  There has been no
perceived/recorded/admitted problem since.

 

In general the construction looks good and, except for some spalling of
columns due to bits of tie-wire at the surfaces, appears sound.  The
formwork was sonata and although I have to get the original construction
dwgs but I assume the reinforcing was tied steel cages.

 

My questions:  

 

1)      Does anyone know of literature on, or record of, impact on the
strength and/or serviceability of slabs that have deformed during the
curing/strength-gain period?

2)      Although the spalling appears localized to the tie-wire locations,
there is number of them.  Could this also be a sign of deeper issues?  I.e.
would the tie-wire spalling open up access to the stirrups etc in the
column?

3)      Has anyone scanned columns for internal content checks?

 

Thanks

 

Thor A. Tandy P.Eng, C.Eng, Struct.Eng, MIStructE
Victoria, BC
Canada 

 

 




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