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RE: Concrete Slab Cracking

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Is there a pattern to the cracking?
Is it in an isolated areas?
Was your reinforcement placed correctly?
How long after the concrete was placed did the cracks appear?
Was the concrete cured properly?

Ralph Benson
Huitt-Zollars, Inc.

 -----Original Message-----
From: Francis.Ang [SMTP:Francis.Ang(--nospam--at)toyota.com.ph]
Sent: Tuesday, July 06, 1999 8:16 AM
To: rbenson; seaint
Subject: Concrete Slab Cracking


Yesterday, I visited the site of a new Toyota Dealership in Manila Bay
(Toyota Manila Bay) which is a reclaimed area in the Philippines. I
noticed
that the slabs (which are anchored to the tiebeams and pile caps) are
suffering from cracks. This happened after the painting of the floors
have
been finished. I think they used epoxy paint finish for these floors. I
verified with the project manager about the cracks and they said they
could
not figure out the source.

According to the Project Manager, they have attained a more than 95%
compaction (Modified Proctor Test). That's one of the specs of the
structural engineer of the project. They are wondering if the cracks are
due
to temperature change or due to painting works. I had to comment that if
they were temperature cracking, their widths would just be limited. I saw
cracks ranging from 2-3mm wide.  And also, the floors are covered by the
roof with heat insulation so temperature changes would be a minimal
factor.

The problem is that the project is being rushed for an earlier opening.
It's
already delayed for about 2 months. The floors would be loaded by several
equipments like vehicle lifters and auto stuff. Moreso, vehicles like
Land
Cruiser and Delivery Trucks would use these floors. It might suffer some
cracks in the future which would become an eyesore.

I just would like to know some remedies or solution for these problems.
Any
suggestion would be highly appreciated. Knowing that the soil is
expansive
in nature (the place is a reclaimed area, highly prone to liquefaction in
case of earthquakes), I suggested that we move in some large vehicles in
the
area. This would make the soil underneath the slab react and future
crackings can be observed and rectified.

I need some verification or comments on my suggestion. They would be
doing
this in a matter of days. I do think that my suggestion is one that can
be
subjected to a lot of comments and rebuttal, but it's the most we can do
since the project is in a rush.

Thanks in advance !

Allan Yango
CE/SE
Toyota Motor Philippines