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RE: 1 Inch Topping Slab

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I concur with Mr. Madden. 1 inch = too thin. It can be done at 1 inch,
Mr. Sprague has the right ideas, but it will be a bear to do right, and
you still have a huge potential for cracking as it shrinks, curling as
it dries abnd shrinks, and a potential service issue down the road when
it breaks up at the curled (delaminated) and cracked portions. Dowelling
to the existing may serve to help the bond but it will restrain
shrinkage so you may expect more cracks. An overlay material (latex
modified?) may be a better answer than a portland cement mix BUT....that
is big $$$ and low production rate work.

Even at 2 inches, there is a potential for problems but
 atleast you have a chance. Suggest that you require a LOT of joints, or
place it in strips and full depth sawcut, in addition to all of Harold's
sugestions. Less cement and more, larger aggregate = less

Richard W. Stone, P.E.
Project Executive
Technical Services/Project Management/Estimating
Concept Design/Engineering/Quality Assurance
Madison Concrete Construction Company
130 Quaker lane
Malvern, PA 19355-2479
email: rstone(--nospam--at)
Voice:       610.695.8800
Facsimile: 610.695.8678
Nextel:      610.496.5764
Visit our webpage at  !!!!
5                                Message:0005
From: "Gerard Madden, SE" <gmse4603(--nospam--at)>
To: seaint(--nospam--at)
Subject: Re: Slab-on-grade topping slab

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Too thin. Use 2" min topping otherwise spall city...


On Thu, Sep 11, 2008 at 1:29 PM, Brian <bsh117(--nospam--at)> wrote:

> I was hoping that I could get some input on my current situation.
> I have an existing warehouse slab that is 6" thick.  A potential buyer
> would like to have a 7" thick slab because that is what they require
> their typical specifications.  The loading does not dictate that a 7"
> is necessary.  The warehouse use would fall into the moderate or heavy
> warehouse slab as defined by ACI 302.1R.
> I planned on using a 1" thick, 5000 psi concrete topping slab (max
> aggregate) over the existing slab.  The topping slab would be bonded
to the
> existing with cement grout (or other proprietary bonding agent) and
> joints could be cut to match the existing.
> What do you guys think?
> I would appreciate any input.
> Thanks,
> Brian

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