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Re: Slab on grade

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Is the red clay expansive.  Have you considered post-tensioning the slab?
-----Original Message-----
From: Horning, Dick/CVO <dhorning(--nospam--at)>
To: 'seaint(--nospam--at)' <seaint(--nospam--at)>
Date: Thursday, October 08, 1998 8:58 AM
Subject: RE: Slab on grade

>Gee, and I thought my wife's 3-stall horse barn was the ultimate "Honeydo"!
>Seriously, jointing @ 27' is a good idea, but should be done in both
>directions (i.e., 27'-0" x 26'-3" panels)  I would also add well-greased
>smooth dowels at the joints to transfer wheel loads across.  Fiber
>reinforcing with polypropylene fibers would greatly add to the flexural
>strength of the slab.  I've heard of as much as 15#/C.Y. being used in
>tunneling, but we only call for 1.5# in topping slabs.  Optimum seems to be
>2% by volume (about 30#/yd ?)  Synthetic Industries, Fibermesh Division, in
>Chattanooga, or Forta Fibre in Grove City, PA, should be able to advise
>Steel fibers would probably stick out of the surface and be undesirable.
>Good Luck!  Now you get to see what you really know about engineering.
>DISCLAIMER:  The preceding is my personal, humble opinion, and does not
>represent my employer in any way.
> -----Original Message-----
> From: Phil Hodge [SMTP:phil(--nospam--at)]
> Sent: Thursday, October 08, 1998 8:43 AM
> Subject: Slab on grade
> I am writing this not as an engineer, but as an owner/contractor.
> experience, both as SE and contractor, is exclusively with steel.
>All I
> know about concrete is that it cracks.
> I am acting as
> anyone-can-think-of on a 54'x105' hangar.  (I've always heard that
> anyone who acts as their own attorney is employing a fool, does the
> apply to engineers?  It's fun wearing all the hats!)
> I plan the SOG to be 6" 3000 psi concrete with #4@12" both ways in
> middle, and a 12"x12" thickened edge, tapered to normal slab
> at 2:1, on 4" clean gravel.  The footings are not cast integrally
> the slab.  Soil is well compacted red clay common to eastern
> Use will be for planes less than 3200#, plus dump trucks, backhoes,
> any other toys my wife acquires.  The finisher is just that, a
> finisher.  He knows nothing about the stuff we're supposed to worry
> about - rebar placement, crack spacing, mix, etc.  Three questions:
> 1)  How often should I cut control joints.  I will form and pour the
> slab in two pours on seperate days, each 27'x105'.  I want the
> number of joints, but I also don't want any random cracks.
> 2) What about fibers?
> 3)  Is there anything in the above that jumps out at those
> with concrete and shouts "This guy is an idiot"?  Anything I should
> different?  Again, suggestions?
> By the way, if there are any pilots out there comfortable on 1900'
> grass, The 100 Aker Wood private field is at N85d46' W84o46'.  Drop
> someday.
> Phil Hodge
> phil(--nospam--at)