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RE: Slab on grade

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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 you.
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)joistdesign.com]
	Sent:	Thursday, October 08, 1998 8:43 AM
	To:	SEAOC
	Subject:	Slab on grade

	I am writing this not as an engineer, but as an owner/contractor.
My
	experience, both as SE and contractor, is exclusively with steel.
All I
	know about concrete is that it cracks.

	I am acting as
engineer/contractor/owner/banker/inspector/anything-else-
	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
same
	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
the
	middle, and a 12"x12" thickened edge, tapered to normal slab
thickness
	at 2:1, on 4" clean gravel.  The footings are not cast integrally
with
	the slab.  Soil is well compacted red clay common to eastern
Tennessee. 
	Use will be for planes less than 3200#, plus dump trucks, backhoes,
and
	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
minimum
	number of joints, but I also don't want any random cracks.
Suggestions?

	2) What about fibers?

	3)  Is there anything in the above that jumps out at those
experienced
	with concrete and shouts "This guy is an idiot"?  Anything I should
do
	different?  Again, suggestions?

	By the way, if there are any pilots out there comfortable on 1900'
of
	grass, The 100 Aker Wood private field is at N85d46' W84o46'.  Drop
in
	someday.

	TIA

	Phil Hodge
	phil(--nospam--at)joistdesign.com