Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

RE: slab on grade

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Could this have been partly due to a poor concrete mix (i.e., too high w/c )
or poor curing ?

	-----Original Message-----
	From:	Harold Sprague [SMTP:harold.sprague(--nospam--at)]
	Sent:	Tuesday, January 05, 1999 9:38 AM
	To:	'seaint(--nospam--at)'
	Subject:	RE: slab on grade

	I just inspected a project with the worst drying shrinkage cracks
that I have ever seen.  The cracks were 5/8" wide and there were many of
them.  It was a slab using polypropylene fibers.  I would not count on
fibers except for control of bleed water and plastic shrinkage cracks.
	You have already seen posts on post tensioning which is a good
	Consider also shrinkage compensating concrete.  
	Another thing is to eliminate as many restraints as possible.  Avoid
thickened areas.  Any penetrations by pipes, light standards, etc. should be
wrapped with a closed cell foam and sealed.  This allows the slab to shrink
without being restrained by the penetrating structures.  Add reinforcing
steel around any penetrations.  Try to create a good uniform slip plane and
eliminate restraints.
	Harold Sprague
	The Neenan Company
	harold.sprague(--nospam--at) <mailto:harold.sprague(--nospam--at)> 

	-----Original Message-----
	From:	jdcoombs(--nospam--at) <mailto:jdcoombs(--nospam--at)>
[mailto:jdcoombs(--nospam--at)] <mailto:[mailto:jdcoombs(--nospam--at)]> 
	Sent:	Monday, January 04, 1999 11:35 AM
	To:	'seaint(--nospam--at)'
	Subject:	slab on grade

	Happy New Year, y'all
	I need to put in a good slab for outdoor basketball courts.  The
client would like for them to be free of joints.  It will be an unloaded
slab, no traffic.  The slabs will be 100' x 65'.  I can spec a proper
subgrade spec.  How do I design for the slab thickness and reinforcing
required to keep cracking controlled.  I have reviewed  ACI 302 and 360, and
the PCA guide.  None really address the unloaded slab except fot the
"subgrade drag equation", which is not really a qualitative approach.  I'm
willing to add fibers to get a good crack control, but how does one balance
between that and steel?  How thick a slab?  How much steel?  How much
fibers?  Any comments are appreciated.
	Jerry D. Coombs, PE