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RE: construction joint spacing for SOG

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One of the best industrial flooring specialty firms is Kalman Flooring
Company in Evergreen, CO  They
use shrinkage compensating concrete and many other details and features that
mitigate cracking.  I have designed my own floors and I have used Kalman.
If I can put control joints in at 15' to 30', I will design my own
(including: monitoring QC, and special inspection).  If the control joint
spacing is 100', I will use Kalman or post tension the slab on grade.  

I never use thickened edges, because they act like anchors as the concrete
shrinks.  I prefer using greased square dowels with PNA (800-542-0214)
Expando-Lok Clips.  Joints in heavy traffic areas should be armored with PNA
steel bar armored joints.

Any saw cut joints should be cut with an early-entry dry-cut system such as
the Soff-Cut (909-272-2330) saw.  Regular saw cut joints will be put in too
late to do any good.  

Keep in mind that from edge to edge a concrete slab will try to shrink to
the center.  Provide a positive slip plane, and eliminate restraints like
turned down edges, dock leveler pits, and column base turn downs.

I would recommend that you read "Shrinkage & Curling of Slabs on Grade",
Robert Ytterberg, April, May, June 1987, Concrete International.  It is
available from Kalman Floor Company.  You might also check out the Concrete
Floor Contractors Association of Ontario

Steel fibers can be effective, but they are very dependent on the
contractor's (concrete supplier, finisher, etc.) ability.  They are not a
cure all.

Speaking of cure, do the wet cure.

Harold O. Sprague

> -----Original Message-----
> From:	David Handy [SMTP:dhandy(--nospam--at)]
> Sent:	Thursday, January 04, 2001 10:20 AM
> To:	seaint(--nospam--at)
> Subject:	construction joint spacing for SOG
> We are designing a slab on grade for an industrial occupancy with moderate
> fork truck loading. We have used the PCA-type approach as outlined in
> Ringo 
> and Anderson's book. We have used the Subgrade drag equation for the basis
> of calculating steel area in slab.
> 	F L w
> As = --------------
> 	2   fs
> The value of L is the slab length between free ends which we have assumed 
> is the distance between construction joints. We have detailed a formed key
> at the construction joint with no steel running through. The slab is 
> thickened at these locations to account for the effects of loading at a 
> non-continuous edge. In our case we were using 10M (little bigger than #3)
> at spacings to suit the value of "L".
> 1.  We design thickness for loading on the interior of the floor slab.
> What 
> about the control joint locations. Would not a sawcut of 1/4 depth be 
> treated as a dowelled joint therefore causing the slab to require 
> thickening at all control joints? Because of this you would end up
> treating 
> the entire slab as being partially unsupported because the suggested 
> tapering for thickness changes is 1:10.
> 2.  At free ends we used slab thickening with a formed key with no steel 
> running through. Any comments? The frequency of the construction joints is
> almost dictated by a reasonable amount of reinforcing. This seems to be 
> construction joints that are a little too close (70' to 100'). Any
> thoughts?
> 3.  I just received a call from a manufacturer of steel fibres. They sound
> great but I have not used them before. The most important thing in this
> job 
> is too have NO cracking as this is replacing a cracked floor that was 
> constructed not too long ago. Has anybody had any negative experiences 
> using the steel fibres? They are suggesting the total replacement of the 
> steel with the steel fibres.
> David Handy, P.Eng.
> dhandy(--nospam--at)