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RE: Mat Foundation

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Thank you James,
This is exactly the information I was looking for.
It is heavy process equipment covered by a steel structure.

>>> James.Lutz(--nospam--at)earthtech.com 4/1/2005 12:27:25 PM >>>
If you are talking about joint filler, I wouldn't think so, assuming this is a grade slab. I don't know what the application for this mat is. The ones this size I have run into are usually foundations for heavy process equipment, and I assume you have reinforcement continuity across the pours. I would add some trim steel parallel to and on each side of the joints near the top for crack control, maybe heavier on the second pour side.
 
What happens is that the first pour is stronger and has already done some shrinkage by the time the adjacent pour is made. The second pour is weaker than the first one while it is in early shrinkage mode, and the restraint provided by the first pour tends to cause cracks in the second pour. Check the joints for shear capacity based on shear friction, and roughen them up before the second pour. I usually don't use keys.
 
If you must use dowels, consider using plate dowels instead of straight bars, which aggravate the shrinkage cracking problem. The plate dowels are square and installed with the diagonal aligned with the joint face, so that when the concrete shrinks the dowel doesn't restrain it in the horizontal plane.
-----Original Message-----
From: Abe Knapp [mailto:AKNAPP(--nospam--at)state.wy.us]
Sent: Friday, April 01, 2005 11:10 AM
To: seaint(--nospam--at)seaint.org
Subject: RE: Mat Foundation

Thank you James,
I imagine no cold joint material required in this situation?

>>> James.Lutz(--nospam--at)earthtech.com 4/1/2005 11:59:33 AM >>>
Pour sequence should start from near the middle and work out toward the edges.
-----Original Message-----
From: Abe Knapp [mailto:AKNAPP(--nospam--at)state.wy.us]
Sent: Friday, April 01, 2005 10:51 AM
To: seaint(--nospam--at)seaint.org
Subject: Mat Foundation

Fellow Engineers,
 
I am looking for some guidance on a Mat Footing.
It is 2 feet thick and 86'x75'.  Winterkorn and Fang recommend placing the concrete in approximately 30 foot square sections and letting each pour set for two days before placing the next adjacent area.  I am looking for some guideance on how to specify the joints.
Thanks in advance.
 
Abe Knapp
Wyoming


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