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RE: Bar Placement in Slab with Laser Screed

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Kalman Flooring is one of the best I have ever watched.

They put all of the rebar on grade and drive the laser screed on top of the rebar mat as required to get position. They place in 100 ft x 10 ft strips with the screed The place the rebar on chairs in just the outer 10' strip. They then place the concrete and laser screed the concrete. After they reach the end of the 100' x 10' strip, they set the rebar in the next 10' strip and place the concrete and laser screed in that next 10' strip. They will place all of a 100' x 100' area in 10' strips. The 100' x 100' area is the boundary where they put expansion joints.

They can place a lot of concrete in a hurry with the only lumps in the slab being attributed to slow inspectors.

Regards,
Harold Sprague




From: "Rich Lewis" <sea(--nospam--at)lewisengineering.com>
Reply-To: <seaint(--nospam--at)seaint.org>
To: <seaint(--nospam--at)seaint.org>
Subject: Bar Placement in Slab with Laser Screed
Date: Thu, 31 Mar 2005 09:56:23 -0600

I was watching the tail end of the pour of a slab on ground this morning and
was discouraged with the placement of steel.  What was supposed to be top
bars in the slab for shrinkage control ended up as middle or bottom bars.
The bars were up on chairs, but the placement method pushed them down.



The slab was screeded with a laser screed. It's called a 240 screed because
it is 12 ft. wide and has a 20 ft. reach, making 240 sf per pass.  The
screed pulls the concrete towards itself.  The tires on the screed push the
rebar and any chairs down into the ground.  So when the concrete is pulled
up to the screed it is holding down the rebar.  Now when they move the
screed they attempt to pull the bars up, but in a 6-8" thick slab you can't
pull bars up from the bottom to the top.  It is impossible.



Isn't there some method to use the laser screed and still get top bars?  I
asked the operator and he said this is how it is done all the time.  I'm
wondering why hasn't this been perfected yet? If it was truly critical that
I get top bars for a strength reason there is no way I could count on it.



Has anybody developed a placement specification and method to cover this
situation?



Rich Lewis

Lewis Engineering






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