×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Checker board slab on grade
8

Checker board slab on grade

Checker board slab on grade

(OP)
Does anyone know the specifications for checker board slab on grade placement. it's a 6 inche slab thick over an area of 300 ft x 700 ft. How do I show this on a drawing? What are the min or max area patterns and where can I find this information.

Thank you always

Rain

RE: Checker board slab on grade

I typically show control joints on the Foundation Plan.  For a 6" slab, spacing of joints should not exceed 18'.  In your specifications, or Structural General Notes, mention that you want the slab poured in a checkerboard fashion.

DaveAtkins

RE: Checker board slab on grade

2
Don't bother with a checkerboard placement scheme.  There's no advantage.  The shrinkage compensation is so small for the time delay in placement it isn't worth.  Make sure your joints are properly spaced and cut at the right times and you'll do far more to mitigate cracking than the checkerboard pattern.

Joints should be spaced no greater than about 30 times the thickness of the slab, so if you have a 6" thick slab, your joints should not exceed 180" or 15 feet, in either direction.  The joints should be saw-cut the same day as placement, as soon as the saw can cut into the concrete without ravelling the coarse aggregate, and should be cut to a depth of 20 to 25 percent of the thickness or 1.2 to 1.5 inches deep in this case.

RE: Checker board slab on grade

Ron said it well.  However, there may be visual reasons for this kind of placement, rather than using sawn joints. If so, carefully attend to Ron's recommendations.  I hope your results are acceptable.

RE: Checker board slab on grade

For 300' x 700', I would also be thinking really carefully about location of expansion joints in the slab, especially if it is exposed to strong sunlight and/or subject to seasonal temperature changes.

RE: Checker board slab on grade

I like to echo Ron's sentiments regarding checkered slab placement. They do not work that well at all. I have much better luck with well placed construction and contraction joints. The rule of thumb that I use is 2.5 times the slab thickness in feet. I read this rule some where and it served me well.

There are lots of rules, what to do and what not to do for SOG joints. Also watch for catch basins, they can present a tricky area for joint.

Regards,




Lutfi
www.cdeco.com

RE: Checker board slab on grade

Mudadi - In your previous post on this subject you did not give the slab thickness. It is always amazing how each of us has our own (arbitrary) mental picture of the problem. When I said that a checker board pattern was a good way to go I had made an (incorrect) assumption that your 300' x 700' slab was probably 8 or 10 FEET thick (not uncommon for an industrial slab that size).

For a 6" thick slab, I totally agree with the advice from Ron, and others. Here are some links with other backup information:

Long Strip Construction Preferred http://www.concreteconstruction.net/pclinic/pc_template.asp?ProbClinicID=C910755A

Pour Size For Floors
http://www.concreteconstruction.net/pclinic/pc_template.asp?ProbClinicID=C99A089a
and
http://www.concreteconstruction.net/pclinic/pc_template.asp?ProbClinicID=C03K059A


www.SlideRuleEra.net

RE: Checker board slab on grade

Two additional suggestions:

1.  Specify a "SoftCut" saw for cutting the joints.  It allows the contractor to cut the joints much sooner than the conventional paving saw.

2.  For design recommendations see the book by Boyd Ringo with a title something like "Design of Industrial Floor Slabs" (Sorry, I'm not near my bookshelf!)

RE: Checker board slab on grade

(OP)
THANK YOU EVERY ONE FOR YOUR INFO. IT WAS VERY, VERY HELPFUL. KEEP UP THE SPIRIT, RON SLIDERULEERA, EMMGJLD, SACREBLUE, LUFTI, JHEIDT2543

THANK YOU THANK YOU THANK YOU!

RE: Checker board slab on grade

Here is the correct citation:

"Designing Floor Slabs on Grade, Step-by-Step Proceedures, Sample Solutions and Commentary", 2nd Edition, by Boyd C. Ringo and Rober B. Anderson, published by The Aberdeen Group, 426 South Westgate, Addison, IL 60101, ISBN 0-924659-75-0

One of the best!

RE: Checker board slab on grade

jheidt2543,
Isn't the proprietary name you mentioned above spelled "Soffcut"?  I think it is a concrete saw with a very wide wheel (so it doen't sink into the concrete) and a handle which the operator holds.

DaveAtkins

RE: Checker board slab on grade

DaveAtkins:

Yes, you are closer, but actually it is Soff-Cut by Soff-Cut International and here is their website link:

http://www.soffcut.com/

Thanks for making me look it up, it is an interesting website!

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources