×
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

Slab on Grade Bottom Bar Location

Slab on Grade Bottom Bar Location

Slab on Grade Bottom Bar Location

(OP)
How much concrete cover is generally used for bottom slab bars in slab on grade?

ACI generally requires 3" for concrete cast against soil, but how about in the case when the slab is cast on a significant vapor barrier?

RE: Slab on Grade Bottom Bar Location

whats the depth of grade, and whats the slab being used for?
Usually we use 50mm cover but with a high strength concrete.

 

RE: Slab on Grade Bottom Bar Location

If the vapor barrier is thought to stand well for the environmental attack for the life of the building, a cover as interior placement or as provided by the code for such case can be used; this is the case for our CTE (Código Técnico de la Edificación).

RE: Slab on Grade Bottom Bar Location

If you are casting onto a vapor barrier, it is not on the ground; however, due to breaches in the barrier it might be "exposed to earth", so 1-1/2" is acceptable (assuming you are using No. 5 or smaller bar or wire).

If the steel is for temperature, not bending, put it in the middle of the slab.

RE: Slab on Grade Bottom Bar Location

If you have 2 layers of reinforcing steel with a PEVB on your soil beneath the slab 1-1/2" cover is adequate with sufficient cover on the top layer to permit sawcutting the slab without cutting the bars.  For example, with a 6" slab, I would use 1-1/2" sawcuts with 1-1/2" or 2" clear cover to the top layer.  For a 6" slab, I would only use a single layer of rebar.  Is there a reason for two layers?  Is this flexural reinforcing or just TS.  If temperature steel, then you might reconsider using 2 layers.

Dik

RE: Slab on Grade Bottom Bar Location

(OP)
There are 2 layers of bars in an interior 8" thick garage floor for tanker trucks.

The detail appeared odd with the bottom bars up 3".

The CRSI manual was showing 2" cover top and bottom, but that generated the question on the ACI requirement.

RE: Slab on Grade Bottom Bar Location

ACI specifically excludes itself for the design of SOGs under the scope section.  Depending on the building use, the mid-depth of the slab is usually a good place for the reinforcement.

RE: Slab on Grade Bottom Bar Location

Teguchi...

I tend to place the reinforcing nearest the top as noted.  Visible cracks form on the top surface and become less noticeable with the rebar closest to the visible surface.

Dik

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