Exterior Slab Design
Exterior Slab Design
(OP)
I have a project where I have been requested to provide additional services for design of a few exterior slabs. The slab is to be located on a project where I am the EOR. The project is located in the northeast and the slabs are to utilize radiant heat to reduce the need for clearing of the snow. From my understanding, the heat is only used when a snow storm is coming.
Slab one is 15’ wide x 60’ long and is to be located next to a garage. This is an area that I am not too worried about as the loadings are low and the slab is relatively small. Slab two is 95’ wide x 100’ long and is to support small aircraft (less than 42,000 lbs). I think I have the design pretty much covered using the book “Designing Floor Slabs on Grade” by Ringo and Anderson, however, I am a little concerned in regards to the details.
I intend to use a 5,000 psi air entrained concrete mix (to help against the freezing temperatures and the inevitable deicing chemical that might find their way onto the slab). I am also considering splitting the larger slab into 4 different sections roughly 42.5’x50’ to help deal with expansion and contraction (I might split it up even more as I move into the final design).
Is there any input one might have for a project like this?
This is a part of the project that was excluded in my initial proposal and I have gone “kicking and screaming” into.
Slab one is 15’ wide x 60’ long and is to be located next to a garage. This is an area that I am not too worried about as the loadings are low and the slab is relatively small. Slab two is 95’ wide x 100’ long and is to support small aircraft (less than 42,000 lbs). I think I have the design pretty much covered using the book “Designing Floor Slabs on Grade” by Ringo and Anderson, however, I am a little concerned in regards to the details.
I intend to use a 5,000 psi air entrained concrete mix (to help against the freezing temperatures and the inevitable deicing chemical that might find their way onto the slab). I am also considering splitting the larger slab into 4 different sections roughly 42.5’x50’ to help deal with expansion and contraction (I might split it up even more as I move into the final design).
Is there any input one might have for a project like this?
This is a part of the project that was excluded in my initial proposal and I have gone “kicking and screaming” into.






RE: Exterior Slab Design
DaveAtkins
RE: Exterior Slab Design
Are you providing top mats of rebar? Area of steel > 0.05?
One thing that comes to mind, if you are doing radiant heating (i have never done this exterior... Fun!). Anything you do now that has a cost increase will save the owner far more money when it comes to life-cycle and this is an expensive slab, you do not want to jack-hammer it if you get spalls or excessive cracking. Ounce of prevention type deal :)
RE: Exterior Slab Design
I would divide your 15'x60' into 15'square panels. The 95'x100' would be divided into roughly 5x5 or 6x6 spaces. The 42.5'x50' would be divided into 3x3 panels.
I normally don't use dowels at joints, but, because of the electrical/mechanical components, I'd consider using dowels.
I'd use Dow Hy 60 or some type of extruded load bearing polystyrene (Type 4) under the slabs, and also 6 mil PEVB. between the insulation and compacted granular fill.
5000 psi may be a tad high, and would likely use 4000 psi, but, 5000 is better. Corrected: 30 MPa (what I would use) is actually about 4500 psi... so 5000 is on the mark.
Timing for sawcutting joints is critical. and I would fill the sawcuts with an appropriate joint filler to reduce water penetration.
Added: I have a problem with epoxy coated bars and would likely rely on a sealer with 2" concrete cover. You can also use HDG bars (a little pricier). You can tighten up any cracking with going to more than basic TS reinforcing. Spacing of sawcuts and timing will likely accommodate a regular rebar content. Your wheel loading is likely to be low and not much fatigue; loading may be 'channelised'.
Dik
RE: Exterior Slab Design
RE: Exterior Slab Design
Any reinforcing in the slab is there for shrinkage and not strength (it is also being used for the radiant heat system). I am not in charge of selecting the radiant system, but I believe they are going in the opposite direction of the electrical system.
RE: Exterior Slab Design
Dik
RE: Exterior Slab Design
Added: 60 psi would likely work with your wheel loadings.
Dik
RE: Exterior Slab Design
RE: Exterior Slab Design
RE: Exterior Slab Design
Added: XR250: with a little care, sawcutting should not be an issue.
Dik
RE: Exterior Slab Design
RE: Exterior Slab Design
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Exterior Slab Design
Great publication from 40 years ago... have used if for lots of runways and taxiways... really handy. I have a copy of the original calculations by Packard for his Hankel solution... I picked up a copy of his original paper and never had the time to 'sort it out'.
Have used PCA's 'Airport' program for numerous slabs for wheel loading and rack loading. Have a 5-1/4" disc with a copy on it, and have a couple of 5-1/4" drives, but no means of interface. Airport was a great program and one of the most useful ones.
I cut my original publication apart so I could scan it.
Dik
RE: Exterior Slab Design
IPRF Best Practices
FAA ACI 150
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.