Exterior slab on grade expansion joints

[StrEng007]

Does anyone know of specific design criteria, technical notes, etc. for the design and placement of expansion joints used in slab-on-grades?

I'm NOT referring to contraction joints/control joints used to provide a pre-determined crack location. I'm referring to expansion of exterior slabs that experience thermal fluctuations.

 

[cliff234]

Most of the structures I designed over the past 40 years had slabs-on-grade. Some were pretty big buildings with EJ's on the supported floors. None of them had expansion joints in the slab-on-grade.

 

[StrEng007]

I'm referring to exterior slabs that are large in area and don't have any building structures.

 

[Enable]

Generally SOGs that undergo thermal swings should have an expansion joint wherever they abut (existing) permanent features or anything that will provide a significant form of restraint (ready mix practice note here). Similarly, a significant change in aspect ratio might merit an expansion joint. Perimeter joints are almost always some form of asphalt impregnated fiber board to the top, which can be used in the field of the slab as well but that gets a bit difficult with most things larger than a sidewalk. OPSD has a detail for the in-field joints (link here and snip below). I'm sure your equivalent DOT will have similar.






I'm sure there's a more definitive technical note somewhere on this but it's never been a big enough thing for me to dig into it too deeply. Above is probably what you already knew but at least you now have a detail to go by. I did happen to find this maintenance manual by AECOM in a quick google search and on page 35 they note that major highways in the UK omit expansion joints. So there's that.

 

[TRAK.Structural]

Unless one of the circumstances that Enable lists above are present, you may only need construction joints to limit the pour areas and reduce cracking from drying shrinkage.

 

[dik]

The depth of the caulk should be about 16mm, else the caulk will likely fail. Check with caulking material suppliers for the type of caulk to use. You can use ethafoam 'rod' as a bond breaker between the caulk and the expansion joint filler.

 

[HTURKAK]

The following para. is copy and paste from a construction specification . The proposed EJ location for every 10.0 m could be conservative since this spec is for concrete pavement at a KSA process plant .

 

[dik]

The proposed EJ location for every 10.0 m could be conservative

Not necessarily... what is the thickness of the slab... if less than 150mm then 6m might be in order.

 

[Tomfh]

I don't specify them however the designs I see with large external concrete areas (eg hundreds of meters of 150 or 200 thick slab) are typically further apart than 6m or 10m. That seems very close to me for full depth expansion joints.

 

[dik]

Sorry... not full depth... just control joints.

 

[HTURKAK]

Not necessarily... what is the thickness of the slab... if less than 150mm then 6m might be in order.

Typical depth 250 mm. I remember 20 m for moderate climate zones having less thermal swings . The use of PT for SOG is a different story. EJ locations colud be at every 60 m etc.

 

[ads0221]

We did joints about every 20 ft specifically to separate different pour areas and put dowels at mid way depth to help transfer the load as well as help them settle together.

I know a quick rule of thumb is a joint between 24 to 36 times the thickness.