Concrete Pavement Joints 1

[martin888888]

Hello,

I am designing a running track as a volunteer for an elementary school. 1/8 mile oval track with a 12' wide concrete running surface (will be overlay with a poly surface down the line). The section for the track I used is a 4" thick concrete section with rebar. Would calling out construction joints every 5' and then expansion joints every 25' seem reasonable? The school is in Florida so just calling out 4" thick concrete section over compacted sand subgrade.

Any thoughts?

Thanks

 

[Ron]

martin888888....be careful with specifying only 4 inches of concrete. Your subgrade will have to be extremely flat. The loading is irrelevant, but the constructability and shrinkage will control. I would also not reinforce the slab, unless you can carefully control the placement of the rebar.

Your joint pattern will lead to more cracks. For a 12' wide slab, I would place CONTROL joints (not construction joints) every 10 feet by sawcutting. The sawcuts must be done the same day as concrete placement, no matter how late that might make the finishers stay. You will only need an expansion joint about every 150 feet. Let your expansion joints also serve as construction joints.

Specify a flatness tolerance for the slab since you are using it as a running track. You do not want undulations in the concrete that will create high/low spots. Also specify a surface finish compatible with the expected surfacing to be applied, likely a light to medium broom finish.

Next, use the largest aggregate you can for the placement. Do not allow a pump mix if you can help it....for small projects such as this they will want to use a small pump which requires smaller aggregate, more cement and more water. Keep the water-cement ratio to no more than 0.55, preferably lower.

Don't compromise the concrete mix quality. Make sure they submit a mix design for approval prior to placement. Review it carefully for the properties noted. If you are in Central Florida, be careful of the aggregate source. If you get aggregate from the Brooksville area, it can have some reactivity which causes pop-outs. Doesn't happen all that often, but can and if it happens on your job, you'll regret it!

 

[DETstru]

For what it's worth, I've almost exclusively seen running tracks constructed on asphalt, not concrete.

 

[rowingengineer]

I would also want to know what the skink/swell properties of the soil are, as generally these running tracks need to be somewhat flat and controlling movement of clays can be an issue.

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