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Dudes: Skatepark Advice Requested

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Jan

If you install joints you are creating a potential safety hazard due to the
movement at the joint.  

The WWF you are proposing will not be sufficient to control the cracking. 
Refer to ACI 302 which states that the typical wwf slab reinf is
ineffective in controling shrinkage cracks.  

Because your concete curves vertically, cracks caused by settlement will
tend to result in wider cracks.  The only way to control this is with more
reinforcement.

You will find that expansion is not a problem.  Cracking will primarily be
due to either concrete shrinkage or ground settlement.  If you want to
control the cracks you will need to install a healthy percentage of
reinforcing.  ACI 302 states that if you use at least 0.5% reinforcing that
you can eliminate the crack control joints needed to deal sith shrinkage
strain..  The same amount of cracking will likely occur but it will occur
in the form of a number of small cracks as opposed to a few large cracks. 
These small cracks should not be a safety hazard.

Finally a question.  Obviously you want a smooth troweled surface but is
specifying that it be steel troweled three times the way to go?  Is it
possible that under some installation consitions this will result in damage
to the finish and hence a reduced life of the slab finish?  Instead I would
suggest that you consider referig to ACI 301 to see how they specify a
smooth troweled surface.
 

Mark Gilligan

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