Expansion joints every 60 feet or less in my experience. Also
needed at change of dimension, use, and to prevent locking a slab.

Construction joints are for your convenience to give yourself
manageable pours. They can be directed by architect or dictated
by the equipment being used. Greased or sleeved slick dowels,
load transfer plates, and keyway will all work. The plastic
sleeves fastened to the forms sure beat drilling and fighting
dowels. None of them will make up for poor subsoil preparation
and compaction. All will require high concrete strength (14 or
more days) before loading

Saw joints (contraction joints) need to be cut as soon as you can
get on the concrete without raveling. Depending on temperature
and humidity conditions, you might chance waiting to the next
morning, but concrete will usually have decided where to crack by
then.
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______________________________
Keep the whole world singing . . . .
DanG (remove the sevens)




" Frank" wrote in message
. ..
For a 4" concrete slab, how long of a run before an expansion
joint is necessary? 50', 100'?

At the expansion joints, what is the best way to maintain the
two separate slabs on the same level over time. Dowel and sleeve
or keyway (tongue and groove)?

For cutting of the control joints, I hear within 24 hours
(green) and also 10 days ("cured") after the pour. So what is
the best time to cut the control joints and why is this timing
so important?