How to install expansion joints when pouring a concrete driveway?

I am going to be installing a concrete driveway. I have tore out the excisting asphalt driveway and formed up for the concrete. How do I install the expansion joints? Do you pour the concrete in one pour and then use a saw and cut the concrete where the joints need to go in? How often do they need to be placed for a 17' by 78' driveway?

The expansion joints are formed either by you putting thin wooden slats in that leave slots, or, while you are smoothing the surface, you actually shape the slots with your trowel.
Usually the individual section can be about 4' x 6', and larger if you use heavy duty steel grids to strengthen the concrete.
With your measurements I would do one down the center, and the others at 6' to 8' intervals.
Since this also depends on the quality of the concrete you'll use, you may want to double check that with your concrete supplier.
Depending on the size of the vehicles you'll be running across that, I would think that you want at least a 6" thickness, and more if the underground isn't very hard and stable. Use one to two inch gravel as a base.
I did that on a driveway 38 years ago and it is still perfect.

You normally do not cut using a saw. You use a special trowel to form a groove 1/4 of the way through while the concrete is still wet.

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Space joints properly. Space joints (in feet) no more than 2-3 times the slab thickness (in inches). A 4" slab should have joints 8-12 feet apart.

Cut joints deep enough. Cut joints 25% of the depth of the slab. A 4" thick slab should have joints 1" deep.

How to cut joints. Grooving tools cut joints in fresh concrete. Saw cutting cuts joints as soon as the concrete is hard enough that the edges abutting the cut don鈥檛 chip from the saw blade.

Cutting joints soon enough. In hot weather, concrete might crack if joints are not cut within 6-12 hours after finishing concrete. In this condition, if you don鈥檛 want to use a grooving tool to cut joints, there are early-entry dry-cut lightweight saws that can be used almost immediately after finishing. These saws cut 1" to 3" deep, depending on the model.

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A correction in termonology: An "expansion joint" is a peice of felt that you place between old concrete and new concrete (or between concrete and brick). You install it before you pour.

I believe that you were really taliking about "control joints".

I would install an expansion joint half way across your driveway, running the entire length of the drive (parallel to the drive), and then at 10-12 foot intervals across the driveway (perpendicular to the drive). It will be best if you install the joints before you pour the concrete, best using expansion joint material (available at hardware store). This can be held in place using short pieces of rebar driven into the ground and then run some tie wire through the expansion board and tie off to the rebar (keep your rebar at least 1" below finished surface). Alternately, you can drive in 2 pieces of rebar, with the expansion joint material in between them. You ca also use wood instead of expansion joint material, but the wood will end up rotting out in 5 or so years.

There seems to be some confusion here. An expansion join is installed when pouring against a vertical surface (garage slab), and at roughly 20' to 25' intervals. A "control joint is scribed into the slab with a "Scoring Tool" or a concrete saw, at 10' to 12' intervals. The intermittent "expansion" joints are set up like a form and staked into place. when pouring the slab, pour evenly against both sides of the expansion material so as not to move it from its position, If this is your first attempt at pouring concrete, you're making a big mistake. You obviously don't know what you are doing, this will be a very costly DIY project for you. Concrete has 4 simple rules:
1. It's heavy.
2, It gets hard.
3 It cracks.
4. NOBODY EVER STEALS IT.

you should put an expansion joint every 10 feet.

place a cross form at 10', pour that, remove the cross form, put a felt strip across and pour the next section, continue till finished

you can buy felt strips at home depot or lowes

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