In article , "** Frank **" wrote:
Contractors and DIY use groovers or saw cut control lines so that the
concrete will break at the joints. That's the plan but more lightly the
concrete slab will crack everywhere except at the joint lines. For the
concrete slabs I saw on patios, driveways and sidewalks, it seems pointless
to have control joints. Expansion joints excepted, off course.

So the question is, when concrete cracks then how do you make it break at
the control joints more often than elsewhere?

It really depends on the specific situation but in general terms:

1. Prepare a proper foundation for the pour. If you pour concrete
on dirt, it'll likely crack all over the place.

2. Add steel mesh and/or rebar to each slab.

3. Use the appropriate mix and provide it with an opportunity
to cure properly (pay attention to temperature and moisture
levels).

4. Agitate and otherwise ensure a complete lack of large air
or water bubbles within the concrete itself (esp, around
any steel reinforcement).

If you do those things right, correctly sized slabs will not
crack.

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