Concrete expansion joints are important to install on stationary objects that your concrete will be up against. Some examples of such stationary structures are: a house, a building or deck posts. If you do not install expansion joints on permanent objects, you will risk damaging the concrete or the permanent structure the concrete is up against. There needs to be a source of movement because of the freeze/thaw cycle that is common in environments such as Minnesota.
You can purchase expansion joints at a home improvement store in various sizes. For the four inch patio we are pouring here, we bought 4 inch width expansion joint and enough to cover the sides of the house and deck posts.
If the structure your concrete is up against is wood, you can nail or screw the expansion joint to the structure (pictured above), if it is not, just lay the expansion joint up against the structure and make sure that as you pour the concrete the expansion joint remains flush with the structure and does not fall forward into the concrete. Here is a picture of expansion joint up against a concrete structure. We just set it up against the concrete with the fill dirt helping to keep it stable:
Does pouring your own concrete sound too complicated? If so, and you live in the Minneapolis and surrounding suburbs area, request a quote on your project.