My house is 6 years old. In my driveway and backyard patio, the expansion joint in the concrete has come out in several places. This has left a gap of about 1/2 inch wide. How do I fill these gaps. I checked with home improvement stores and they don't have any good solutions. I have three options: 1. Mix new concrete and fill in the cracks. I am concerned about concrete cracking during summer. 2. I can fill in the gaps with concrete crack fill. This is very expensive and perhaps not a long term solution (may crack again). 3. I can fill in with new expansion joint. Not sure how to secure these in place. Can you help please.
Regards
Mohsen

You don't want to fill in these areas with concrete. These are like you said expansion joints.
The best thing to do is put back in joint material. They have this at home centers. It's a homosote type of material.
Clean out the joint with a screw driver and wet vac and put a piece back in.
To secure in place, apply silcone adhesive before installing.
There is a chance that the joint material over time will pop back out. Then you may need to put flexible concrete sealant in the joint.