Termites don’t eat concrete or plastics, but they will build over it and many other products. There was a few years ago some type of foam which was filled with concrete and it always worried me as in my opinion it was just a space in which they could build a tube.
Garages are well known for termite activity, I guess when build it is the last concrete poured and who knows want went on after the pretreatment. That story for another day, but I find termites in garages often and this is not always what I find but it is interesting. Since the expansion joint is visible in the garage, this is what you look for when performing a termite inspection. Mud tubes or tunnels coming up the foundation wall into the structure, are often visible unless you have storage against the walls which most people do. So the lesson here is not to obstruct the expansion joint, better said than done since the garage is the catch all of our lives.
I recommend a yearly inspection which is free from ProBest unless it is for a sale of a home or business for termites if you live in the South or Southwest and if you notice anything that looks like mud inside the home call Professional Termite Company ASAP.