A lot of the container services will not let you fill the container with concrete, at least around here. Make sure they allow it, and tell them what you have to make sure they don't hit you with a big penalty or make you unload it in your driveway when they find it's filled with concrete.

You could have over to 10,000 lbs of concrete there. A few years back I helped a friend move 6 tons, we used a 20ft flatbed trailer, and another truck with an 8ft bed... Wasn't terribly cheap to dump it... if you can find a container company willing to pick that up for you quite possibly will save money... and the effort to unload.