I love the concept, but I think the blocks would lend themselves to more expensive projects then what I would ever do personally. I do a lot of logging here and crossing streams is a big issue and I would love to have something more visually pleasing then a plastic culvert or timber bridge that rots out.
Agriculturally speaking, I always thought using inflatable bags with concrete would be the answer. Pour the concrete on the inflatable bag. Blow it up. Let it harden and then remove the bag. In very little time and money you could have a Quonset hut suitable for wintering livestock.