How much does a concrete mixer truck weigh?

They come in many sizes and configurations. They could be single axle trucks, tandem axle trucks, tandem axle truck with additional lift axles, tandem axle trucks with a twin steer setup (and these may also have additional lift axles, as well), and even tractor-trailers with mixer trailers. You'd have to be a little more specific as to which one you had in mind.