I'll think you find that it's a concrete mixer (truck) although in my experience they don't conduct any actual mixing. The mixing is carried out at the depot and the truck just keeps it moving so as not to allow it to "go off". When I was working on the M62 Scammonden in the early 70s there was an over order on a bridge pour (which is normal). There was a new guy on the surplus truck and he was told to go get rid to a local farmer. Being an enterprising young lad he tried to sell it to the farmers. Now farmers in Yorkshire are canny folk and they know that he'll have to give it away eventually. Unfortunately by the time the driver concluded that, the drum was full of solid concrete.