Batching Plant (disused)

The trailer to the left looks like the classic circus lion transporter but I believe it is a disused batching plant, a machine used to mix and discharge concrete in industrial quantities.
A fully functioning set up stands a short distance away. There is probably a lay person perception of concrete being a few shovels of sand,, gravel and cement mixed up with some water and poured in a shutter (mould) to form a bridge or other structure. It is a phenomenally complex subject. Samples of the aggregate will be initially lab tested and day to day the moisture content of the raw material must be monitored so that the amount of water added to the mix can be modified accordingly. (Excess water will make the final product weaker though too dry will limit its ability to be placed and fully compacted, also weakening it) The batcher itself has calibrated scales to measure each constituent as it is introduced and the operator is usually very experienced with intimate technical knowledge of both the machine (with hydraulics, gearboxes, conveyers, switchgear, electric motors and engines) and the concrete     
As a structural component it is very strong in compression but weak in tension. Hence a simply supported concrete beam (supported at each end) will try and sag. The lower half is thus in tension and the top half is in compression. The introduction of a couple of steel bars along the bottom of the beam (still covered by 2 inches of concrete at the bottom) can resist that tension and you then have a very strong component. Conveniently steel and concrete expand and contract at about the same rate with regard to temperature. I recall our materials lecturer at college described concrete technology as being way more complex than nuclear physics. I have to take his word for it.