I've looked around for different types of [concrete pump][1]s and simply don't know if there are many different types, what their mechanisms are and which ones are the most predominant ones.

What I've found:

* This [video][2] explains how a pump with an S-shaped tube operates.
* The [relevant wikipedia page][3] explains another type, which does differ in the way how the concrete is released

![An example of a concrete pump][4] (*a concrete pump*)


  [1]: http://en.wikipedia.org/wiki/Concrete_pump
  [2]: https://www.youtube.com/watch?v=dgmRN3BDE4E
  [3]: http://en.wikipedia.org/wiki/Concrete_pump
  [4]: https://i.sstatic.net/l9sDNm.jpg