A concrete printer!

This is cool looking, a giant 3D printer that uses concrete.  Looks like the original author plans to sell the device in a few months.  I understand all the basics of the machine but…how to get the concrete to hold up while layering and how its not solid while its still printing baffle me.

http://hackaday.com/2014/05/29/man-builds-concrete-3d-printer-in-his-garage/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+hackaday%2FLgoM+%28Hack+a+Day%29

http://betabram.com/index.html