That doesn't look like a very effective design to me. For one thing, all the working parts are exposed, so it wouldn't take much splashed concrete to disable it totally. For a machine like this, full bellows protection would be essential. Another fatal flaw is that there's no continuously available source of concrete. The guy seems to be mixing it a gallon or so at a time in a bowl, and pouring it into the hopper, which requires gravity to dispense it. This would get old really fast.
The only good reason to want a concrete printer would be to make really large structures, the size of houses. But this thing is not nearly big enough for that - at most it could print a (really ugly) window frame. It's hard to tell much about it from the ad - the "specifiations" are ludicrously inaccurate. With the stated nozzle diameter of .4mm, it would choke on a large grain of sand. But if it really only uses 60 watts of power, it must be extraordinarily energy-efficient (not). Most of what they have to say about it seems to have been copied and pasted from the description of a totally different sort of printer. It's hard to believe they really expect someone to send them $40,000 USD for this, but I suppose hope springs eternal in China.
For a more practical design, look elsewhere - like here for instance: http://www.engineering.com/3DPrintin...g-Machine.aspx