Yep, our constructions are a little bit heavy.
On the top of my garage we used 12m³ of concrete (FCK = 20MPA).
I don't have the exact weight for 20mpa concrete, but the specs of 18mpa it's 2306,88kg.
12 x 2306,88 = 27.682,56 kg.
Yeah, it's a little bit heavy... lol