Strong foundation is foundation of everything lol
Sometimes there are issues you could have never thought about. For example there is a certain type of gravel that is better for laying concrete than the others. it depends on composition and i had to struggle quite a bit until i got the one that is needed.
After seeing the pile i understood that choice to hire the guys was a good one, mixing and carrying concrete with the cart myself would have been an overkill considering the premium I've paid the guys was not that high.
Every job is much easier with the right tools. They just pour water, cement and feed the gravel into the machine and it transports ready concrete to the room.
Initially they have laid some insulation material on the floor, then a layer of water proof plastic, on top they have put steel net to make the construction stronger and after feeding the concrete evened it out. Also they have put expansion line around the perimeter since concrete is bound to expand and contract depending on humidity of the conditions. So i have been told, or it was just something a little bit extra to charge for :)
The job was finished in no time and definitely looked like things are becoming prettier. I will have to wait a week or so for concrete to harden and then can move on with erecting frame for dry walls.