Hi I have raised chickens for years the two things that would concern me are #1 concrete is going to get messy fast and #2 no air can pass thru gonna get hot in the summer
I'm not saying my way is the only way but over 40 years of raising chickens and steady 90% hatch rates tells me my way is pretty good.I also build and sell incubators and the only people that have probs are the ones that can't quit messing with them is my experience
You need a temp/humidity guage.Often times we are the prob with low hatch rates.We get excited and can't leave the bator alone.Everytime you open it you lose temp and humidity which causes the membrane to dry and chicks die.Open bator as little as possible and add a wet paper towel or sponge...