Yeah, that concrete should be darker.
We call my second cousin Sgt. Schultz. He's a good fit for the name, I'm 9th in my class so there;s just a little contrast.
yes darker grey .. the floor needs to be way darker then the walls .. you could even try a wash > take dark grey and put some on the floor and with a cloth wipe it all over (spread it out) continue untill you get a cool effect and the floor is dark grey but a you also have little bit of light(er)area's ..
I'll try to wash it with the black I initially used and see what it does at some point. My bench is a bit crowded right now and this is stuffed up in my display cabinet.