There are a lot of posts that talk about painting hardboard or styrene to look like concrete. I have posted my method but never showed any 'construction' photos. The method I use is not the fastest in the world but I think it gets me to the color I like. Also as shown below I can 'tone' the final color to make the concrete look as dirty as I want.
After using an awl to make expansion joints in the hardboard I start with flat black paint about 80% coverage.
When dry I use red oxide - again about 80% coverage
Next comes dark gray - almost full coverage. You can kind of see the red poking through in places.
Last up is light gray. Mist spray till you get the tone you like
The neat thing is if the color comes out to light you can mist again with dark gray. Using the dark gray and light gray you can make the concrete as light or dark as you want. You can mist with black if you want soot or use powders for stains.
Joe
