I am speaking under correction here but the concrete looks like Sigershaders ?
Generally speaking they work great but I have noticed that for very large areas like the one you use here
it tends to tile a bit. Its just not the texture you want to use for such a large area.
If you watch the new 1.5 material video you will actually see how easy it is to create awesome mats now straight
from the Diffuse. Overall light is very good but for me, unfortunately the main concrete texture is lacking and it dominated the render
This is a great example of how the dominant texture has been utilised correctly
https://forum.corona-renderer.com/index.php/topic,13526.0.html
Love the design and especially the portrait.