Even though concrete is a ‘rough’ material, it quite often has some strong, slightly glossy reflections in places that are smooth, especially if smooth plywood is used as the form for pouring it. It is never completely smooth and shiny (unless polished), so it has this patchy look most of the time:
The Diffuse is a basic photo sourced texture.
The reflection glossiness is the most important element here. The overall reflectivity is pretty low contrast and can be made from the b&w Diffuse map, but the glossiness needs some lighter (“smooth”), patches.
The same areas that are smooth in the gloss map need to be smoother than the rest in the Bump map (or as previously mentioned, in this case, a Normal map).
