your average hi-res ash floor from some building site, I forget which. can be used as its own bump map etc. at low values to help break up reflections near windows etc.
link to full size image, 5200x3900 pixels.
sharing my homemade architectural hi-res textures - for those of you who work in 3D or photoshop. they are originally made for renderings in 3D max and tile seamlessly.
uploaded with a CC license. no attribution necessary.
the full set of architectural textures that tile seamlessly here. 