So yeah, check the video below and see a really simple process of creating a tileable texture in Photoshop. I've linked the images for download below too.
Download the textures here.
Concrete doesn't have a high spec when dry so I'd tone it down if you can, maybe even create a gloss map to control the specular if you're going to use it in engine. Marmoset makes it relatively easy to manipulate the power of the specular.