Hi @idgi ,
Are you using V-ray 3.4? If so, check preset materials that V-ray provides: Concrete Materials
You can also check these websites for textures and V-ray materials: Vismats.com and Sketchuptexture.com
Check this website for vast amount of textures to create material the yourself: Textures.com
“Bump map” parameter defines those kind of irregularities and make it look like ‘bumpy’ in render (not changing actual geometry).
Check this video tutorial: How to Create REALISTIC Materials