A new technique for three-dimensional classification of concrete is presented along the example of the spacing factor as a proof of concept. The technique is a combination of high-resolution Dual Energy X-ray micro CT combined with a set of subsequent advanced image processing steps to acquire the characteristic parameters used to describe a real porous system. Contrary to the state of the art methods of acquiring one characteristic measure to describe the porous system in a whole, the presented technique can be used to access detailed parameters of a real porous system with a direct and physical adequate correspondent in a three-dimensional volume.