Metakaolin is known as one of latent hydraulic admixtures that improves properties of High Performance Concrete. Many research works demonstrate that application of metakaolin improves properties of concrete as freeze-thaw resistance and resistance against de-icing salts with freeze-thaw cycles combination. A very important role in concrete performance in such severe environment is played by porous system and surface of hardened concrete. The new method of confocal 3D laser microscopy is applicable nowadays. The text deals with the study of this method applied on samples of concrete containing metakaolin and on reference concrete. Changes of surface layer have been observed by above mentioned method together with testing of evolution of mechanical properties of hardened concrete.