Energetically modified cement (EMC) has been produced by high intensive grinding/activation of normal portland caemnet (NPC) together with 20% and 50% quartz sand. EMC concretes were compared to NPC based concrete using the k-factor concept. The k-factor for concrete with w/c = 0.60 - 0.45 was 0.7 - 0.9 for 1 day and 1.1 - 1.3 for 28 days compressive strength. k > 1 for both capillay suction, porosity, vapor diffusion and chloride permeability. For carboantion resistance k was approximately 0.55.Microstructure of EMC paste with 50 % quartz sand and w/c = 0.40 showed that the quartz was extensively ground and formed agglomerates with concrete having a high inner surface. The degree of hydration of the cement in EMC was as high as 71 % after 1 day comparted to 45 % for untreated blend. Refind pore sizr distribution of EMC versus blend means that even for equal hydration at higher ages EMC will perform better.