Abstract: The invention is directed to a cement composition comprising (1) 10-30% of an alkaline-earth mineral substance such as a slag or cement having a base of calcium aluminate or a calcined alkaline-earth oxide, (b) 14-56% of a constituent of a grain size of 100 A to 0.1 micron selected from silica, chromium oxide, TiO.sub.2, ZrO.sub.2 and Al.sub.2 O.sub.3, and (c) 14-56% of an inert filler of a grain size from 1 to 100 microns, the sum of (b) + (c) representing from 70 to 90% of the cement. Concrete mixtures which employ the inventive cements display superior properties.