A subject of the invention is a mixture comprising in proportions by mass:from 0.4 to 4%, preferably from 0.8 to 1.7%, of materials in the ultrafine particle size range, constituted by particles with a D90 smaller than 1 μm and / or with a specific BET surface area greater than 6 m2 / g;from 1 to 6%, preferably from 2 to 5%, of Portland cement;from 8 to 25%, preferably from 12 to 21%, of materials in the fine particle size range, constituted by particles the D10 and the D90 of which are comprised between 1 μm and 100 μm and with a specific BET surface area of less than 5 m2 / g, different from the cement;from 25 to 50%, preferably from 30 to 42%, of materials in the medium particle size range, constituted by particles the D10 and the D90 of which are comprised between 100 μm and 5 mm; andfrom 25 to 55%, preferably from 35 to 47%, of materials in the larger particle size range, constituted by particles the D10 of which is greater than 5 mm.The invention also relates in particular to premixes, concrete compositions and associated objects made of hardened concrete, as well as their preparation methods.