A binder premix includes from 0.2% to 63% of a material of an ultrafine particle size category, including individual particles with a D90 value less than 1 μm and/or with a BET specific surface greater than 5 m2/g; from 8% to 63% of selected Portland cement including particles with a D90 value less than 30 μm and from 25% to 85% of a material, other than the cement, of a fine particle size category, including particles for which the D10 and D90 values are from 1 μm to 120 μm and with a BET specific surface less than 5 m2/g. A binder mix including, in addition to the premix, a material of a medium particle size category, including particles for which the D10 and D90 values are from 120 μm to 5 mm is disclosed.