A mixing axis (1, 2) of a dual axis mixer for concrete mix, said mixing axis comprising several mixer elements attached to the mixing axis, said mixer elements including a mixing shaft (3) protruding substantially radially from the mixing axis, and at least one mixer blade (4) attached to the outer end of the mixing shaft, so that on that section of the mixing axis (1, 2) of the dual axis mixer that is located in the mixing tank, mixer elements are attached at nine successive mixer element fastening points (A-I), so that in the first, second and last fastening point (A, B and I), the total area of the mixer blades (4, 4') connected to a single fastening point is substantially four times as large as the total area of the mixer blades (4) connected to a single fastening point in the third, fourth, sixth and eighth fastening point (C, D, F and H). The invention also relates to a dual axis mixer provided with a described mixing axis.