Method for controlling a workability parameter of a concrete in a mixer

A method for controlling at least one workability parameter of a concrete contained in a container of a mixer with a non vertical rotational axis, comprising:

• making the container turn at at least two different rotational speeds ω;
• determining, for each of said at least two rotational speeds ω, a rotary drive torque C of the container, a value of shear stress τ of the concrete and a value of speed gradient {dot over (γ)} of the concrete according to the following relationships:
• τ=T(ω)·C
• {dot over (γ)}=G(ω)·ω
• where T and G are predetermined functions;
• determining a relationship of variation of the shear stress τ according to the speed gradient {dot over (γ)} by extrapolation and/or approximation based on the determined values;
• and
• providing an indication of the workability parameter of the concrete based on the relationship of variation,
• wherein the functions G and T are obtained by determining:
• for each concrete of a plurality of different concretes, a variation curve of the drive torque of the container containing said concrete according to the rotational speed of the container;
• for each concrete of a plurality of different concretes, a variation curve of the shear stress of the concrete according to the seed gradient of the concrete b means of a rheometer;
• and
• for each pair of concretes of the plurality of different concretes, a first point of intersection (Hi) between the variation curves of the drive torque of the container according to the rotational speed of the container for the concretes of the pair and a second point of intersection (Li) between the variation curves of the shear stress according to the speed gradient for the concretes of the pair.