Mixing power measurement at different mixing velocities and mixing rheological model of bituminous mixture

In order to quantitatively evaluate the mixing workability and to deeply know the evolution mechanism of the strength of bituminous mixture, an experimental device of mixing power measurement at different velocities named V-P-Mixer was developed in laboratory based on the conventional mixing devices, and an experiment was carried out for the mixing rheological behavior of bituminous mixture.Based on AC-13C bituminous mixtures with different bitumen contents(0-8%), the mixing powers were measured at different mixing temperatures(130 ℃-170 ℃)and mixing velocities(20-50 r·min^-1), the power-velocity diagrams were analyzed, a visco-plastic mixing rheological model was presented, and the workability index was defined as the reciprocal of mixing viscosity.Analysis result shows that the alternating errors of electric current, voltage and power consumed during mixing are respectively 2.25%, 0.11% and 5%, and the repeatability error is 0.25%, so the measurement is stable and reliable to characterize themixing power of bituminous mixture; the mixing rheological property obeys the linear Bingham model, in which the straight slope represents the general viscosity of bituminous mixture, and the reciprocal of the viscosity is defined as the workability index; when the temperature increases by 10 ℃, the mixture's viscosity decreases and the workability index increases by 10%-20%, so it is easier to mix; the mixing power and resistance increase with the increase of bitumen content, and the workability index decreases by 5%-25% when the bitumen content increases by 1%;aggregate plays plastic role, and bitumen plays viscous role in the strength mechanism of bituminous mixture.