Variable speed mixing test and mixing flowability of asphalt mixtures

To know the mixing flowability in theory and quantitatively evaluate the mixing workability of the asphalt mixture, a variable speed mixing (VSM) test device was developed in our laboratory. Different asphalt mixtures are tested by recording the mixing power under different mixing speeds (20 similar to 50 r center dot min-1) and different mixing temperatures (130 similar to 180 degrees C) to analyze the mixing flowability. Afterwards, the mixing workability index was defined from rheological parameters by establishing the mixing flow model. The experimental results indicate that the mixing flowability of asphalt mixtures obeys the linear Bingham's visco-plastic model, which conducts two mixing rheological parameters including the mixing plastic limit and the mixing viscosity by the intercept and slope of the flow straight respectively. When the mixing temperature increases, the mixing viscosity decreases and the workability index increases, but the mixing plastic limit is not affected. With the increase of the nominal maximum particle size of asphalt mixtures, the mixing plastic limit increases and the workability index decreases, but the mixing viscosity is not affected. The asphalt becomes more viscous as the asphalt content increase, which leads to worse workability. The composition of aggregate determines the mixing plastic limit, and the viscosity of asphalt mortar determines the mixing viscosity.