Experiment At Different Mixing Velocities And Workability Index Of Asphalt Mixture With Different Bitumen

Mixing workability of asphalt mixture refers to the ease of mixing asphalt mixture,which is related to the quality of the asphalt mixture and the construction quality,the service level and life of the pavement.At present,the research on the workability of asphalt mixture is mostly abstract qualitative evaluation,there is no workability index based on the mechanics theory.In this paper,six kinds of asphalt were selected: 70# base asphalt,SBS modified asphalt,rubber modified asphalt,Evotherm worm-mix asphalt,ACMP-1 worm-mix asphalt,ACMP-2 worm-mix asphalt,the rheological properties of various asphalt were analyzed by the Brookfield viscosity test under variable temperature and variable speeds.Under conditions of different mixing temperature(T=140、150、160、170、180℃)and different mixing revolution rate(V=20、30、40、50r/min),mixing active tests has been conducted to six kinds of AC-13 C mix.Test results indicate that according to the mixing P-V rheological diagram of asphalt mixture,mixing power P has high linear correlation with the mixing rate V,the asphalt mixture mixing flow characteristics meets the linear viscoplastic Bingham model,whose constitutive equation can be expressed as P = F +λ? V(intercept F for mixing internal plastic limit of asphalt mixture,slope λ for generalized viscosity of asphalt mixture).Then the influence factors of liquidity of asphalt mixture are analyzed,the analysis results show that the inner plastic limit F is rarely affected by temperature but affected by the asphalt type,and inner plastic limit F of mixture mixed with high cohesive asphalt is higher.The inner plastic limit F mainly depends on internal friction angle φ.With the increasing of temperature,generalized viscosity λ decreases logarithmically,and generalized viscosity is linearly related with asphalt viscosity,which shows that asphalt viscosity is the key decisive factor of generalized viscosity of the mixture.Finally,according to the principle of the mixture viscoplastic flow,this paper puts forward and defines the workability index of asphalt mixture as the percentage of reciprocal of generalized viscosity.The workability index increases with the temperature,and they are nearly linearly related with each other.Through the study of workability index,this study provides a theoretical basis and methods for determining the reasonable construction temperature of asphalt mixture.