Research On Rheological Properties Of Asphalt Mixture Based On Multilevel Dispersion System

The mechanical response of the asphalt mixture depends on the temperature and the loading frequency under load,and it behaves as a typical viscoelasticity.It is one of the research contents of asphalt materials to study the rheological behaviors such as temperature and stress dependence of asphalt and its mixture based on rheology.According to modern mastic theory,asphalt materials can be regarded as a three-level network dispersion system including asphalts,mastics and mixtures.However,the properties of binders,mastics and mixtures are often studied independently in actual research,resulting in a disconnection of performance characterization across the scattered scales.The purpose of this paper is to study the rheological characteristics of asphalt materials at different dispersion system scales,including methods for evaluating the rheological properties of asphalt,mastic,and mixtures and their correlations,through a combination of theoretical analysis and laboratory experiments.The rheological characteristics of asphalts and mastics from high temperature to low temperature are systematically studied based on the dynamic shear rheological experiments.Simultaneously,the aging effect is also considered.The applicability of the prediction model of the dynamic modulus for the mixtures based on the properties of the asphalt and the properties of the mastics is comprehensively compared through the experimental data analysis of the dynamic modulus response of the mixtures.Part of the results of this paper can be used for the preliminary selection of raw materials,the improvement of mix design methods and the improvement of mixture performance.The main research conclusions of this paper are summarized as follows:The workability of the asphalt mixture during the construction period was quantitatively characterized from the mixing and compaction stages.To study the influence of the geometrical characteristics of the aggregate on the rheological performance of the mixture during mixing stage,an asphalt mixing rheometer was developed.The experimental results show that the mixing rheological properties of the mixture tend to deteriorate with the increase of the size of the aggregates.During mixing stage,the yield stress is most sensitive to the changes of shape index for asphalt-free aggregates;Yield stress is most sensitive to angularity changes for asphalt-containing aggregates;Yield stress is most sensitive to changes in sieve diameter for grading mixtures.In the stable mixing stage,the rheological characteristics are most sensitive to the sieve diameter of the aggregates,followed by the shape index,and rheological characteristics of mixture is less sensitive to the influence of the angularity.The energy index DCEI can characterize the compaction rheological properties of the asphalt mixture in the design compaction stage.Within the range of asphalt viscosity of 200?400c P,and the viscosity of the mastic of 1?3 Pa.s,the DCEI value shows a low peak region,which is consistent with the Stribeck theory.The rheological behavior of mixture during compaction decreases firstly and then increases with the increase of the mastic viscosity.In addition,the DCEI value shows a trend of decreasing first and then increasing with the increase of the average mortar film thickness,and the relationship between the viscosity and the thickness of the mastic with the DCEI conforms to the Gaussian formula.Applying the Stribeck friction theory to the compaction process of asphalt mixture,it can be divided into three states:boundary lubrication state,mixed lubrication state and fluid lubrication state.Comparing the applicability of the prediction model of the dynamic modulus of the mixture between the properties of asphalt and the properties of mortar comprehensively,we can know that:The prediction result of the improved Hirsch model in the prediction model of the dynamic modulus of asphalt mixture based on asphalt properties is the most accurate,followed by the Witczak 1-40D model.However,the prediction model of the dynamic modulus of the mixture based on the properties of the mastic,the|E*|predicted value is always lower than the measured value.The reason for this deviation may be that the assumptions of the micromechanical model do not match the characteristics of the actual HMA mixture.The prediction accuracy of the two models is affected by changes in factors.The prediction model of the dynamic modulus of the asphalt mixture based on the properties of the mastic is suitable for highly modified asphalt mixtures.Furthermore,both models performed well under the conditions of dense grading and appropriate filler-to-binder ratio.There is a good correlation between the asphalt/mastic G*and the mixture|E*|in logarithmic coordinates,the formula is y=a+bx+cx~2,and the correlation coefficient is above0.99.The G*-|E*|curves of different binder types and filler-to-binder ratios in the double logarithmic coordinate show significant differences,whereas the G*-|E*|curves of different grades,aggregates and fillers show slight difference.The asphalt G*-mix|E*|curve is closer to the linear correlation,while the mastic G*-mix|E*|curve is closer to the univariate quadratic equation correlation.