Study On Viscoelastic Characterization And J-mrp Prediction Model Of Asphalt Mixtures

Asphalt mixture is a typical viscoelastic material,due to the complexity of its internal structure and compositional properties,the researchers prefer to study macroscopic viscoelasticity of asphalt mixture by laboratory tests when the correlation between the internal component structure,macroscopic properties and viscoelastic parameters are not established.However,a large number of repetitive tests cause human resources,financial and time to be wasted,and the dynamic evolutionary relationships between macroscopic viscoelasticity and compositional structures are also unable to be established.Therefore,it is very necessary to study on the viscoelasticity expression of asphalt mixture,as well as the viscoelastic prediction model that take account of the compositional properties and internal structural characteristics.Firstly,based on the generalized Maxwell model and generalized Kelvin model,the discrete time spectrum was obtained by the improved sigmoidal pre-smooth fitting method,the numerical conversion methods between discrete relaxation time spectrum and discrete retardation time spectrum in multi-spatial domain were proposed,the overall viscoelastic parameters of asphalt mixture could be obtained through only one type of viscoelastic test.Taking into account the undesirable discrete time lines,the viscoelastic properties were characterized by continuous time spectra,an expression for determining continuous time spectrum of asphalt mixture was proposed based on improved sigmoidal function,a relational expression of the discrete time spectrum converted from continuous time spectrum has been established.Further,a conversion method that is more suitable for obtaining the viscoelastic parameters of the relaxation system and the creep system through the results of the complex modulus test was proposed.Secondly,the MRP model was improved which considering the heterogeneous distributing of internal components of asphalt mixture,then a uniform J-MRP model was proposed which was more convenient for engineering applications.The dynamic shear moduli of the asphalt mastic was predicted using the proposed J-MRP model.However,the predicted values were lower than the test values,the lack of considering the physicochemical effect of asphalt and mineral filler in the model was confirmed as the main reason leading to the low prediction value by the microscopic tests.Then a four-phase J-MRP model of asphalt mastic was established with actual physicochemical effects,the results showed that the predicted dynamic shear modulus of the four-phase J-MRP model was closed to the experimental values when the volume fraction of structural asphalt layer is 30%.Thirdly,based on prediction model of asphalt mastic,the J-MRP models of asphalt mortar and asphalt mixture were established through stepwise homogenization,then a progressive prediction models of asphalt mixture were established.However the predicted values were lower than the experimental values obviously,a simplified correction method considering the interaction between the aggregate and the asphalt mastic was proposed,when the embedding factor c=0.1,d=6 or 7,the predicted values of the asphalt mortar using J-MRP model were close to the experimental values,and the predicted values of the asphalt mixture using J-MRP model were in good agreement with the experimental values when c=0.1,d=7.5 or 8.Based on the viscoelastic parameters conversion methods of continuous time spectrum,the predicted dynamic shear modulus of asphalt mixtures could be converted to creep compliance and relaxation modulus,and the predictions of the viscoelasticity of asphalt mixture were achieved.Finally,the prediction process of viscoelasticity of asphalt mixture based on the J-MRP model was given,the dynamic modulus of SMA-13,AC-20 and ATB-25 were predicted,the prediction results of relaxation modulus and creep compliance were also obtained based on the conversion of continuous time spectrum,comparing with experimental values showed that the prediction and experimental results were more consistent,which further validate the effectiveness of predicting the viscoelastic properties of different types of asphalt mixtures based on the J-MRP prediction model.The prediction of the overall viscoelasticity of asphalt mixture could be achieved through the establishment of the methods of viscoelastic parameter conversion and prediction model,a large number of repetitive viscoelastic tests could be reduced,and the effect of component phase properties and internal structural characteristics of asphalt mixture on its viscoelastic properties could also be revealed,The research results in this paper can provide a scientific theoretical basis for the composition design of asphalt mixture in consideration of the microcosmic information,and play an active role in the development of the composition design method of asphalt mixture.