Viscoelastoplastic Compaction Properties of Cement-emulsified Asphalt Mixture Based on Bodner-Partom Model

In order to reveal the viscoelastoplastic deformation properties and mechanism of cement-emulsified asphalt mixture, universal testing machine compaction test was employed to simulate the compaction process in combination with the construction process parameters of the pavement roller. According to the deformation characteristics of mechanical response curve under loading cycles, the effective mean stress was introduced into the Bodner-Partom (B-P) model to construct a compaction deformation constitutive model of the mixture. Through nonlinear fitting analyses of the strain-time data, the parameter values of the constitutive model in the process of load cycles were identified, and furthermore, the viscoelastoplastic rheological properties and dynamic deformation mechanism in the compaction process of the mixture were revealed. The results show that the universal testing machine compression test fully reflects the deformation characteristics of the mixture. With the increase of loading cycles, plasticity and viscoplasticity deformation of the mixture decreases, and elastic and viscoelastic deformation of the mixture increases. According to viscoplastic deformation rule of the mixture, the expression for calculation of the void fraction in the compaction process is derived, deducing the changing rule of effective mean stress with the void fraction. The changing rules of B-P model parameters are listed as follows. Viscosity coefficient η increases with the increase of the load times and indicates that viscous property of the mixture increases after further compaction process. Strain rate sensitivity coefficient n1 remains the same and demonstrates that mixture temperature in the compaction process is relatively constant. Internal validity Z and stress limit D0 show an increasing and decreasing trend, respectively, with an increase in the load times. The former indicates that the inelastic deformation resistance increases, and plasticity and viscoplasticity deformation decrease with further compaction. The latter implies that the plastic strain rate decreases and plastic deformation proportion of the total deformation decrease gradually under a single cyclic loading. In conclusion, the B-P model parameters accurately describe viscoelastoplastic rheological properties of the mixture, which are associated with time and loading cycles. It can be verified that the reconstructed B-P constitutive model can effectively reveal viscoelastoplastic deformation mechanism in the compaction process. This can provide a theoretical foundation for further research on compaction rheological performance and pavement compaction techniques of the mixture. © 2019, Editorial Department of China Journal of Highway and Transport. All right reserved.