Review on constitutive models of road materials

Road material constitutive model is the essential condition of pavement structure design, calculation, and maintenance decision. Experts have conducted in-depth studies on the problems and proposed many meaningful constitutive models. However, these constitutive models have not been summarized and no uniform conclusion on the applicability of them is reported in the academic circle. The linear elastic model based on Hooke's law is still used in pavement structure design. This paper systematically reviewed the existing constitutive models that reflect the materials' mechanical properties and used for pavement structure calculation. These constitutive models were divided into three categories: linear, nonlinear, and damage models under repeated loads. The applicable conditions, parameter determination methods, advantages, and disadvantages of each model were introduced. Moreover, the model's feasibility in structural design and calculation was analyzed. Follow-up studies should focus on the parameter determination standard of viscoelastic constitutive models, the extension of the 1D constitutive model to 3D state, and the nonlinear constitutive models related to stress-strain state to drive the application of the constitutive models in pavement structure calculation and design. Furthermore, to evaluate the life cycle service performance of road materials and structures, establishing the pavement damage model from the structure perspective will be the future direction.