Unified fatigue characteristics model for cement-stabilized macadam under various loading modes

Cement-stabilized macadam is widely employed as a base-layer of pavement in China, because of its high strength and stiffness. However, fatigue cracking of the cement-stabilized macadam based pavement is prone to occur under multiple traffic loads, which affects the service life of the pavement. The main objective of this work is to reveal the fatigue characteristics of cement-stabilized macadam under various loading modes by developing a unified fatigue characteristics model. To this end, an unconfined compressive strength test, indirect tensile strength test, and four-point bending strength test were conducted for the cement-stabilized macadam samples under various loading rates. A power function was employed to the pattern of variation of strength with loading rates. The stress ratio of the fatigue test associated with the loading rate was obtained and defined as the rate-dependent stress ratio. Also, the fatigue tests under various loading modes were implemented based on the rate-dependent stress ratio and nominal stress ratio. The preliminary laboratory experimental results showed that it is challenging to compare fatigue performance under different loading modes based on nominal stress ratio. However, the problems of uncertainty and non-uniqueness of fatigue characteristics under various loading modes were resolved by employing the idea of rate-dependent stress ratio in the correlation analyses. Based on that, the new strength structure coefficient associated with the loading rate was proposed in this study. Therefore, the proposed research results provided the fundamental understanding of the fatigue resistance design of pavement with semi-rigid base-layer