Investigation on strength and fatigue performance of cement-stabilized macadam under three-dimensional stress state at different ages and cement dosages

The mechanical performance of cement-stabilized macadam (CSM) is affected by the dosage of cement and age, while strength and fatigue life are two important mechanical indicators in pavement structure design. This study conducted uniaxial compression, four-point bending, indirect tensile strength, and fatigue tests on CSM, considering various cement dosages and ages. Equivalent stress was used to characterize the strength under a three-dimensional (3D) stress state. On the basis of the results of strength tests, the strength model parameters under 3D stress states were calculated. The characteristics of the tensile meridian, compression meridian, and the failure envelope surface under different conditions (different cement dosages and ages) were comparatively analyzed. The fatigue life data were processed by using the Weibull function and reliability theory to eliminate the dispersion. And the relationship between fatigue life and three-dimensional fatigue stress ratio (Delta) was established. It turns out that the tensile meridian of CSM with older ages is above that of younger ones, and the same rule applies to the compression meridian. The failure envelope surface of CSM exhibits variations in both shape and size under different conditions. As the cement dosage and age increase, the failure envelope surface expands outward. The fatigue life curves under the three stress states processed by the Weibull function are very close and can be uniformly characterized. The fatigue life of CSM with 4 % cement dosage is more sensitive to Delta than at other cement dosages, which with an age of 28 days changes faster with Delta than that with an age of 90 days in the study. This work reveals the strength and fatigue characteristics of CSM under the 3D stress state at different cement dosages and ages. The findings serve as a valuable reference for the design of CSM base layers in diverse conditions.