Development of Continual Deterioration Prediction Models for Cement Stabilized Base

Cement stabilized materials (CSM) serve as the typical semi-rigid base pavement material, have been widely used as the base and subbase courses of highway structures in China. The residual modulus is a core indicator for the reflecting existing performance of CSM, and it is important basis for the structure and rehabilitation design of the semi-rigid base asphalt pavement. Therefore, this study focus on the damage accumulation process and modulus decay of CSM. Firstly, the strength and fatigue features of CSM were tested via the four-point bending (4PB) tests under various stress levels in the laboratory. Secondly, the fatigue transfer functions and their reliability models for the different types of CSM were established using the testing data. A total of eight fatigue transfer equations with different reliability of the base CSM (6% cement content) and subbase CSM (4% cement content) were fitted through 45 sets of valid test data. The fatigue resistance of the base CSM is slightly better than that of the subbase CSM. Then, after analyzing the influence law of modulus decay under cyclic loads, the relationships between residual modulus and number of fatigue load cycles were studied. It is found that the damage damage process of CSM presents typical three phases: initial change in the phase I (taking 10%-15% of fatigue life), stable decay in the phase II (taking 60%-80% of fatigue life), and rapid damage in the phase III (taking 10%-25% of fatigue life). Accordingly, this paper provides a range of parameters for the three phases of CSM fatigue damage. Finally, three prediction models for modulus decay are established, including the incremental-recursive deterioration model, three-phase deterioration model, and the MEPDG’s CSB fatigue model. These findings can be used for estimating and predicting the residual performance of CSM base, which are useful for enhancing rationality of pavement maintenance and rehabilitation (M&R) and ensuring the durability and reliability of highway structures.