Organic montmorillonite (OMMT) was obtained by reacting montmorillonite (MMT) with the surfactant cetyltrimethyl ammonium bromide (CTAB). The crystalline phases of MMT and OMMT were characterized by microscopic performance analysis using an X-ray diffractometer (XRD) and scanning electron microscope (SEM). The effects of rubber, attapulgite, columnar diatomite, and disk diatomite on the technological and rheological properties of OMMT-modified asphalt were studied using a dynamic shear rheometer, and the low-temperature properties were determined from their creep characteristics by a bending beam rheometer. The short-term, long-term, and ultraviolet (UV) aging of modified asphalt were tested, respectively. After adding five types of modifiers to the asphalt, the high-temperature rheological and aging resistance of matrix asphalt and modified asphalt can be improved. In particular, it is shown that modification with OMMT with attapulgite as comodifier had a positive influence on asphalt thermo-oxidative aging and UV aging.

Subgrade soils are often unsaturated and the resilient modulus (M_R) of subgrade soils is usually subjected to the climate environment and traffic loading in the field. Therefore, the Matric Suction (MS) and traffic loading are considered to be two important parameters associated to the M_R prediction model. To verify the M_R prediction model, the MS of the typical subgrade soil were determined through the pressure plate test. In this study, the soil-water characteristic curves were also described using the Fredlund & Xing’s model. Then, the dynamic M_R of the typical subgrade soil under various stresses and water contents was measured. After that, a new prediction model was proposed with the model variables including the minimum bulk stress, octahedral sheer stress and matric suction, and the validity of the new model was verified by previous research results. Finally, the correlations between the physical properties of subgrade soils including the percentage passing through the No. 200 sieve (0.075 mm), plasticity index, liquid limit, dry density and the regression coefficients of the new model were established. The results show that the new model can be used to predict the M_R well, and it effectively solves the problem that the bulk stress is equal with a different combinations of the confining pressure and deviator stress. At the same time, the M_R can be predicted much more easily with physical parameters of subgrade soils rather than conducting triaxial tests.

In order to reveal the effects of aging on fatigue damage evolution pattern of asphalt mixture, and to reveal the fatigue damage patterns of asphalt pavement during its service life more accurately, the viscoelastic fatigue damage model for the aged asphalt mixtures was proposed based on the Burgers viscoelastic model. The dissipation energy was taken as the damage variable, and the direct tension fatigue tests for asphalt mixture in five different aging degrees were conducted. The viscoelastic parameters of the aged asphalt mixtures were obtained.The calculationmethod of the cumulative fatigue damage was proposed, which considers the aging effects. Moreover, the critical fatigue damage degree and fatigue life calculation equations were derived by employing the fatigue damage model, which were calculated and compared. The calculation errors range from 3% to 18%, which was within an acceptable error range of 30%. The research results show that the aging has a prominent impact on fatigue properties of asphalt mixtures, which could be illustrated by the change of the parameters of the viscoelastic fatigue damage model for the aged asphalt mixtures. The prediction precision of fatigue life is acceptable for using the proposed viscoelastic fatigue damage model.

In order to characterize the ability of tension and compression deformation of asphalt mixture more truly and to improve the test efficiency and scientificity of the tension and compression moduli, the synchronous test method based on the indirect tension test was proposed. The analytical algorithms of the tension and compression resilient moduli of the indirect tension test were derived by integrating the functions of the horizontal and vertical radial strain at the center of a specimen, which was based on Hooke’s law in the two-dimensional stress state and the principle of calculus. The direct tension, unconfined compression, and indirect tension moduli tests were conducted in both dynamic and static loading states, and the test results were compared in different loading states. The research results indicated that the synchronous testing method based on the indirect tension test is effective, and there is a significant difference between the tension and compression moduli of asphalt mixture, and the dynamic resilient modulus from the indirect tension test increases by a power function with the increase of loading frequencies.

TiO₂ pillared montmorillonite (T/M) modifiers have been studied to alleviate the aging of asphalt pavement and degrade automobile exhaust, but the photocatalytic activity of ordinary TiO₂ is not good enough. In this study, in order to improve the photocatalytic performance of T/M, different metal (Ce, Cu, Fe) doped modifiers were prepared based on T/M. Metal doped TiO₂ pillared montmorillonite was prepared by the sol-gel method. The modifier was characterized by X-ray diffraction (XRD) and an Ultraviolet visible (UV-Vis) spectrophotometer. The results show that TiO₂ with different metal ions successfully entered into the layer of organic montmorillonite (OMMT) to form a pillared structure. Compared with the undoped TiO₂ pillared montmorillonite (T/M), the optical absorption edge of the metal doped TiO₂ pillared montmorillonite has an obvious red shift. In addition, the influences of the different content of modifiers on the properties of the original bitumen and catalytic capacities for automobile exhaust were also investigated. The results show that Ce doped TiO₂ (Ce-T/M) pillared montmorillonite has the best improvement in high temperature performance and ultraviolet (UV) resistance of bitumen. In the experiment of automobile exhaust degradation, the degradation law of NO and HC showed Cu-T/M > Ce-T/M > Fe-T/M > T/M. These three kinds of metal ions can effectively improve the photocatalytic degradation efficiency of T/M.