Performance Research Of Micro-and Nano-modified Asphalt Binders And Mixtures

The main factor affecting asphalt pavement quality and life is the distress of asphalt pavements. The research of modified asphalt binder is to improve the quality and life cycle of asphalt pavements. Due to the special characteristics of micro-and nano-materials, these materials have been applied to most areas around the world. In this study, five kinds of micro-and nano-materials (carbon microfiber, polymer modified nanoclay, non-modified nanoclay, nanomer I44P and nanosilica) were selected to blend with the control asphalt binder. The carbon microfiber (MCF), polymer modified nanoclay (PMN), non-modified nanoclay (NMN) and nanomer I44P (NI.44P) were added into the control PG58-34asphalt binder at concentrations of2%and4%; the4%and6%nanosilica was added into the control asphalt binder. The SuperpaveTM binder tests were employed to evaluate the characteristics of the control and modified asphalt binders. Rheological properties of control and modified asphalt binders were analyzed by the tests, such as rotational viscosity (RV), dynamic shear rheometer (DSR) and bending beam rheometer (BBR). In addition, properties of control and modified asphalt binders after the short-and long-term aging process were analyzed, with the aging process simulated by rolling thin film oven (RTFO) and pressure aging vessel (PAV). Based on the DSR test data, the energy dissipated per load cycle of control and modified asphalt binders was examined to better understand the rutting and fatigue resistance properties of asphalt binders. The field emission scanning electron microscope (FE-SEM) was used to observe the microstructures of control and modified asphalt binders, as well as the structures of modifiers and their distributions in the asphalt binder matrix. The Fourier transform infrared spectroscopy (FTIR) was conducted for analyzing the ratio changes of chemical bonding in the control and modified asphalt binders. Compared to the ratio changes of chemical bonding between the control and modified asphalt binders, it is concluded that the added modifiers (MCF, PMN, NMN, NI.44P and NS) in the control asphalt binder have the positive effect on the anti-oxidation of asphalt binders. According to the SuperpaveTM specifications, the prepared asphalt binders were blended with aggregates and the asphalt mixtures were compacted using the Superpave gyratory compactor (SGC). After the preparation of asphalt mixtures, performance tests of asphalt mixtures were employed to assess the properties of control and modified asphalt mixtures including dynamic modulus, asphalt pavement analyzer, flow number, indirect tensile tests. In addition, the BBR test of asphalt binders was simulated using discrete element method (DEM). Based on the test data of asphalt binders and mixtures, the following conclusion can be drawn:1) High-and low-temperature performance, and rheological properties of micro-and nano-asphalt bindersBased on the rotational viscosity and dynamic shear rheometer test results of control and modified asphalt binders, the addition of MCF, NMN and NI.44P into the control asphalt binder caused the improvements of viscosity and complex shear modulus of modified asphalt binders. With the addition of PMN and NS into the control asphalt binder, the viscosity and complex shear modulus of modified asphalt binders decreased. According to the BBR test data of control and modified asphalt binders, the creep stiffness of micro-and nano-modified asphalt binders slightly decreased with the addition of MCF, NMN, NI.44P, PMN and NS into the control asphalt binder. However, the PG grades of micro-and nano-modified asphalt binders were almost the same as the control asphalt binder. Therefore, the low-temperature performance of micro-and nano-modified asphalt binders did not degrade significantly.2) Microstructure and chemical analysis of micro-and nano-asphalt bindersAccording to the SEM and FTIR test results of modifiers, control and modified asphalt binders, the material structure and dimension of modifiers (MCF, PMN, NMN, NI.44P and NS) were observed, and the ratio changes of chemical bonding in the control and modified asphalt binders also were obtained. The addition of MCF, PMN, NMN, NI.44P and NS into the control asphalt binder can delay and weaken the aging and oxidation effect of asphalt binders.3) Performance evaluation of micro-and nano-asphalt mixturesThe performance tests (dynamic modulus, asphalt pavement analyzer, flow number, indirect tensile tests) of asphalt mixtures were carried out. The test results show that the dynamic modulus, flow number, resilient modulus, dry tensile strength and rutting resistance of micro-and nano-modified asphalt mixtures were significantly improved with the addition of MCF, PMN, NMN, NI.44P and NS into the control asphalt mixture. 4) Discrete element simulation of bending beam rheometer testThe three dimensional bending beam was created by the discrete element method to simulate the bending beam rheometer test. Based on the BBR test data, the input parameters of DEM model were obtained and the DEM model was also calibrated and validated. Then, the BBR simulation work of asphalt binder was conducted. According to the test and simulation results, the stiffness values of the simulation and test were so close when the generalized Maxwell model was applied into the DEM model.