Preparation And Mechanism Of Ultrafine Inorganic Powders Modified Asphalt Binders

With the development of pavement technology and petroleum industry, the asphalt is widely used as the binder material in asphalt pavement. Besides the factor of the traffic loads, the more important factor which effects on the in-service performance of asphalt concrete pavement is the properties of asphalt material itself. Due to great temperature susceptivity (becoming soft and fragile at high and low temperature respectively), apt to age when exposed to the high intensity ultraviolet ray and high temperature, and inferior fatigue endurance performance, the serviceability of asphalt materials has been limited to same extent. The modification becomes an effective way to improve the performance of asphalt material. The modification applying ultrafine inorganic powders can not only improve the properties of bitumen but also lower costs to a great extent, so it becomes one of the research focuses.Firstly, Organic Montmorillonite (OMMT), Nano-CaCO₃, Carbon Black (CB) and Mineral Powder have been chosen as modifiers in the present research, then the modified bitumen have been prepared. The Rotation Thin Film Oven Test (RTFOT) and Pressure Age Vessel Test (PAV) have been conducted to simulate the situation of short-tem and long-term aging, respectively. And the dynamic shear rheology appearance (DSR) has been adopted to investigate the rheological performance of the modified bitumen. The results show that the loading of the ultrafine inorganic powder can improve the complex modulus, and also reduce the phase angle of the bitumen. Among those modified bitumen, the binder containing OMMT exhibits excellent resistance of rutting performance at high temperature, but the low-temperature performance has not been improved.Secondly, the aging resistance of the ultrafine inorganic powder modified bitumen has been researched, and the results shows OMMT modified bitumen has best aging resistance to heat -oxygen, the CB modified bitumen has also improved the aging resistance to a certain extent. But Nano-CaCO₃ and mineral powder modified bitumen have not improved the aging resistance. The modified bitumen containing 6% OMMT shows better aging resistance than 3%, but aging effect shows nonlinear increase at the same time. And an evaluation method based on the rheological parameters has been proposed to investigate the aging performance of the modified bitumen, which shows excellent relativity with the traditional residue penetration ratio.Thirdly, the stress loading mode was applied to research the fatigue performance of the modified bitumen. The comparison results show that the modified bitumen containing OMMT suggests better fatigue resistance.Finally, X-ray diffraction appearance has been adopted to characterize the microstructure of OMMT modified bitumen. X-ray photoelectron energy spectrum appearance (XPS) has been used to investigate the stability of modified bitumen. The results indicated that the structure of intercalation formed in the bitumen matrix, and have a good dispersion state. And the modification mechanism of OMMT was interpreted at the microcosmic dimension.