The Application And Multi-scale Research On Thixotropic And Aging Properties Of Mixed Asphalt Used In MA

The technology in deck surfacing of the steel bridge is a global problem, attracted great attention by both academic and engineering circles. According to the "pertinent, practicable and forward-looking" theory, this paper has paid great attentions to the mixing process of asphalt mixture, in order to solve the problem of poor high-temperature stability, cracking and other problems in the lifespan of the pavement. Also this paper has used both macroscopic and mesoscopic scales to analyze the thixotropic in the mixing process of asphalt mixture. Fourier transform infrared spectra(FTIR), gel permeation chromatograph(GPC) and atomic force microscope(AFM) is used in the micro-scale analysis. Full-scale accelerated loading test is used in the macro-scale analysis. This paper correlates the micro-scale and macro-scale to solve the key problems in the MA style pavements. This paper expounds the Super Thermal oxygen aging mechanism of MA asphalt concrete, providing basis theoretical supports to the prediction of MA materials and giving technical supports in building the long-term durable deck surfacing of the steel bridge.This paper mainly finished the following works:(1)This paper used the AR-2000 rheometer to analyze the thixotropy of the mixed asphalt, attempting to raise constitutive equations and evaluating methods of the mixture, which is of great importance to the law of the thixotropy and the deformation and flow of the asphalt. This paper is an essential basic support for the engineering application.(2)This paper used FTIR, GPC and AFM to analyze atomic forces, molecular weight distributions and functional group changes in the aging period in micro-scale. Meanwhile, this paper contrasts the micro-characteristics of asphalt aged in laborotary conditions and in the real constructing conditions, proposing ways to simulate the real short-term aging of asphalt in super hot oxygen conditions in laboratory. Also this paper has analyzed the changes of microscopic structure and the changes through time. This is a basic theory to combine microstructure scale, mesoscopic scale and macroscopic scale, providing basis theoretical supports to the prediction of MA materials and giving technical supports in building the long-term durable deck surfacing of the steel bridge.(3)Dynamic shear rheometer, Brookfield viscometer, penetration, softening point tester is used to analyze the changes of the asphalt in aging time. Dynamic parameters, penetration, softening point and other indicators are used to compare with the micro-scale index to show the super hot oxygen aging mechanism. Also, this paper has analyzed how the aging time influences the viscoelastic properties of the asphalt concrete. This paper has analyzed the mesoscopic behavior changed with the micro-scale. This can make great contribute to the indicators in microstructure scale, mesoscopic scale and macroscopic scale.(4)Using drop hammer viscometer to analyze the fluidity of the asphalt concrete, focusing on the influence law of the mixing temperature, mixing time and coarse aggregate content in different devices, which is a steady foundation of the best process, guiding the design and construction of the asphalt concrete.(5)Rutting test and impact toughness test are used to analyze the high temperature performance and fatigue performance of the MA concrete. The study is mainly about the performing difference in different preparation equipment, mixing temperature, mixing time, content of coarse aggregate. This combining with the workability test results may determine the best constructing period, providing a good reference in designing and construction of MA concrete. Also the correlation analysis of index in micro-scale and macro-scale provides basis in explaining the macroscopic mechanical behavior.(6)This study is applied to the full-scale model of steel box girder bridge deck to the accelerated loading test. This verifies the rationality of the best constructing period of MA concrete. Also, this paper has analyzed the dynamic mechanics of the MA concrete, providing basic parameter in MA concrete design and life-span prediction and comparing the difference between MA concrete and normal asphalt concrete in parameters of CAM model. Furthermore, this paper uses full scale loading measuring the rutting deformation to analyze the correlation and agreement among MA material micro-scale parameter index, meso-scale dynamic viscoelastic mechanical index and macro-scale high temperature performance index. This provides scientific evidence in long-term durable technology in deck surfacing of the steel bridge.