The Study Of Thermal Aging Mechanism Of Asphalt Binder

The ageing of asphalt binder is an important factor affecting the performance of roadasphalt. Aged asphalt will make the pavement performance worse. Studying thermal agingmechanism of asphalt binder, evaluating and predicting aging performance of asphalt roadprovides theoretical basis for improving anti-aging performance. In this article, basing on theassociation between micro composition and structure of asphalt with macroscopic pavementperformance, we analyze the role that the change of micro composition and structure has inthe macroscopic rheological properties and road performance.At first, we prepare modified bitumen of natural asphalt, modified bitumen of naturalasphalt after short-term aging with TFOT and modified bitumen of natural asphalt afterlong-term aging with TFOT+PAV. Having a macro performance test on prepared binder,conclusions are drawn that after aging the optimum dosage is between4%and6%, andpenetration and ductility both decrease and softening point increases. Next, carryingout IR spectra analysis, DSR experiment and frequency scanning analysis on binder beforeand after aging, conclusions are drawn that the plural shear modulus of original and modifiedasphalt before and after aging both increases and phase angle decreases, and the greater thedegree of aging, the better the high temperature stability and anti-deforming capability. Withfrequency increasing, complex modulus of modified asphalt binder increases and phase angledecreases, however, the rate of high frequency and low frequency area are different.Then, with synchronous combination of thermal analysis (DSC, TG), mass spectrometry(MS) and infrared spectroscopy (IR), thermal analysis and mass spectrometry analysis arecarried out on the asphalt binder, and we analyze the characteristics of decomposition peak ofDSC curve and the temperature range of quality loss from TG curve. Integrating todecomposition peak area with different dosage, combined with the analysis of intensity of ioncurrent, we conclude that the optimum dosage is between4%and6%. Integrating todecomposition peak of DSC curve before and after aging, peak area significantly decreasesafter short-term ageing, which illustrates performance of asphalt binder becomes more stableafter short-term aging. We can get a first order differential curve-DTG curve, from which wecan see that mass loss rate of asphalt binder has three steps of change. Comparing the peak area of un-aged, short-term aging and long-term aging from DTG curve, we get that the sizeof un-aged is biggest, short-term aging takes second place and long-term aging is smallrelatively. Finally, from the view point of thermal analysis and mass spectrometry,TG-DSC-MS has a consistency. Temperature of maximal decomposition peak, weight lossrate and intensity of ion current corresponds to each other.