Investigation Of Asphalt Binders Rheological Properties Evolution And Key Paving Performance Under Accelerated Aging

With the widely application of various modified asphalt binders and considering the influence of complex climate and loading conditions in the service life of asphalt pavements,it is of great necessity to understand the evolution of asphalt binders’rheology and paving performance with long-term aging for helping us to better select binders and understand their performance.Thus,this work explored asphalt binders’rheology evolution and paving performance under different artificial aging methods and aging time with the combination analysis of rheology,asphalt binder’s viscoelasticity and chemical test methods.Firstly,this work conducted accelerated aging experiments to asphalt binders,including traditional laboratory oxidative aging（RTFO and 20,40,60 hours PAV aging）,weathering aging（30,50,70 days）and natural aging（100 days）.Then,asphalt binders’rheological indices were obtained by frequency sweep and bending beam rheometer tests,and asphalt binders’rheology evolution was investigated by using a combination of time-temperature superposition principle,master curves and black space diagrams.Subsequently,temperature sweep,multiple stress creep recovery,linear amplitude sweep,frequency sweep and bending beam rheometer tests were used to evaluate asphalt binders’key paving performance based on the viscelastic continuum damage theory,asphalt binder’s continuous low-temperature grading and black space diagrams.Finally,asphalt binders’chemical indices were obtained by using Fourier Transform Infrared Spectroscopy test,and the correlation between binders’physical and chemical indices were also analyzed.The main conclusions are as follows:1)The addition of SBS copolymer significantly changes binders’mechanical response and enhances binders’performance in every aspects.The most obvious phenomenon is the“plateau”inδmaster curves.The addition of crumb rubber decreases binders’complex shear modulus to some extent in high frequency range and improves binders’cracking resistance.2)Different artificial aging methods have the same influence on asphalt binders’rheological properties（e.g.Complex shear modulus,Creep stiffness and compliance）and this aging effect depends on binders’property,testing temperature and frequency.The change ofδmaster curves and black space diagrams of polymer modified asphalt binders is relatively complex with aging,however,their curve shapes are similar to base asphalt binder when reaching the critical aging time.The critical aging time are 40 hours and 70 days with respect to laboratory oxidative aging and weathering aging,respectively.3)The change of asphalt binders’rutting indices with aging is associated with modifiers’type and dosage.The alteration of R_3.2and J_nr3.2 with aging is quite complex for SR1 which SBS dosage is 3%.The maximum stored pseudo strain energy is a better definition for asphalt binder’s fatigue failure and the binder sample after 20 hours PAV aging is suggested to conduct LAS test.The evolution of asphalt binders’fatigue life is related to materials property and assumed loading strain level.The critical strain amplitude for 70^#asphalt is approximate 4.5%.There exists a similar aging effect for different asphalt binders,or more specifically,theΔT_c and G-R parameter get worse with aging.4)Weathering aging and natural environment aging are able to accelerate the formation of carbonyl group.SR2 is more resistant to traditional oxidative aging comparing to weathering aging and natural environment aging.In addition,δmaster curves,black space diagrams,G-R parameter and carbonyl index I_CA are considered to be the most feasible indices for characterizing asphalt binders’long-term aging behavior.