Research On Cohesion-Adhesion And Phase Transition Of Asphalt Binder And Their Influence On Mixture Properties

Asphalt is commonly used as a binder in pavement engineering to bond loose aggregates together and form a strong overall structure.It is a typical viscoelastic material that exhibits high-temperature sensitivity and phase transition characteristics over a wide temperature range.Although the aggregate itself is an inert material,the temperature sensitivity of asphalt also affects the phase transition characteristics of the multiphase complex asphalt mixture,thereby influencing pavement performance at high and low temperatures.However,current evaluation indexes for asphalt performance do not adequately reflect the cohesion-adhesion and phase transition characteristics of asphalt,which can lead to early diseases,such as spalling,cracking and rutting.Therefore,evaluating asphalt pavement performance based on these characteristics and studying the evolution and correlation of asphalt and asphalt mixture performance during service are crucial for selecting and applying asphalt pavement engineering materials.Using surface free energy theory,the cohesion and adhesion properties of asphalt were systematically evaluated,and a correlation analysis with conventional cohesion indexes was conducted.A correlation was observed between the viscosity index and cohesion index,both of which can reflect the cohesion property of asphalt.However,no correlation was observed between the viscosity index and adhesion work index,and viscosity cannot reflect adhesion between asphalt and aggregate.Adhesion work for asphalt and aggregate with wet and dry conditions is notably different and has no correlation.Hence,we proposed the AWI index,which comprehensively reflects asphalt cohesion and adhesiveness based on cohesive work and adhesion work indexes and humidity coefficient as a parameter.This index evaluates the compatibility of different asphalt and mineral aggregates and the cohesion-adhesion in different rainfall areas.Using the dynamic mechanics analysis(DMA)method,the phase transition characteristics of asphalt were studied.The influence of test parameters on the dynamic mechanical response of asphalt was investigated,and a phase transition temperature prediction model based on heating rate and load frequency was established.The temperature scanning test method of dynamic mechanics of asphalt and the evaluation index of characteristic temperature and characteristic modulus of phase transition were determined to evaluate asphalt performance at high and low temperatures.A multilinear function relationship between the characteristic index of phase transition and the content of four components of asphalt was established.The characteristic temperature and modulus of phase transition of asphalt was effectively predicted on the basis of the content of these components.The phase transition characteristics of asphalt mortar and mixture were evaluated by using the DMA method.The evaluation methods and indexes for asphalt mortar and mixture phase transition characteristics were determined,and the influence of asphalt phase transition characteristics and cohesion-adhesion properties on asphalt mixture performance was revealed.The low-temperature performance evaluation results of asphalt mixture are consistent with those of asphalt and asphalt mortar.Asphalt quality is the main factor determining the low-temperature performance of asphalt mixture,and the addition of mineral aggregate particles has a more obvious effect on the high-temperature performance of modified asphalt mixture.A quantitative evaluation method for cohesionadhesion damage of asphalt mixture was proposed on the basis of the change value of phase transition temperature and residual modulus RM of immersed and not immersed asphalt mixture.Research on the performance evolution law of aging asphalt and asphalt mixture in service was conducted.The evolution characteristics of asphalt service performance were studied by simulating thermal aging,ultraviolet aging and natural weather aging.A functional model between asphalt performance index and aging time was established,and the evolution law of asphalt service performance was revealed.Using the full-scale accelerated loading test loop platform,the phase transition characteristics of the pavement surface mixture in service under different load cycles were evaluated by using the DMA method.The evolution law of the service performance of the pavement surface mixture under accelerated loading was revealed by establishing the function model of phase transition temperature,characteristic modulus performance index and load times.The multiple linear function relationship between the cohesion-adhesion index and phase transition characteristic index of asphalt mixture and the phase transition characteristic index of asphalt mixture was established,and the mechanism of service performance evolution of asphalt mixture was revealed.In summary,the evaluation methods and indicators for asphalt cohesion-adhesion and phase transition characteristics are determined,and the influence of asphalt on the phase transition characteristics of asphalt mixture is revealed.The functional relationship between asphalt performance index and aging time,and the relationship between asphalt mixture phase transition characteristic index and load times are established.The evolution law and correlation of asphalt and asphalt mixture service performance are revealed,providing a basis for improving the asphalt pavement performance evaluation index system and predicting the residual life of pavements.