Study On The Features And Influencing Factors Of Self-healing Characteristic Of Asphalt

The capacity of resisting the loading and the fatigue life of asphalt material can have a profound effect on the performance of asphalt pavement. Cracking is one of the main failure form of pavement, the crack of asphalt material decrease the capacity of fatigue resistance of asphalt pavement. How to improve the capacity of fatigue resistance of asphalt material has always been a hot research topic at home and overseas. Many researchers have confirmed the ability of asphalt materials and asphalt mixtures to heal themselves. The self-healing properties of asphalt has a great relationship with viscoelasticity and rheological properties of asphalt materials. The service life of asphalt pavement can be increased much more if the self-healing property of asphalt materials can greatly used.This paper chose SK-70#asphalt, SK-90#asphalt, SBS polymer modified bituminous mastics SK-70and rubber modified asphalt as the four kinds of asphalt to be studied on. The dynamic shear rheometer (DSR) was used to carry out fatigue-healing-fatigue test on asphalt materials. The change law of dynamic modulus (|G*|) and phase angle (δ) of asphalt materials were studied before and after the healing period.A time scanning test was taken on asphalt materials under the two kinds of loading mode:control of stress and control of strain. The effect of healing time, the degree of fatigue of asphalt materials before healing, healing temperature, the type and attribute of asphalt materials and loading mode on self-healing performance of asphalt materials were studied. The research results showed that, under the stress control mode, the larger the selected control stress was, the shorter fatigue life the asphalt materials had; under the strain control mode, the larger the selected control strain was, the shorter fatigue life the asphalt materials had. The self-healing characteristics of asphalt materials under the two kinds of control mode:control of stress and control of strain exhibit a same regularity. The regularity is that with a longer healing time, higher dynamic modulus of asphalt materials before healing, higher healing temperature, the dynamic modulus (|G*|) and phase angle (8) of asphalt materials recovered more close to the state before loaded, the fatigue life of asphalt recovered is longer and the self healing ability of asphalt materials is stronger. Under the specific experimental conditions in this research, the self-healing properties of asphalt are better than that of SBS modified asphalt and rubber modified asphalt. The capillary tests have done on asphalt materials to study on the effect of capillary action in asphalt materials on the performance of self-healing process. The research result shows that:with a higher temperature and a longer time, the capillary effect of asphalt materials is more obviously, which coincided the relationship between the self-healing property of asphalt material and the time and temperature of healing. The text result illustrated that the process of capillary action played an important role in the self-healing process of asphalt crack.The existing evaluation indexes of self healing performance of asphalt materials were researched and analyzed in this paper. After comparing and analyzing these existing evaluation indexes, a new evaluation index which established based on the energy density ratio was proposed according to the advantages and disadvantages of the existing evaluation indexes. The research results showed that, it is relatively one-sided to evaluate the self-healing ability of asphalt materials just using single points of dynamic modulus change or of a few time of fatigue life change of asphalt material. That cannot completely reflect the materials performance after self-healing. While the evaluation index based on the energy density ratio method can better consider the dynamic modulus recovery, the change of each index of material when it is under the fatigue loading again and the ability to resistance load of material. The new evaluation index can analysis the performance of asphalt materials more comprehensive and quantify the self-healing performance of asphalt material under the test condition more accurately.Through the fatigue test and capillary test on asphalt materials, the process and mechanism of self healing of asphalt materials has been further understood on the analysis of the test results and the research of self-healing evaluation index of asphalt materials, which provide a basis for the subsequent research.