Study On The Key Evaluating Indictors Of SBS Modified Asphalt Based On Pavement Performance

SBS polymer modified bitumen has many advantages, such as better temperature sensitivity, high temperature stability, and fatigue resistance. Moreover, it can dramatically improve the pavement performance and extend the service life. Therefore, bitumen mixture blended with SBS polymer modified bitumen is widely utilized in the highway construction. In order to obtain the optimal pavement performance, it is necessary to control the key performance indicators of SBS polymer modified bitumen and comprehend the relationships between each performance indicator. The aim of this study is to systematically evaluate key performance indicators of SBS polymer modified bitumen and validate the performance of its mixture in laboratory. The key performance indicators of SBS polymer modified bitumen should have following three characteristics: 1) Indicators can reflect the properties of SBS polymer modified bitumen, and have good relationship with pavement performance; 2) Indicators can be easily measured with inexpensive, handy, and good repeatability testing equipment; 3) Indicators must have high sensitivity to the measured performance.This study can be divided into three parts: Firstly, the viscoelastic property of the SBS polymer modified bitumen was evaluated through establishing the correlation ship among multi-stress-level creep and recovery test, toughness test, and elastic recovery test. The elastic recovery was characterized with transient recovery rate and residual strain ration obtained from multi-stress creep and recovery test, and toughness indicator. The result indicates that the measuring time of 30 minutes can be recommended to conduct the elastic recovery test. Secondly, the high-temperature indicators of SBS modified bitumen, such as softening point, viscosity, and rutting factor, were systematically assessed, and then analyzed the relationship between them. Furthermore, the effect of the properties of SBS modified bitumen on the volumetric parameters and mechanic properties of bitumen mixtures blended with SBS modified bitumen were analyzed. It is found that only enhancing one high-temperature indicator of the binder is not an effective approach to improve the overall high-temperature performance of the bitumen mixture. Thirdly, the temperature sensitivity of SBS modified bitumen was investigated by using penetration index. However, SBS modified bitumen the nonlinear property on temperature sensitivity within the whole investigating temperature range. Moreover it is found that penetration index can be easily influenced by measurement error, and cannot accurately evaluate the temperature sensitivity of the binder. Therefore, it is not suggested to recommend the penetration index as main indicator to evaluate the temperature sensitivity. Finally, in order to effectively evaluate the adhesion between SBS modified bitumen and aggregate, the boiling water test and mass test were selected as evaluation methods. To overcome the disadvantage of low distinction in tradition adhesion index, the freezing and thawing treatment was added to modify mass test. According to the results of moisture damage resistance of the bitumen mixture, the modified mass test can effectively evaluate the adhesion property of the bitumen mixture.