Multi-scale Research On Water Stability For Various Aging Procedures Of Warm Mix Asphalt Mixture

Warm mix asphalt(WMA) is a green pavement construction material which is helpful to energy saving in addition to minimizing the emission of greenhouse gas. There is a greater challenge for its moisture susceptibility because the construction temperature is cut down. Therefore,how to improve the water stability of warm mix asphalt mixture has become a problem that the engineering department must be considered and solved urgently. However, it was found in the research of warm mix asphalt water damage that water stability will be significantly improved after short-term aging of warm mix asphalt mixture. While the water stability of warm mix asphalt pavement will be decreased significantly after freeze thawing cycle of a winter. So the Macroeconomic research(immersion Marshall test, freeze-thaw splitting)on water stability of warm mix asphalt mixture under the aging process, DSR and microscopic study of warm mix asphalt(surface energy, infrared spectroscopy) experiment were carried out. At the same time the statistical analysis methods were used to study the characteristics for water stability of asphalt mix. The main research contents and results are as follows:The Freeze-thaw Splitting and Immersion Marshall test were carried out for water stability of SK-asphalt warm mixture(Sasobit, Evotherm) under a short-term aging process(aging time of 2h/4h/8h,aging temperature of 112℃/129℃/146℃)and a long-term aging process(aging time of 7d/14d/28d/56 d,aging temperature of 60℃). The results of the study show that the water stability of WMA mixture increases with the increase of short-term aging, and its water stability will be exceed hot mix asphalt mixture in a certain aging stage. The water stability of Evotherm-WMA mixture is better than that of Sasobit-WMA mixture in the low short-term aging degree.But the increase the degree of water stability of Evotherm-WMA mixture is less than Sasobit-WMA with the increase of aging degree, the water stability of Evotherm-WMA mixture will be less than Sasobit-WMA mixture in a certain degree of aging.The water stability of Evotherm+WMA mixture will be close to Sasobit+WMA mixture with short-term aging intensifies.The water stability of WMA mixture increased at the beginning and then decreased with the increase of long-term aging. At the same time, it was also found that the residual strength of mixture of WMA and Evotherm will be over hundred.The DSR test was carried out for warm mix asphalt extracted from WMA mixture. The results show that the AI(asphalt index) increased with the increase of aging degree. The asphalt aging will happen in the aging process.The rheological behavior of warm asphalt and water stability of WMA mixture correlation was not found.The Surface Free Energy Method and Infrared spectroscopy was carried out for functional groups of warm mix asphalt with the short-term aging. The results show that warm mix asphalt SFE increased with the short-term aging, and the SFE of Evotherm-asphalt is higher than that of Sasobit-asphalt, freeze-thaw splitting strength of WMH mixture was significantly correlated with SFE, its means that water stability will be better with the SFE increased.The S=O increased slightly, but the growth rate is very low, The C=O increased with the aging, But the increase degree was almost zero. It can be seen that the aging of warm mix asphalt is very small in short-term aging process. The C=C increased with the short-term aging.Meanwhile, the C=C was significantly correlated with the freeze-thaw splitting strength ratio of WMA mixture, and the change of C=C of warm mix asphalt could be the basic reason which change of water stability during aging of WMA mixture.The research aims to reveal the variation of WAM mixture water stability, rheological properties and microstructure of warm asphalt under various aging procedures. The influence on adhesive & cohesive force in warm mix asphalt and aggregate system.It can provide theoretical and experimental evidence to evaluate objectively moisture susceptibility of WMA. And it is has important theoretical significance and reference value to control effectively moisture damage for WMA.